A Comprehensive Book on Lunar Science

First Edition, 2012

ISBN 978-81-323-4469-8

© All rights reserved.

Published by: White Word Publications 4735/22 Prakashdeep Bldg, Ansari Road, Darya Ganj, Delhi - 110002 Email: [email protected] 

Table of Contents Chapter 1 - Lunar Mare Chapter 2 - Near Side & Far Side of the Moon Chapter 3 - Lunar Craters Chapter 4 - Shackleton (Crater) & Lunar Meteorite Chapter 5 - Lunar Water Chapter 6 - Lunar Soil Chapter 7 - Transient Lunar Phenomenon Chapter 8 - Geology of the Moon Chapter 9 - Moon Rock Chapter 10 - Apollo Lunar Surface Experiments Package

Chapter- 1

Lunar Mare

Lunar nearside with major maria and craters labeled

The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and hence appear dark to the naked eye. The maria cover about 16 percent of the lunar surface, mostly on the near-side visible from Earth. The few maria on the far-side are much smaller, residing mostly in very large craters where only a small amount of flooding occurred. The traditional nomenclature for the Moon also includes one oceanus (ocean), as well as features with the names lacus (lake), palus (marsh) and sinus (bay). The latter three are smaller than maria, but have the same nature and characteristics.

Ages The ages of the mare basalts have been determined both by direct radiometric dating and by the technique of crater counting. The radiometric ages range from about 3.16 to 4.2 Ga, whereas the youngest ages determined from crater counting are about 1.2 Ga (1 Ga = 1 billion years old). Nevertheless, the majority of mare basalts appear to have erupted between about 3 and 3.5 Ga. The few basaltic eruptions that occurred on the far side are old, whereas the youngest flows are found within Oceanus Procellarum on the nearside. While many of the basalts either erupted within, or flowed into, low lying impact basins, the largest expanse of volcanic units, Oceanus Procellarum, does not correspond to any known impact basin.

Distribution of mare basalts

A global albedo map of the Moon obtained from the Clementine mission. The dark regions are the lunar maria, whereas the lighter regions are the highlands. The image is a cylindrical projection, with longitude increasing left to right from -180 E to 180 E and

latitude decreasing from top to bottom from 90 N to 90 S. The center of the image corresponds to the mean sub-Earth point, 0 N and 0 E. There are many common misconceptions concerning the spatial distribution of mare basalts. 1. Since many mare basalts fill low-lying impact basins, it was once thought that the impact event itself somehow caused the volcanic eruption. Given that mare volcanism typically occurred about 500 million years after the impact , a causal relationship is unlikely. 2. It is sometimes suggested that the gravity field of the Earth might preferentially allow eruptions to occur on the near side, but not far side. However, in a reference frame rotating with the Moon, the centrifugal acceleration is exactly equal and opposite to the gravitational acceleration of the Earth. There is thus no net force directed towards the Earth. The Earth tides do act to deform the shape of the Moon, but this shape is one of an elongated ellipsoid with high points at both the sub- and anti-Earth points. As an analogy, one should remember that there are two high tides per day on Earth, and not one. 3. Since mare basaltic magmas are denser than upper crustal anorthositic materials, basaltic eruptions might be favored at locations of low elevation where the crust is thin. However, the farside South Pole-Aitken basin contains the lowest elevations of the Moon and is yet only modestly filled by basaltic lavas. In addition, the crustal thickness beneath this basin is predicted to be much smaller than beneath Oceanus Procellarum. While crustal thickness might modulate the quantity of basaltic lavas that ultimately reach the surface, crustal thickness by itself can not be the sole factor controlling the distribution of mare basalts. 4. It is commonly suggested that there is some form of link between the synchronous rotation of the Moon about the Earth, and the mare basalts. However, gravitational torques that result in tidal despinning only arise from the moments of inertia of the body (these are directly relatable to the spherical harmonic degree-2 terms of the gravity field), and the mare basalts hardly contribute to this. (Hemispheric structures correspond to spherical harmonic degree-1, and do not contribute to the moments of inertia.) Furthermore, tidal despinning is predicted to have occurred quickly (on the order to 10s of millions of years), whereas the majority of mare basalts erupted about 1 billion years later. The reason that the mare basalts are predominantly located on the near-side hemisphere of the Moon is still being debated by the scientific community. Based on data obtained from the Lunar Prospector mission, it appears that a large proportion of the Moon's inventory of heat producing elements (in the form of KREEP) is located within the regions of Oceanus Procellarum and the Imbrium basin, a unique geochemical province now referred to as the Procellarum KREEP Terrane. While the enhancement in heat production within the Procellarum KREEP Terrane is most certainly related to the longevity and intensity of volcanism found there, the mechanism by which KREEP became concentrated within this region is not agreed upon.

Composition Mare basalts are generally grouped into three series based on their major element chemistry: high-Ti basalts, low-Ti basalts, and very Low-Ti (VLT) basalts. While these groups were once thought to be distinct based on the Apollo samples, global remote sensing data from the Clementine mission now shows that there is a continuum of titanium concentrations between these end members, and that the high-titanium concentrations are the least abundant. TiO2 abundances can reach up to 15 wt.% for mare basalts, whereas most terrestrial basalts have abundances much less than 4 wt.%. Other geochemical subdivisions are based on the abundance of aluminium and potassium.

Chapter- 2

Near Side & Far Side of the Moon

Near side of the Moon The near side of the Moon is the lunar hemisphere that is permanently turned towards the Earth, whereas the opposite side is the far side of the Moon. Only one side of the Moon is visible from Earth because the Moon rotates about its spin axis at the same rate that the Moon orbits the Earth, a situation known as synchronous rotation or tidal locking. The Moon is directly illuminated by the Sun, and the cyclically varying viewing conditions cause the lunar phases. The unilluminated portions of the Moon can sometimes be dimly seen as a result of earthshine, which is sunlight reflected off the surface of the Earth and onto the Moon. Since the Moon's orbit is both somewhat elliptical and inclined to the ecliptic plane, librations allow up to 59% of the Moon's surface to be viewed from Earth (but only half at any instant).

The names of the major seas and some craters on the near side of the Moon

Names The near side of the Moon is characterised by large dark areas that were once believed to be seas by astronomers who first mapped them in the 17th century (notably, Giovanni Battista Riccioli and Francesco Maria Grimaldi). Although it was found out later that the Moon has no seas, the term "mare" (plural: maria) are still used. The lighter toned regions are referred to as "terrae", or more commonly, the "highlands"...

Orientation

The image of the Moon here is drawn as is normally shown on maps, that is with north on top and west to the left. Astronomers usually turn the map over to have south on top, as to correspond with the view in most telescopes which also show the image upside down. Note that west and east on the Moon are where you would expect them, when standing on the Moon.. But when we, on Earth, see the Moon in the sky, then the east — west direction is just reversed. When specifying coordinates on the Moon it should therefore always be mentioned whether geographic (or rather selenographic) coordinates are used or astronomical coordinates. The actual orientation you see the Moon in the sky or on the horizon depends on your geographic latitude on Earth. In the following description a few typical cases will be considered.  

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

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On the north pole, if the Moon is visible, it stands low above the horizon with its north pole up. In mid northern latitudes (North America, Europe, Asia) the Moon rises in the east with its northeastern limb up (Mare Crisium), it reaches it highest point in the south with its north on top, and sets in the west with its northwestern limb (Mare Imbrium) on top. On the equator, when the Moon rises in the east, its N — S axis appears horizontal and Mare Foecunditatis is on top. When it sets in the west, about 12.5 hours later, the axis is still horizontal, and Oceanus Procellarum is the last area to dip below the horizon. In between these events, the Moon reached its highest point in the zenith and then its selenographic directions are lined up with those on Earth. In mid southern latitudes (South America, South Pacific, Australia, South Africa) the Moon rises in the east with its southeastern limb up (Mare Nectaris), it reaches it highest point in the north with its south on top, and sets in the west with its southwestern limb (Mare Humorum) on top. On the south pole the Moon behaves as on the north pole, but there it appears with its south pole up.

Far side of the Moon

Far side of the Moon. The far side of the Moon is the lunar hemisphere that is permanently turned away from the Earth. The far hemisphere was first photographed by the Soviet Luna 3 probe in 1959, and was first directly observed by human eyes when the Apollo 8 mission orbited the Moon in 1968. The rugged terrain is distinguished by a multitude of crater impacts, as well as relatively few lunar maria. It includes the second largest known impact feature in the Solar System, the South Pole-Aitken basin. The far side has been suggested as a potential location for a large radio telescope, as it would be shielded from possible radio

interference from Earth. To date, there has been no ground exploration of the far side of the Moon.

History Tidal forces between Earth and the Moon have slowed the moon's rotation so that the same side is always facing the Earth. The other face, which is never visible from the Earth in its entirety (18% of it can be seen under some conditions), is therefore called the "far side of the Moon". The far side should not be confused with the "dark side" (the hemisphere that is not illuminated by the Sun at a given point in time), as the two are the same only during a full moon and, during a new moon, the near side is the dark side. Both the near and far sides receive (on average) almost equal amounts of light from the Sun. However, the term "dark side of the moon" is commonly used incorrectly to refer to the far side.

Differences The two hemispheres have distinctly different appearances, with the near side covered in multiple, large maria (Latin for 'seas,' since the earliest astronomers incorrectly thought that these plains were seas of lunar water). The far side has a battered, densely cratered appearance with few maria. Only 2.5% of the surface of the far side is covered by maria, compared to 31.2% on the near side. The most likely explanation for this difference is related to a higher concentration of heat-producing elements on the near-side hemisphere, as has been demonstrated by geochemical maps obtained from the Lunar Prospector gamma-ray spectrometer. While other factors such as surface elevation and crustal thickness could also affect where basalts erupt, these do not explain why the farside South Pole-Aitken basin (which contains the lowest elevations of the Moon and possesses a thin crust) was not as volcanically active as Oceanus Procellarum on the near side. Another factor in the large difference between the two hemispheres is that the near side has been shielded from impacts by the Earth via the synchronous rotation that keeps the far side exposed to impactors coming from outer space.

Exploration

1959 USSR stamp commemorating first photographs of the far side of the Moon. Until the late 1950s little was known about properties of the far side of the Moon. Librations of the Moon periodically allowed limited glimpses of features that are located near the lunar limb on the far side. These features, however, were seen from a low angle, hindering useful observation. (It proved difficult to distinguish a crater from a mountain range.) The remaining 82% of the surface on the far side remained unknown, and its properties were subject to much speculation. An example of a far side feature that can be viewed through libration is the Mare Orientale, which is a prominent impact basin spanning almost 1,000 kilometres (600 mi),

yet this was not even named as a feature until 1906, by Julius Franz in Der Mond. The true nature of the basin was discovered in the 1960s when rectified images were projected onto a globe. It was photographed in fine detail by Lunar Orbiter 4 in 1967. On October 7, 1959 the Soviet probe, Luna 3, took the first photographs of the lunar far side, eighteen of them being resolvable ones covering one-third of the surface invisible from the Earth. The images were analysed, and the first atlas of the far side of the Moon was published by the USSR Academy of Sciences on November 6, 1960. It included a catalog of 500 distinguished features of the landscape. A year later the first globe (1:13 600 000 scale ) containing lunar features invisible from the Earth was released in the USSR, based on images from Luna 3. On July 20, 1965 another Soviet probe Zond 3 transmitted 25 pictures of very good quality of the lunar far side, with much better resolution than those from Luna 3. In particular, they revealed chains of craters, hundreds of kilometers in length. In 1967 the second part of the "Atlas of the Far Side of the Moon" was published in Moscow, based on data from Zond 3, with the catalog now including 4,000 newly discovered features of lunar far side landscape. In the same year the first "Complete Map of the Moon" (1:5 000 000 scale ) and updated complete globe (1:10 000 000 scale), featuring 95 percent of the lunar surface were released in the Soviet Union. As a lot of prominent landscape features of the far side were discovered by Soviet space probes, Soviet scientists selected names for them. This caused some controversy, and the International Astronomical Union, leaving many of those names intact, later assumed the role of naming lunar features on this hemisphere. The far side was first observed directly by human eyes during the Apollo 8 mission in 1968. Astronaut William Anders described the view:

“

The backside looks like a sand pile my kids have played in for some time. It's all beat up, no definition, just a lot of bumps and holes.

”

It has been seen by all crew members of the Apollo 8 and Apollo 10 through Apollo 17 missions since that time, and photographed by multiple lunar probes. Spacecraft passing behind the Moon were out of direct radio communication with the Earth, and had to wait until the orbit allowed transmission. During the Apollo missions, the main engine of the Service Module was fired when the vessel was behind the Moon, producing some tense moments in Mission Control before the craft reappeared.

Potential

Some of the features of the geography are labeled in this image. Because the far side of the Moon is shielded from radio transmissions from the Earth, it is considered a good location for placing radio telescopes for use by astronomers. Small, bowl-shaped craters provide a natural formation for a stationary telescope similar to Arecibo in Puerto Rico. For much larger-scale telescopes, the 100-kilometre (62 mi) diameter crater Daedalus is situated near the center of the far side, and the 3 km (2 mi)high rim would help to block stray communications from orbiting satellites. Another potential candidate for a radio telescope is the Saha crater.

Before deploying radio telescopes to the far side, several problems must be overcome. The fine lunar dust can contaminate equipment, vehicles, and space suits. The conducting materials used for the radio dishes must also be carefully shielded against the effects of solar flares. Finally the area about the telescopes must be protected against contamination by other radio sources. The L2 Lagrange point of the Earth-Moon system is located about 62,800 km (39,000 mi) above the far side, which has also been proposed as a location for a future radio telescope which would perform a Lissajous orbit about the Lagrangian point. One of the NASA missions to the Moon under study would send a sample-return lander to the South Pole-Aitken basin, the location of a major impact event that created a formation nearly 2,400 kilometres (1,491 mi) across. The size of this impact has created a deep penetration into the lunar surface, and a sample returned from this site could be analyzed for information concerning the interior of the Moon. Because the near side is partly shielded from the solar wind by the Earth, the far side maria are expected to have the highest concentration of helium-3 on the surface of the Moon. This isotope is relatively rare on the Earth, but has good potential for use as a fuel in fusion reactors. Proponents of lunar settlement have cited presence of this material as a reason for development of a Moon base.

Chapter- 3

Lunar Craters

Webb crater, as seen from Lunar Orbiter 1. Several smaller craters can be seen in and around Webb crater.

Side view of the Moltke crater taken from Apollo 11. Lunar craters are craters on Earth's Moon. The Moon's surface is saturated with craters, almost all of which were formed by impacts.

History The word crater adopted by Galileo from the Latin word for cup. Galileo built his first telescope in late 1609, and turned it to the Moon for the first time on November 30, 1609. He discovered that, contrary to general opinion at that time, the Moon was not a perfect sphere, but had both mountains and cup-like depressions, the latter of which he gave the name craters. Scientific opinion as to the origin of craters swung back and forth over the ensuing centuries. The competing theories were (a) volcanic eruptions blasting holes in the Moon, (b) meteoric impact, (c) a strange theory known as the Welteislehre developed in Germany between the two World Wars which suggested glacial action creating the craters. Evidence collected during the Apollo Project and from unmanned spacecraft of the same period proved conclusively that meteoric impact, or impact by asteroids for larger craters,

was the origin of almost all lunar craters, and by implication, most craters on other bodies as well.

Characteristics Because of the Moon's lack of water, an atmosphere, or tectonic plates, there is little erosion, and craters are found that exceed two billion years in age. The age of large craters is determined by the number of smaller craters contained within it, older craters generally accumulating more small, contained craters. The smallest craters found have been microscopic in size, found in rocks returned to Earth from the Moon. The largest crater called such is about 360 kilometers (200 miles) in diameter, located near the lunar South Pole. However, it is believed that many of the lunar maria were formed by giant impacts, with the resulting depression filled by upwelling lava. Craters typically will have some or all of the following features: 

   

a surrounding area with materials splashed out of the ground when the crater was formed; this is typically lighter in shade than older materials due to exposure to solar radiation for a lesser time raised rim, consisting of materials ejected but landing very close by crater wall, the downward-sloping portion of the crater crater floor, a more or less smooth, flat area, which as it ages accumulates small craters of its own central peak, found only in some craters with a diameter exceeding 16 miles (26 km); this is generally a splash effect caused by the kinetic energy of the impacting object being turned to heat and melting some lunar material.

Lunar crater categorization In 1978, Chuck Wood and Leif Andersson of the Lunar & Planetary Lab devised a system of categorization of lunar impact craters. They used a sampling of craters that were relatively unmodified by subsequent impacts, then grouped the results into five broad categories. These successfully accounted for about 99% of all lunar impact craters. The LPC Crater Types were as follows:   

ALC — small, cup-shaped craters with a diameter of about 10 km or less, and no central floor. The archetype for this category is 'Albategnius C'. BIO — similar to an ALC, but with small, flat floors. Typical diameter is about 15 km. The lunar crater archetype is Biot. SOS — the interior floor is wide and flat, with no central peak. The inner walls are not terraced. The diameter is normally in the range of 15–25 km. The archetype is Sosigenes.

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TRI — these complex craters are large enough so that their inner walls have slumped to the floor. They can range in size from 15–50 km in diameter. The archetype crater is Triesnecker. TYC — these are larger than 50 km, with terraced inner walls and relatively flat floors. They frequently have large central peak formations. Tycho is the archetype for this class.

Beyond a couple of hundred kilometers diameter, the central peak of the TYC class disappear and they are classed as basins.

Chapter- 4

Shackleton (Crater) & Lunar Meteorite

Shackleton (Crater) Shackleton (crater)

South lunar pole as imaged by the Diviner instrument on the Lunar Reconnaissance Orbiter. Shackleton crater is at bottom center. NASA photo. 89°54′S 0°00′E / 89.9°S 0.0°ECoordinates:

Coordinates

89°54′S 0°00′E / 89.9°S 0.0°E

Diameter

21.0 km

Depth

4.2 km

Colongitude

0° at sunrise

Eponym

Ernest Shackleton

Shackleton is an impact crater that lies at the south pole of the Moon. The peaks along the crater's rim are exposed to almost continual sunlight, while the interior is perpetually in shadow. The low-temperature interior of this crater functions as a cold trap that may capture and freeze volatiles shed during comet impacts on the Moon. Measurements by the Lunar Prospector spacecraft showed higher than normal amounts of hydrogen within the crater, which may indicate the presence of water ice. The crater is named after Ernest Shackleton, a noted Anglo-Irish explorer of the Antarctic.

Description The rotational axis of the Moon lies within Shackleton, only a few kilometers from its center. The crater is 21 km in diameter and 4.2 km deep. From the Earth, is viewed edgeon in a region of rough, cratered terrain. It is located within the South Pole-Aitken basin on a massif. The rim is slightly raised about the surrounding surface and it has an outer rampart that has been only lightly impacted. No significant craters intersect the rim, and it is sloped about 1.5° toward the direction 50–90° from the Earth. The age of the crater is about 3.6 billion years and it has been in the proximity of the south lunar pole for at least the last two billion years. Because the orbit of the Moon is tilted only 5° from the ecliptic, the interior of this crater lies in perpetual darkness. Peaks along the rim of the crater are almost continually illuminated by sunlight, spending about 80–90% of each lunar orbit exposed to the Sun. Continuously illuminated mountains have been termed peaks of eternal light and have been predicted to exist since the 1900s. The shadowed portion of the crater was imaged with the Terrain Camera of the Japanese SELENE spacecraft using the illumination of sunlight reflected off the rim. The interior of the crater consists of a symmetrical 30° slope that leads down to a 6.6 km diameter floor. The handful of craters along the interior span no more than a few hundred meters. The bottom is covered by an uneven mound-like feature that is 300 to 400 m thick. The central peak is about 200 m in height. The continuous shadows in the south polar craters cause the floors of these formations to maintain a temperature that never exceeds about 100 K. For Shackleton, the average temperature was determined to be about 90 K, reaching 88 K at the crater floor. Under these conditions, the estimated rate of loss from any ice in the interior would be 10−26 to 10−27 m/s. Any water vapor that arrives here following a cometary impact on the Moon would lie permanently frozen on or below the surface. However, the surface albedo of the crater floor matches the lunar far-side, suggesting that there is no exposed surface ice. This crater was named after Ernest Henry Shackleton, an Anglo-Irish explorer of Antarctica from 1901 until his death in 1922. The name was officially adopted by the International Astronomical Union in 1994. Nearby craters of note include Shoemaker, Haworth, de Gerlache, Sverdrup, and Faustini. Somewhat farther away, on the eastern hemisphere of the lunar near side, are the larger craters Amundsen and Scott, named after two other early explorers of the Antarctic continent.

Exploration

Shackleton Crater as imaged by Clementine. From the perspective of the Earth, this crater lies along the southern limb of the Moon, making observation difficult. Detailed mapping of the polar regions and farside of the Moon did not occur until the advent of orbiting spacecraft. Shackleton lies entirely within the rim of the immense South Pole-Aitken basin, which is one of the largest known impact formations in the Solar System. This basin is over 12 kilometers deep, and an exploration of its properties could provide useful information about the lunar interior. A neutron spectrometer on board the Lunar Prospector spacecraft detected enhanced concentrations of hydrogen close to the northern and southern lunar poles, including the crater Shackleton. At the end of this mission in July 1999, the spacecraft was crashed into the nearby crater Shoemaker in the hope of detecting from Earth-based telescopes an

impact-generated plume containing water vapor. The impact event did not produce any detectable water vapor, and this may be an indication that the hydrogen is not in the form of hydrated minerals, or that the impact site did not contain any ice. Alternatively, it is possible that the crash did not excavate deeply enough into the regolith to liberate significant quantities of water vapor. From images of the crater edge taken from orbit, Shackleton appears to be relatively intact; much like a young crater that has not been significantly eroded from subsequent impacts. This may mean that the inner sides are relatively steep, which may make traversing the sides relatively difficult for a robotic vehicle. In addition, it is possible that the interior floor might not have collected a significant quantity of volatiles since its formation. However other craters in the vicinity are considerably older, and may contain significant deposits of hydrogen, possibly in the form of water ice. Radar studies following the Lunar Prospector mission demonstrate that the inner walls of Shackleton are similar in reflective characteristics to those of some sunlit craters. In particular, the surroundings appear to contain a significant number of blocks in its ejecta blanket, suggesting that its radar properties are a result of surface roughness, and not ice deposits, as was previously suggested from a radar experiment involving the Clementine mission. This interpretation, however, is not universally agreed upon within the scientific community. Radar images of the crater at a wavelength of 13 cm show no evidence for water ice deposits. Optical imaging inside the crater was done for the first time by the Japanese lunar orbiter spacecraft Kaguya in 2007. It did not have any evidence of significant amount of water ice, down to the image resolution of 10 m per pixel. On November 15, 2008, a 34-kg probe made a hard landing near the crater. The moon impact probe (MIP) was launched from the Indian Chandrayaan-I spacecraft and reached the surface 25 minutes later. The probe carried a radar altimeter, video imaging system, and a mass spectrometer, which will be used to search for water.

Potential uses

Shackleton Crater as imaged by LRO. Some sites along Shackleton's rim receive almost constant illumination. At these locales sunlight is almost always available for conversion into electricity using solar panels, potentially making them good locations for future Moon landings. The temperature at this site is also more favorable than at more equatorial latitudes as it does not experience the daily temperature extremes of 100 °C when the Sun is overhead, to as low as −150 °C during the lunar night. While scientific experiments performed by Clementine and Lunar Prospector could indicate the presence of water in the polar craters, the current evidence is far from

definitive. There are doubts among scientists as to whether or not the hydrogen is in the form of ice, as well as to the concentration of this "ore" with depth below the surface. Resolution of this issue will require future missions to the Moon. The presence of water suggests that the crater floor could potentially be "mined" for deposits of hydrogen in water form, a commodity that is expensive to deliver directly from the Earth. This crater has also been proposed as a future site for a large infrared telescope. The low temperature of the crater floor makes it ideal for infrared observations, and solar cells placed along the rim could provide near-continuous power to the observatory. About 120 kilometers from the crater lies the 5-km tall Malapert Mountain, a peak that is perpetually visible from the Earth, and which could serve as a radio relay station when suitably equipped. NASA has named the rim of Shackleton as a potential candidate for its lunar outpost, slated to be up and running by 2020 and continuously staffed by a crew by 2024. The location would promote self-sustainability for lunar residents, as perpetual sunlight on the south pole would provide energy for solar panels. Furthermore, the shadowed polar regions are believed to contain the frozen water necessary for human consumption and could also be harvested for fuel manufacture.

Lunar meteorite

Lunar Meteorite Allan Hills 81005 A Lunar meteorite is a meteorite that is known to have originated on the Moon.

Discovery In January 1982, John Schutt, leading an expedition in Antarctica for the ANSMET program, found a meteorite that he recognized to be unusual. Shortly thereafter, the meteorite now called Allan Hills 81005 was sent to Washington, DC, where Smithsonian Institution geochemist Brian Mason recognized that the sample was unlike any other

known meteorite and resembled some rocks brought back from the Moon by the Apollo program. Several years later, Japanese scientists recognized that they had also collected a lunar meteorite, Yamato 791197, during the 1979 field season in Antarctica. About 134 lunar meteorites have been discovered so far (as of October, 2010), perhaps representing more than 50 separate meteorite falls (i.e., many of the stones are "paired" fragments of the same meteoroid). The total mass is more than 46 kg. All lunar meteorites have been found in deserts; most have been found in Antarctica, northern Africa, and the Sultanate of Oman. None have yet been found in North America, South America, or Europe. Lunar origin is established by comparing the mineralogy, the chemical composition, and the isotopic composition between meteorites and samples from the Moon collected by Apollo missions.

Transfer to Earth Most lunar meteorites are launched from the Moon by impacts making lunar craters of a few kilometers in diameter or less. No source crater of lunar meteorites has been positively identified, although there is speculation that the highly anomalous lunar meteorite Sayh al Uhaymir 169 derives from the Lalande impact crater on the Lunar nearside. Cosmic ray exposure history established with noble gas measurements have shown that all lunar meteorites were ejected from the Moon in the past 20 million years. Most left the Moon in the past 100,000 years. After leaving the Moon, most lunar meteoroids go into orbit around Earth and eventually succumb to Earth's gravity. Some meteoroids ejected from the Moon get launched into orbits around the sun. These meteoroids remain in space longer but eventually intersect the Earth's orbit and land.

Scientific relevance All six of the Apollo missions on which samples were collected landed in the central nearside of the Moon, an area that has subsequently been shown to be geochemically anomalous by the Lunar Prospector mission. In contrast, the numerous lunar meteorites are random samples of the Moon and consequently provide a more representative sampling of the lunar surface than the Apollo samples. Half the lunar meteorites, for example, likely sample material from the farside of the Moon. At the time the first meteorite from the Moon was discovered in 1982, there was speculation that some other unusual meteorites that had been found previously originated from Mars. The positive identification of lunar meteorites on Earth supported the hypothesis that meteoroid impacts on Mars could eject rocks from that planet. There are also speculations about the possibility of finding "Earth meteorites" on the surface of the Moon. This would be very interesting because in this case stones from Earth older than 3.9 billion years, which are destroyed on Earth by various geological processes, may have

survived on the Moon. Thus some scientists propose new missions to the Moon to search for ancient rocks from Earth.

History Today, about one in every thousand newly discovered meteorites is a lunar meteorite, whereas the vast majority of meteorites are from the asteroid belt. In the early 19th century most scientists believed that all meteorites were from the Moon. Although today supported only by a minority of researchers, there are also theories that tektites are from the Moon and should therefore also be regarded as lunar meteorites. However, most scientists regard such theories as outdated.

Private ownership Lunar meteorites collected in Africa and Oman are, for all practical purposes, the only source of moon rocks available for private ownership. This is because all rocks collected during the Apollo moon-landing program are property of the United States government or of other nations to which the U.S. conveyed them as gifts. Similarly, all lunar meteorites collected by the U.S. and Japanese Antarctic programs are, by treaty, held by those governments for research and education purposes only. Although there is no U.S. law specifically against the ownership of Apollo moonrocks, none has ever been (or is likely to ever be) given or sold by the U.S. government to private citizens. Even in the cases of plaques containing genuine Apollo moonrocks given in 2004 to astronauts and Walter Cronkite, NASA retained ownership of the rocks themselves. Most of the moonrocks collected by the Luna 16 probe are also unavailable for private ownership, although three tiny samples were sold at auction for $442,500 in 1993.

Chapter- 5

Lunar Water

Composite image of the Moon's south polar region, captured by NASA's Clementine probe over two lunar days. Permanently shadowed areas could harbour water ice.

Lunar water is water that is present on the Moon. Liquid water cannot persist at the Moon's surface, and water vapour is quickly decomposed by sunlight and lost to outer space. However, scientists have since the 1960s conjectured that water ice could survive in cold, permanently shadowed craters at the Moon's poles. Water, and the chemically related hydroxyl group ( · OH), can also exist in forms chemically bound to lunar minerals (rather than as free water), and evidence strongly suggests that this is indeed the case in low concentrations over much of the Moon's surface. In fact, adsorbed water is calculated to exist at trace concentrations of 10 to 1000 parts per million. Inconclusive evidence of free water ice at the lunar poles was accumulated from a variety of observations suggesting the presence of bound hydrogen. In September 2009, India's Chandrayaan-1 detected water on the Moon and hydroxyl absorption lines in reflected sunlight. In November 2009, NASA reported that its LCROSS space probe had detected a significant amount of hydroxyl group in the material thrown up from a south polar crater by an impactor; this may be attributed to water-bearing materials – what appears to be "near pure crystalline water-ice". In March 2010 NASA reported Mini-SAR radar aboard the Chandrayaan-1 detected what appear to be ice deposits at the lunar north pole, at least 600 million tonnes in sheets of relatively pure ice at least a couple meters thick. Water may have been delivered to the Moon over geological timescales by the regular bombardment of water-bearing comets, asteroids and meteoroids or continuously produced in situ by the hydrogen ions (protons) of the solar wind impacting oxygenbearing minerals. The search for the presence of lunar water has attracted considerable attention and motivated several recent lunar missions, largely because of water's usefulness in rendering long-term lunar habitation feasible.

History of observations 20th century The possibility of ice in the floors of polar lunar craters was first suggested in 1961 by Caltech researchers Kenneth Watson, Bruce C. Murray, and Harrison Brown. Although trace amounts of water were found in lunar rock samples collected by Apollo astronauts, this was assumed to be a result of contamination, and the majority of the lunar surface was generally assumed to be completely dry. However, a 2008 study of lunar rock samples revealed evidence of water molecules trapped in volcanic glass beads. The first direct evidence of water vapor near the Moon was obtained by the Apollo 14 ALSEP Suprathermal Ion Detector Experiment, SIDE, on March 7, 1971. A series of bursts of water vapor ions were observed by the instrument mass spectrometer at the lunar surface near the Apollo 14 landing site.

The first proposed evidence of water ice on the Moon came in 1994 from the United States military Clementine probe. In an investigation known as the 'bistatic radar experiment', Clementine used its transmitter to beam radio waves into the dark regions of the south pole of the Moon. Echoes of these waves were detected by the large dish antennas of the Deep Space Network on Earth. The magnitude and polarisation of these echoes was consistent with an icy rather than rocky surface, but the results were inconclusive. Resulting computer simulations suggested that an area up to 14,000 km² might be in permanent shadow and hence have the potential to harbour lunar ice. The Lunar Prospector probe, launched in 1998, employed a neutron spectrometer to measure the amount of hydrogen in the lunar regolith near the polar regions. It was able to determine hydrogen abundance and location to within 50 parts per million and detected enhanced hydrogen concentrations at the lunar north and south poles. These were interpreted as indicating significant amounts of water ice trapped in permanently shadowed craters, but could also be due to the presence of the hydroxyl radical (•OH) chemically bound to minerals. Based on data from Clementine and Lunar Prospector, NASA scientists have estimated that if surface water ice is present, the total quantity could be of the order of 1 to 3 cubic kilometers. More suspicions about the existence of water on the Moon were generated by inconclusive data produced by Cassini–Huygens mission, which passed the Moon in 1999. In July 1999, at the end of its mission, the Lunar Prospector probe was deliberately crashed into Shoemaker crater, near the Moon's south pole, in the hope that detectable quantities of water would be liberated. However, spectroscopic observations from ground-based telescopes did not reveal the spectral signature of water.

21st century Deep Impact In 2005, observations of the Moon by the Deep Impact spacecraft produced inconclusive spectroscopic data suggestive of water on the Moon. In 2006, observations with the Arecibo planetary radar showed that some of the near-polar Clementine radar returns, previously claimed to be indicative of ice, might instead be associated with rocks ejected from young craters. If true, this would indicate that the neutron results from Lunar Prospector were primarily from hydrogen in forms other than ice, such as trapped hydrogen molecules or organics. Nevertheless, the interpretation of the Arecibo data do not exclude the possibility of water ice in permanently shadowed craters. In June 2009, NASA's Deep Impact spacecraft, now redesignated EPOXI, made further confirmatory bound hydrogen measurements during another lunar flyby. Kaguya As part of its lunar mapping programme, Japan's Kaguya probe, launched in September 2007 for a 19-month mission, carried out gamma ray spectrometry observations from orbit that can measure the abundances of various elements on the Moon's surface. Japan's Kaguya probe's high resolution imaging sensors failed to detect any signs of water ice in

permanently shaded craters around the south pole of the Moon, and it ended its mission by crashing into the lunar surface in order to study the ejecta plume content. Chang'e 1 The People's Republic of China's Chang'e 1 orbiter, launched in October 2007, took the first detailed photographs of some polar areas where ice water is likely to be found.

Image of the Moon taken by the Moon Mineralogy Mapper. Blue shows the spectral signature of hydroxide, green shows the brightness of the surface as measured by reflected infrared radiation from the Sun and red shows an iron-bearing mineral called pyroxene.

On Friday 9 October 2009, as the spent upper stage of NASA's Lunar Reconnaissance Orbiter launcher smashed into the Cabeus lunar crater, the LCROSS probe attempted to detect water in the ejecta plume before it also crashed itself onto the lunar surface. Chandrayaan-1 On November 14, 2008, the Indian spacecraft Chandrayaan-1 released the Moon Impact Probe (MIP) which impacted Shackleton Crater, of the lunar south pole, at 20:31 on 14 November 2008 releasing subsurface debris that was analyzed for presence of water ice. On September 25, 2009, NASA declared that data sent from its Moon Mineralogy Mapper (M3) instrument aboard Chandrayaan-1 orbiter confirmed the existence of hydrogen over large areas of the Moon's surface, albeit in low concentrations and in the form of hydroxyl group ( · OH) chemically bound to soil. This supports earlier evidence from spectrometers aboard the Deep Impact and Cassini probes. In March 2010, it was reported that the Mini-Sar experiment onboard the Chandrayaan-1 had discovered cold

dark spots inside permanently shadowed craters which are hypotheized to potentially contain an estimated 600 million metric tons of water-ice held within northern polar craters. Lunar Reconnaissance Orbiter The search for lunar ice continued with NASA's Lunar Reconnaissance Orbiter (LRO) / LCROSS mission, launched June 18, 2009. LRO's onboard instruments carried out a variety of observations that may provide further evidence of water. On October 9, 2009, the Centaur upper stage of its Atlas V carrier rocket was directed to impact Cabeus crater at 11:31 UTC, followed shortly by the LCROSS spacecraft that flew into the ejecta plume and attempted to detect the presence of water vapor in the debris cloud. Although no immediate spectacular plume was seen, time was needed to analyze the spectrometry data. On November 13, 2009 NASA reported that after analysis of the data obtained from the ejecta plume, the spectral signature of water had been confirmed. However, what was actually detected was the chemical group hydroxyl ( · OH), which is suspected to be from water, but could also be hydrates, which are inorganic salts containing chemicallybound water molecules. The nature, concentration and distribution of this material requires further analysis; chief mission scientist Anthony Colaprete has stated that the ejecta appears to include a range of fine-grained particulates of near pure crystalline water-ice. A later definitive analysis found the concentration of water to be "5.6 ± 2.9% by mass."

Possible water cycle Production Lunar water has two potential origins: water-bearing comets (and other bodies) striking the Moon, and in situ production. It has been theorized that the latter may occur when hydrogen ions (protons) in the solar wind chemically combine with the oxygen atoms present in the lunar minerals (oxides, silicates etc.) to produce small amounts of water trapped in the minerals' crystal lattices or as hydroxyl groups, potential water precursors. (This mineral-bound water, or hydroxylated mineral surface, must not be confused with water ice.) The hydroxyl surface groups (S–OH) formed by the reaction of protons (H+) with oxygen atoms accessible at oxide surface (S=O) could further be converted in water molecules (H2O) adsorbed onto the oxide mineral's surface. The mass balance of a chemical rearrangement supposed at the oxide surface could be schematically written as follows:

2 S-OH —> S=O + S + H2O or,

2 S-OH —> S–O–S + H2O

where S represents the oxide surface. The formation of one water molecule requires the presence of two adjacent hydroxyl groups, or a cascade of successive reactions of one oxygen atom with two protons. This could constitute a limiting factor and decreases the probability of water production if the proton density per surface unit is too low.

Trapping Solar radiation would normally strip any free water or water ice from the lunar surface, splitting it into its constituent elements, hydrogen and oxygen, which then escape to space. However, because of the only very slight axial tilt of the Moon's spin axis to the ecliptic plane (1.5 °), some deep craters near the poles never receive any sunlight, and are permanently shadowed (see, for example, Shackleton crater). The temperature in these regions never rises above about 100 K (about −170 ° Celsius), and any water that eventually ended up in these craters could remain frozen and stable for extremely long periods of time — perhaps billions of years, depending on the stability of the orientation of the Moon's axis. The quantities (if any) and concentrations of this water ice are at present unknown, but it has been suggested that, at the south pole at least, any lunar ice is more likely to exist as small grains widely dispersed in the regolith rather than as thick deposits.

Transport Although free water cannot persist in illuminated regions of the Moon, any such water produced there by the action of the solar wind on lunar minerals might, through a process of evaporation and condensation, migrate to permanently cold polar areas and accumulate there as ice, perhaps in addition to any ice brought by comet impacts. The hypothetical mechanism of water transport / trapping (if any) remains unknown: indeed lunar surfaces directly exposed to the solar wind where water production occurs are too hot to allow trapping by water condensation (and solar radiation also continuously decomposes water), while no (or much less) water production is expected in the cold areas not directly exposed to the sun. Given the expected short lifetime of water molecules in illuminated regions, a short transport distance would in principle increase the probability of trapping. In other words, water molecules produced close to a cold, dark polar crater should have the highest probability of surviving and being trapped. To what extent, and at what spatial scale, direct proton exchange (protolysis) and proton surface diffusion directly occurring at the naked surface of oxyhydroxide minerals exposed to space vacuum could also play a role in the mechanism of the water transfer towards the coldest point is presently unknown and remains a conjecture.

Uses The presence of large quantities of water on the Moon would be an important factor in rendering lunar habitation cost-effective, since transporting water (or hydrogen and oxygen) from Earth would be prohibitively expensive. If future investigations find the quantities to be particularly large, water ice could be mined to provide liquid water for drinking and plant propagation, and the water could also be split into hydrogen and oxygen by solar panel-equipped electric power stations or a nuclear generator, providing breathable oxygen as well as the components of rocket fuel. The hydrogen component of the water ice could also be used to draw out the oxides in the lunar soil and harvest even more oxygen. Analysis of lunar ice would also provide scientific information about the impact history of the Moon and the abundance of comets and asteroids in the early inner solar system.

Ownership The hypothetical discovery of usable quantities of water on the Moon may raise legal questions about who owns the water and who has the right to exploit it. The United Nations Outer Space Treaty, which has not been ratified by most space-faring nations, does not prevent the exploitation of lunar resources, but does prevent the appropriation of the Moon by individual nations and is generally interpreted as barring countries from claiming ownership of in-situ resources. The Moon Treaty specifically stipulates that exploitation of lunar resources is to be governed by an "international regime", but this treaty has not been ratified by any of the major space-faring nations.

Chapter- 6

Lunar Soil

Bootprint on lunar soil

Lunar soil is the fine regolith found on the surface of the Moon. Its properties can differ significantly from those of terrestrial soil. It is essentially devoid of moisture and air, two important components found in soil on Earth. The term lunar soil is often used interchangeably with "lunar regolith" but typically refers to the finer fraction of regolith, that which is composed of grains one cm in diameter or less. Some have argued that the term "soil" is not correct in reference to the Moon because soil is defined as having organic content, whereas the Moon has none. However, standard usage among lunar scientists is to ignore that distinction. Lunar dust generally connotes even finer materials than lunar soil, the fraction which is less than 30 micrometres in diameter. Several sample return missions recovered portions of lunar rock for study on earth.

Solar weathering processes The major solar weathering processes involved in the formation of lunar soil are:    

Comminution: breaking of rocks and minerals into smaller particles; Agglutination: welding of mineral and rock fragments together by micrometeorite-impact-produced glass; Solar wind spallatation and implantation: sputtering caused by impacts of high energy particles; and Fire fountaining: deposition of dark-mantled (DM) deposits, such as the shorty crater orange soil.

Properties The significance of acquiring appropriate knowledge of lunar soil properties is great. The potential for construction of structures, ground transportation networks, and waste disposal systems, to name a few examples, will depend on real-world experimental data obtained from testing of lunar soil samples. The load-carrying capability of the soil is an important parameter in the design of such structures on Earth. Due to myriad meteorite impacts (with velocities in the range of 20 km/s), the lunar surface is covered with a thin layer of dust. The dust is electrically charged and sticks to any surface it comes in contact with. The soil becomes very dense beneath the top layer of regolith. Other factors which may affect the properties of lunar soil include large temperature differentials, the presence of a hard vacuum, and the absence of a significant lunar magnetic field (thereby allowing charged solar wind particles to continuously hit the surface of the moon). A weaker gravitational force and the absence of an atmospheric pressure are additional factors which will affect the design of structures on the surface of the Moon.

Moon fountains and electrostatic levitation The Moon appears to have a tenuous atmosphere of moving dust particles constantly leaping up from and falling back to the Moon's surface, giving rise to a "dust atmosphere" that looks static but is composed of dust particles in constant motion. The term "Moon fountain" has been used to describe this effect by analogy with the stream of molecules of water in a fountain following a ballistic trajectory while appearing static due to the constancy of the stream. According to the model recently proposed by Timothy J. Stubbs, Richard R. Vondrak, and William M. Farrell of the Laboratory for Extraterrestrial Physics at NASA's Goddard Space Flight Center, this is caused by electrostatic levitation. On the daylit side of the Moon, solar ultraviolet and X-ray radiation is energetic enough to knock electrons out of atoms and molecules in the lunar soil. Positive charges build up until the tiniest particles of lunar dust (measuring 1 micrometre and smaller) are repelled from the surface and lofted anywhere from metres to kilometres high, with the smallest particles reaching the highest altitudes. Eventually they fall back toward the surface where the process is repeated over and over again. On the night side, the dust is negatively charged by electrons in the solar wind. Indeed, the fountain model suggests that the night side would charge up to higher voltages than the day side, possibly launching dust particles to higher velocities and altitudes. This effect could be further enhanced during the portion of the Moon's orbit where it passes through Earth's magnetotail. On the terminator there could be significant horizontal electric fields forming between the day and night areas, resulting in horizontal dust transport - a form of "moon storm". This effect was also predicted in 1956 by science fiction author Hal Clement in his short story "Dust Rag" published in Astounding Science Fiction. Also in 1956, the American scientist Thomas Townsend Brown appears to have predicted a similar lofting-falling cycle of photoelectrically excited lunar dust (along with controversial and as yet unproven speculations about unusual gravitational properties of this dust, an interest he maintained to the end of his life).

lunar "twilight rays" sketched by Apollo 17 astronauts There is some evidence for this effect. In the early 1960s before Apollo 11, Surveyor 7 and several subsequent Surveyor spacecraft that soft-landed on the Moon returned photographs showing an unmistakable twilight glow low over the lunar horizon persisting after the Sun had set. Moreover, the distant horizon between land and sky did not look razor-sharp, as would have been expected in a vacuum where there was no atmospheric haze. Apollo 17 astronauts orbiting the Moon in 1972 repeatedly saw and sketched what they variously called "bands," "streamers" or "twilight rays" for about 10 seconds before lunar sunrise or lunar sunset. Such rays were also reported by astronauts aboard Apollo 8, 10, and 15. These may have been similar to crepuscular rays on Earth. Apollo 17 also placed an experiment on the Moon's surface called LEAM, short for Lunar Ejecta and Meteorites. It was designed to look for dust kicked up by small

meteoroids hitting the Moon's surface. It had three sensors that could record the speed, energy, and direction of tiny particles: one each pointing up, east, and west. LEAM saw a large number of particles every morning, mostly coming from the east or west—rather than above or below—and mostly slower than speeds expected for lunar ejecta. Also, a few hours after every lunar sunrise, the experiment's temperature rocketed so high—near that of boiling water—that LEAM had to be turned off because it was overheating. It is speculated that this could have been a result of electrically-charged moondust sticking to LEAM, darkening its surface so the experiment package absorbed rather than reflected sunlight.

Relative Concentration Of Various Elements On The Lunar Surface

Relative Concentration (in weight %) of Various Elements on Lunar Highlands, Lunar Lowlands, and Earth It's even possible that these storms have been spotted from Earth: For centuries, there have been reports of strange glowing lights on the Moon, known as "Transient lunar phenomenon" or TLPs. Some TLPs have been observed as momentary flashes—now generally accepted to be visible evidence of meteoroids impacting the lunar surface. But others have appeared as amorphous reddish or whitish glows or even as dusky hazy regions that change shape or disappear over seconds or minutes. These may have been a result of sunlight reflecting off of suspended lunar dust.

Harmful effects of lunar dust There are concerns that the dust found on the lunar surface could cause harmful effects on any manned outpost technology and crew members:   

Abrasive nature of the dust particles may rub and wear down surfaces through friction; Negative effect on coatings used on gaskets to seal equipment from space, optical lenses that include solar panels and windows as well as wiring; Possible damage to an astronaut's lungs, nervous, and cardiovascular systems.

The principles of astronautical hygiene should be used to assess the risks of exposure to lunar dust during exploration on the Moon's surface and thereby determine the most appropriate measures to control exposure. These would include for example, removing the spacesuit in a three stage airlock, vacuuming the suit before removal, using local exhaust ventilation with a high efficiency particulate filter to remove any dust in the space craft's atmosphere etc (Ref: Dr J R Cain presentation "The application of astronautical hygiene to protect the health of astronauts", UK Space Biomedicine Association Conference 2009, Downing College, University of Cambridge). The harmful properties of the lunar dust are not well known. However, based on studies of dust found on Earth, it is expected that exposure to lunar dust will result in greater risks to health both from direct exposure (acute) and if exposure is over time (chronic). This is because lunar dust is more chemically reactive and has larger surface areas composed of sharper jagged edges than Earth dust (Ref: Dr John R Cain, "Moon dust - a danger to lunar explorers" , Spaceflight, Vol 52, February 2010, pp60 - 65). If the chemical reactive particles are deposited in the lungs, they may cause respiratory disease. Long-term exposure to the dust may cause a more serious respiratory disease similar to silicosis. During lunar exploration, the astronaut's spacesuits will become contaminated with lunar dust. The dust will be released into the atmosphere when the suits are removed. The methods used to mitigate exposure will include providing high air recirculation rates in the airlock, the use of a "Double Shell Spacesuit", the use of dust shields, the use of high grade magnetic separation and the use of solar flux to sinter and melt the regolith (Ref: Dr John R Cain, "Lunar dust: the hazard and astronaut exposure risks", Earth, Moon, Planets DOI 10.1007/s11038-010-9365-0 October 2010).

Chapter- 7

Transient Lunar Phenomenon

This map, based on a survey of 300 TLPs by Barbara Middlehurst and Patrick Moore, shows the approximate distribution of observed events. Red-hued events are in red; the remainder are in yellow. A transient lunar phenomenon (TLP), or lunar transient phenomenon (LTP), is a short-lived light, color, or change in appearance on the lunar surface. Claims of short-lived phenomena go back at least 1,000 years, with some having been observed independently by multiple witnesses or reputable scientists. Nevertheless, the majority of transient lunar phenomenon reports are irreproducible and do not possess adequate control experiments that could be used to distinguish among alternative hypotheses. Few reports concerning these phenomena are ever published in peer reviewed scientific journals, the lunar scientific community rarely discusses these observations.

Most lunar scientists will acknowledge that transient events such as outgassing and impact cratering do occur over geologic time: the controversy lies in the frequency of such events. The term was created by Patrick Moore during his co-authoring of NASA Technical Report R-277 Chronological Catalog of Reported Lunar Events, published in 1968.

Description of events Reports of transient lunar phenomena range from foggy patches to permanent changes of the lunar landscape. Cameron classifies these as (1) gaseous, involving mists and other forms of obscuration, (2) reddish colorations, (3) green, blue or violet colorations, (4) brightenings, and (5) darkenings. Two extensive catalogs of transient lunar phenomena exist, with the most recent tallying 2,254 events going back to the 6th century. Of the most reliable of these events, at least one-third come from the vicinity of the Aristarchus plateau. A few of the more famous historical events of transient phenomena include the following: 

On June 18, 1178, five or more monks from Canterbury reported an upheaval on the moon shortly after sunset. "There was a bright new moon, and as usual in that phase its horns were tilted toward the east; and suddenly the upper horn split in two. From the midpoint of this division a flaming torch sprang up, spewing out, over a considerable distance, fire, hot coals, and sparks. Meanwhile the body of the moon which was below writhed, as it were, in anxiety, and, to put it in the words of those who reported it to me and saw it with their own eyes, the moon throbbed like a wounded snake. Afterwards it resumed its proper state. This phenomenon was repeated a dozen times or more, the flame assuming various twisting shapes at random and then returning to normal. Then after these transformations the moon from horn to horn, that is along its whole length, took on a blackish appearance." In 1976, Jack Hartung proposed that this described the formation of the Giordano Bruno crater.



During the night of April 19, 1787, the famous British astronomer Sir William Herschel noticed three red glowing spots on the dark part of the moon. He informed King George III and other astronomers of his observations. Herschel attributed the phenomena to erupting volcanoes and perceived the luminosity of the brightest of the three as greater than the brightness of a comet that had been discovered on April 10. His observations were made while an aurora borealis (northern lights) rippled above Padua, Italy. Aurora activity that far south from the Arctic Circle was very rare. Padua's display and Herschel's observations had happened a few days before the sunspot number had peaked in May 1787.



In 1866, the experienced lunar observer and mapmaker J. F. Julius Schmidt made the claim that Linné crater had changed its appearance. Based on drawings made

earlier by J. H. Schröter, as well as personal observations and drawings made between 1841 and 1843, he stated that the crater "at the time of oblique illumination cannot at all be seen" (his emphasis), whereas at high illumination, it was visible as a bright spot. Based on repeat observations, he further stated that "Linné can never be seen under any illumination as a crater of the normal type" and that "a local change has taken place." Today, Linné is visible as a normal young impact crater with a diameter of about 1.5 miles (2.4 km). 

On November 2, 1958, the Russian astronomer Nikolai A. Kozyrev observed an apparent half-hour "eruption" that took place on the central peak of Alphonsus crater using a 48-inch (122-cm) reflector telescope equipped with a spectrometer. During this time, the obtained spectra showed evidence for bright gaseous emission bands due to the molecules C2 and C3. While exposing his second spectrogram, he noticed "a marked increase in the brightness of the central region and an unusual white color." Then, "all of a sudden the brightness started to decrease" and the resulting spectrum was normal.



On October 29, 1963, two Aeronautical Chart and Information Center cartographers, James A. Greenacre and Edward Barr, at the Lowell Observatory, Flagstaff, Arizona, manually recorded very bright red, orange, and pink color phenomena on the southwest side of Cobra Head; a hill southeast of the lunar valley Vallis Schröteri; and the southwest interior rim of the Aristarchus crater. This event sparked a major change in attitude towards TLP reports. According to Willy Ley: "The first reaction in professional circles was, naturally, surprise, and hard on the heels of the surprise there followed an apologetic attitude, the apologies being directed at a long-dead great astronomer, Sir William Herschel." A notation by Winifred Sawtell Cameron states (1978, Event Serial No. 778): "This and their November observations started the modern interest and observing the Moon." The credibility of their findings stemmed from Greenacre's exemplary reputation as an impeccable cartographer. It is interesting to note that this monumental change in attitude had been caused by the reputations of map makers and not by the acquisition of photographic evidence.



On the night of November 1–2, 1963, a few days after Greenacre's event, at the Observatoire du Pic-du-Midi in the French Pyrenees, Zdenek Kopal and Thomas Rackham made the first photographs of a "wide area lunar luminescence." His article in Scientific American transformed it into one of the most widely publicized TLP events. Kopal, like others, had argued that Solar Energetic Particles could be the cause of such a phenomenon.



During the Apollo 11 mission Houston radioed to Apollo 11: "We've got an observation you can make if you have some time up there. There's been some lunar transient events reported in the vicinity of Aristarchus." Astronomers in Bochum, West Germany, had observed a bright glow on the lunar surface—the same sort of eerie luminescence that has intrigued moon watchers for centuries. The report was passed on to Houston and thence to the astronauts. Almost

immediately, Armstrong reported back, "Hey, Houston, I'm looking north up toward Aristarchus now, and there's an area that is considerably more illuminated than the surrounding area. It seems to have a slight amount of fluorescence." 

In 1992, Audouin Dollfus of the Observatoire de Paris reported anomalous features on the floor of Langrenus crater using a one-meter (3.2-foot) telescope. While observations on the night of December 29, 1992, were normal, unusually high albedo and polarization features were recorded the following night that did not change in appearance over the six minutes of data collection. Observations three days later showed a similar, but smaller, anomaly in the same vicinity. While the viewing conditions for this region were close to specular, it was argued that the amplitude of the observations were not consistent with a specular reflection of sunlight. The favored hypothesis was that this was the consequence of light scattering from clouds of airborne particles resulting from a release of gas. The fractured floor of this crater was cited as a possible source of the gas.

Explanations Explanations for the transient lunar phenomena fall in four classes: outgassing, impact events, electrostatic phenomena, and unfavorable observation conditions.

Outgassing Some TLPs may be caused by gas escaping from underground cavities. A number of these gaseous events are purported to display a distinctive reddish hue, while others have appeared as white clouds or an indistinct haze. The majority of TLPs appear to be associated with floor-fractured craters, the edges of lunar maria, or in other locations linked by geologists with volcanic activity. However, it should be noted that these are some of the most common targets when viewing the moon, and this correlation could be an observational bias. In support of the outgassing hypothesis, data from the Lunar Prospector alpha particle spectrometer indicate the recent outgassing of radon to the surface. In particular, results show that radon gas was emanating from the vicinity of the craters Aristarchus and Kepler during the time of this two year mission. These observations could be explained by the slow and visually imperceptible diffusion of gas to the surface, or by discrete explosive events. In support of explosive outgassing, it has been suggested that a roughly 3 km- (1.9 mi-) diameter region of the lunar surface was "recently" modified by a gas release event. However, the age of this feature is believed to be about 1 million years old, suggesting that such large phenomena occur only infrequently.

Impact events Impact events are continually occurring on the lunar surface. The most common events are those associated with micrometeorites, as might be encountered during meteor showers. Impact flashes from such events have been detected from multiple and

simultaneous Earth-based observations. Tables of impacts recorded by video cameras exist for years since 2005 many of which are associated with meteor showers. Furthermore, impact clouds were detected following the crash of ESA's SMART-1 spacecraft. , India's Moon Impact Probe and NASA's LCROSS. Impact events leave a visible scar on the surface, and these could be detected by analyzing before and after photos of sufficiently high resolution. No impact craters having formed between the Apollo-era, Clementine (global resolution 100 metre, selected areas 7-20 metre) and SMART-1 (resolution 50 metre) missions have been identified.

Electrostatic phenomena

Eight individual frames taken from a video of the lunar crater Clavius showing the effect of the Earth's atmosphere on astronomical images It has been suggested that effects related to either electrostatic charging or discharging might be able to account for some of the transient lunar phenomena. One possibility is that electrodynamic effects related to the fracturing of near-surface materials could charge any gases that might be present, such as implanted solar wind or radiogenic daughter products. If this were to occur at the surface, the subsequent discharge from this gas might be able to give rise to phenomena visible from Earth. Alternatively, it has been proposed that the triboelectric charging of particles within a gas-borne dust cloud could give rise to electrostatic discharges visible from Earth. Finally, electrostatic levitation of dust near the terminator could potentially give rise to some form of phenomenon visible from Earth.

Unfavorable observation conditions It is possible that many transient phenomena might not be associated with the moon itself but could be a result of unfavorable observing conditions or phenomena associated with the earth. For instance, some reported transient phenomena are for objects near the resolution of the employed telescopes. The Earth's atmosphere can give rise to significant temporal distortions that could be confused with actual lunar phenomena. Other nonlunar explanations include the viewing of Earth-orbiting satellites and meteors or observational error.

Are TLPs real? The most significant problem that faces reports of transient lunar phenomena is that the vast majority of these were made either by a single observer or at a single location on Earth (or both). The multitude of reports for transient phenomena occurring at the same place on the moon could be used as evidence supporting their existence. However, in the absence of eyewitness reports from multiple observers at multiple locations on Earth for the same event, these must be regarded with caution. As discussed above, an equally plausible hypothesis for the majority of these events is that they are caused by the terrestrial atmosphere. If an event were to be observed at two different places on Earth at the same time, this could be used as evidence against an atmospheric origin. One attempt to overcome the above problems with transient phenomena reports was made during the Clementine mission by a network of amateur astronomers. Several events were reported, of which four of these were photographed both beforehand and afterward by the spacecraft. However, careful analysis of these images shows no discernible differences at these sites. This does not necessarily imply that these reports were a result of observational error, as it is possible that outgassing events on the lunar surface might not leave a visible marker, but neither is it encouraging for the hypothesis that these were authentic lunar phenomena. Observations are currently being coordinated by the Association of Lunar and Planetary Observers and the British Astronomical Association to re-observe sites where transient lunar phenomena were reported in the past. By documenting the appearance of these features under the same illumination and libration conditions, it is possible to judge whether some reports were simply due to a misinterpretation of what the observer regarded as an abnormality. Furthermore, with digital images, it is possible to simulate atmospheric spectral dispersion, astronomical seeing blur and light scattering by our atmosphere to determine if these phenomena could explain some of the original TLP reports.

Chapter- 8

Geology of the Moon

Exploring Shorty crater during the Apollo 17 mission to the Moon. This was the only Apollo mission to include a geologist (Harrison Schmitt). NASA photo.

False color image of the Moon taken by the Galileo orbiter showing geological features. NASA photo.

The same image in normal color. The geology of the Moon (sometimes called selenology, although the latter term can refer more generally to "lunar science") is quite different from that of the Earth. The Moon lacks a significant atmosphere and any bodies of water, which eliminates erosion due to weather; it does not possess any form of plate tectonics, it has a lower gravity, and because of its small size, it cools more rapidly. The complex geomorphology of the lunar surface has been formed by a combination of processes, chief among which are impact cratering and volcanism. The Moon is a differentiated body, possessing a crust, mantle and core. Geological studies of the Moon are based on a combination of Earth-based telescope observations, measurements from orbiting spacecraft, lunar samples, and geophysical data. A few locations were sampled directly during the Apollo missions in the late 1960s and early 1970s, which returned approximately 385 kilograms of lunar rock and soil to

Earth, as well as several missions of the Soviet Luna programme. The Moon is the only extraterrestrial body for which we possess samples with a known geologic context. A handful of lunar meteorites have been recognized on Earth, though their source craters on the Moon are unknown. A substantial portion of the lunar surface has not been explored, and a number of geological questions remain unanswered.

Elemental composition

Relative Concentration Of Various Elements On The Lunar Surface

Relative Concentration (in weight %) of Various Elements on Lunar Highlands, Lunar Lowlands, and Earth Elements known to be present on the lunar surface include, among others, oxygen (O), silicon (Si), iron (Fe), magnesium (Mg), calcium (Ca), aluminium (Al), manganese (Mn) and titanium (Ti). Among the more abundant are oxygen, iron and silicon. The oxygen content is estimated at 45%. Carbon (C) and nitrogen (N) appear to be present only in trace quantities from deposition by solar wind. Neutron spectrometry data from the Lunar Prospector indicate the presence of hydrogen (H) concentrated at the poles.

Formation

Visible face of the Moon For a long time, the fundamental question regarding the history of the Moon was of its origin. Early hypotheses included fission from the Earth, capture, and co-accretion. Today, the giant impact hypothesis is widely accepted by the scientific community.

Fission hypothesis The idea that the early Earth, with an accelerated rotation, expelled a piece of its mass was proposed by George Darwin (son of the famous biologist Charles Darwin). It was commonly assumed that the Pacific Ocean represented the scar of this event. However, today it is known that the oceanic crust that makes up this ocean basin is relatively young, about 200 million years old or less, whereas the Moon is much older. This hypothesis cannot account for the angular momentum of the Earth-Moon system.

Lunar capture This hypothesis states that the Moon was captured, completely formed, by the gravitational field of the Earth. This is unlikely, since a close encounter with the Earth would have produced either a collision or an alteration of the trajectory of the body in

question, so if it had indeed happened, the Moon probably would never return to meet again with the Earth. For this hypothesis to function, there would have to be a large atmosphere extended around the primitive Earth, which would be able to slow the movement of the Moon before it could escape. This hypothesis is considered to explain the irregular satellite orbits of Jupiter and Saturn. In addition, this hypothesis has difficulty explaining the similar oxygen isotope ratio of the two worlds.

Co-accretion hypothesis This hypothesis states that the Earth and the Moon formed together as a double system from the primordial accretion disk of the Solar System. The problem with this hypothesis is that it does not explain the angular momentum of the Earth-Moon system, nor why the Moon has a relative small iron core compared to the Earth (25% of its radius compared to 50% for the Earth).

Giant impact theory At present the best explanation for the origin of the Moon involves a collision of two protoplanetary bodies during the early accretional period of Solar System evolution. This "giant impact theory", which became popular in 1984 (although Reginald Aldworth Daly, a Canadian professor at Harvard college, originated it in the 1940s), satisfies the orbital conditions of the Earth and Moon and can account for the relatively small metallic core of the Moon. Collisions between planetesimals are now recognized to lead to the growth of planetary bodies early in the evolution of the Solar System, and in this framework it is inevitable that large impacts will sometimes occur when the planets are nearly formed. The theory requires a collision between a body about 90% the present size of the Earth, and another the diameter of Mars (half of the terrestrial radius and a tenth of its mass). The colliding body has sometimes been referred to as Theia, the mother of Selene, the Moon goddess in Greek mythology. This size ratio is needed in order for the resulting system to possess sufficient angular momentum to match the current orbital configuration. Such an impact would have put enough material into orbit about the Earth to have eventually accumulated to form the Moon. Computer simulations of this event appear to show that the collision must occur with a somewhat glancing blow. This will cause a small portion of the colliding body to form a long arm of material that will then shear off. The asymmetrical shape of the Earth following the collision then causes this material to settle into an orbit around the main mass. The energy involved in this collision is impressive: trillions of tons of material would have been vaporized and melted. In parts of the Earth the temperature would have risen to 10,000°C (18,000°F). This formation theory helps explain why the Moon possesses only a small iron core (roughly 25% of its radius, in comparison to about 50% for the Earth). Most of the iron core from the impacting body is predicted to have accreted to the core of the Earth. The lack of volatiles in the lunar samples is also explained in part by the energy of the

collision. The energy liberated during the reaccreation of material in orbit about the Earth would have been sufficient to melt a large portion of Moon, leading to the generation of a magma ocean. The newly formed moon orbited at about one-tenth the distance that it does today, and became tidally-locked with the Earth, where one side continually faces toward the Earth. The geology of the Moon has since been independent of the Earth. While this theory explains many aspects of the Earth-Moon system, there are still a few unresolved problems facing this theory, such as the Moon's volatile elements not being as depleted as expected from such an energetic impact.

Geologic history The geological history of the Moon has been defined into six major epochs, called the lunar geologic timescale. Starting about 4.5 billion years ago, the newly formed Moon was in a molten state and was orbiting much closer to the Earth. The resulting tidal forces deformed the molten body into an ellipsoid, with the major axis pointed towards Earth. The first important event in the geologic evolution of the Moon was the crystallization of the near global magma ocean. It is not known with certainty what its depth was, but several studies imply a depth of about 500 km or greater. The first minerals to form in this ocean were the iron and magnesium silicates olivine and pyroxene. Because these minerals were denser than the molten material around them, they sank. After crystallization was about 75% complete, less dense anorthositic plagioclase feldspar crystallized and floated, forming an anorthositic crust about 50 km in thickness. The majority of the magma ocean crystallized quickly (within about 100 million years or less), though the final remaining KREEP-rich magmas, which are highly enriched in incompatible and heat producing elements, could have remained partially molten for several hundred million (or perhaps 1 billion) years. It appears that the final KREEP-rich magmas of the magma ocean eventually became concentrated within the region of Oceanus Procellarum and the Imbrium basin, a unique geologic province that is now known as the Procellarum KREEP Terrane. Quickly after the lunar crust formed, or even as it was forming, different types of magmas that would give rise to the Mg-suite norites and troctolites began to form, although the exact depths at which this occurred are not known precisely. Recent theories suggest that Mg-suite plutonism was largely confined to the region of the Procellarum KREEP Terrane, and that these magmas are genetically related to KREEP in some manner, though their origin is still highly debated in the scientific community. The oldest of the Mg-suite rocks have crystallization ages of about 3.85 Ga. However, the last large impact that could have excavated deep into the crust (the Imbrium basin) also occurred at 3.85 Ga before present. Thus, it seems probable that Mg-suite plutonic activity continued for a much longer time, and that younger plutonic rocks exist deep below the surface. Analysis of the lunar samples seem to imply that a significant percentage of the lunar impact basins formed within a very short period of time between about 4 and 3.85 Ga

ago. This hypothesis is referred to as the lunar cataclysm or late heavy bombardment. However, it is now recognized that ejecta from the Imbrium impact basin (one of the youngest large impact basins on the Moon) should be found at all of the Apollo landing sites. It is thus possible that ages for some impact basins (in particular Mare Nectaris) could have been mistakenly assigned the same age as Imbrium. The lunar maria represent ancient flood basaltic eruptions. In comparison to terrestrial lavas, these contain higher iron abundances, have low viscosities, and some contain highly elevated abundances of the titanium-rich mineral ilmenite. The majority of basaltic eruptions occurred between about 3 and 3.5 Ga ago, though some mare samples have ages as old as 4.2 Ga, and the youngest (based on the method of crater counting) are believed to have erupted only 1 billion years ago. Along with mare volcanism came pyroclastic eruptions, which launched molten basaltic materials hundreds of kilometres away from the volcano. A large portion of the mare formed, or flowed into, the low elevations associated with the nearside impact basins. However, it must be noted that Oceanus Procellarum does not correspond to any known impact structure, and the lowest elevations of the Moon within the farside South Pole-Aitken basin are only modestly covered by mare. Impacts by meteorites and comets are the only abrupt geologic force acting on the Moon today, though the variation of Earth tides on the scale of the Lunar anomalistic month causes small variations in stresses. Some of the most important craters used in lunar stratigraphy formed in this recent epoch. For example, the crater Copernicus, which has a depth of 3.76 km and a radius of 93 km, is believed to have formed about 900 million years ago (though this is debatable). The Apollo 17 mission landed in an area in which the material coming from the crater Tycho might have been sampled. The study of these rocks seem to indicate that this crater could have formed 100 million years ago, though this is debatable as well. The surface has also experienced space weathering due to high energy particles, solar wind implantation, and micrometeorite impacts. This process causes the ray systems associated with young craters to darken until it matches the albedo of the surrounding surface. However, if the composition of the ray is different from the underlying crustal materials (as might occur when a "highland" ray is emplaced on the mare), the ray could be visible for much longer times. After resumption of Lunar exploration in the 1990s, it was discovered there are scarps across the globe which are caused by the contraction due to cooling of the Moon.

Lunar landscape The lunar landscape is characterized by impact craters, their ejecta, a few volcanoes, hills, lava flows and depressions filled by magma.

A photograph of full moon taken from Earth

The highlands The most distinctive aspect of the Moon is the contrast between its light and dark zones. Lighter surfaces are the lunar highlands, which receive the name of terrae (singular terra, from the Latin for Earth), and the darker plains are called maria (singular mare, from the Latin for sea), after Johannes Kepler who introduced the name in the 17th century. The highlands are anorthositic in composition, whereas the maria are basaltic. The maria often coincide with the "lowlands," but it is important to note that the lowlands (such as within the South Pole-Aitken basin) are not always covered by maria. The highlands are older than the visible maria, and hence are more heavily cratered.

The maria The major products of volcanic processes on the Moon are evident to the Earth-bound observer in the form of the lunar maria. These are large flows of basaltic lava that correspond to low-albedo surfaces covering nearly a third of the near side. Only a few percent of the farside has been affected by mare volcanism. Even before the Apollo missions confirmed it, most scientists believed that the maria were lava-filled plains, since they possessed lava flow patterns and collapses attributed to lava tubes. The ages of the mare basalts have been determined both by direct radiometric dating and by the technique of crater counting. The oldest radiometric ages are about 4.2 Ga, whereas the youngest ages determined from crater counting are about 1 Ga (1 Ga = 1 billion years). Volumetrically, most of the mare formed between about 3 and 3.5 Ga before present. The youngest lavas erupted within Oceanus Procellarum, whereas some of the oldest appear to be located on the farside. The maria are clearly younger than the surrounding highlands given their lower density of impact craters.

Volcanic rilles near the crater Prinz

Volcanic domes within the Mons Rümker complex

Wrinkle ridges within the crater Letronne

Rima Ariadaeus is a graben. NASA photo taken during Apollo 10 mission. A large portion of maria erupted within, or flowed into, the low-lying impact basins on the lunar nearside. Nevertheless, it is unlikely that a causal relationship exists between the impact event and mare volcanism because the impact basins are much older (by about 500 million years) than the mare fill. Furthermore, Oceanus Procellarum, which is the largest expanse of mare volcanism on the Moon, does not correspond to any known impact basin. It is commonly suggested that the reason the mare only erupted on the nearside is that the nearside crust is thinner than the farside. While crustal thickness variations might act to modulate the amount of magma that ultimately reaches the surface, this hypothesis does not explain why the farside South Pole-Aitken basin, whose crust is thinner than Oceanus Procellarum, was only modestly filled by volcanic products. Finally, it should be noted that the Earth's gravity played no preferential role in causing mare volcanism to occur on the near side, as the Earth's gravitational attraction is exactly balanced by the centrifugal acceleration resulting from the Moon's rotation.

Another type of deposit associated with the maria, although it also covers the highland areas, are the "dark mantle" deposits. These deposits cannot be seen with the naked eye, but they can be seen in images taken from telescopes or orbiting spacecraft. Before the Apollo missions, scientists believed that they were deposits produced by pyroclastic eruptions. Some deposits appear to be associated with dark elongated ash cones, reinforcing the idea of pyroclasts. The existence of pyroclastic eruptions was later confirmed by the discovery of glass spherules similar to those found in pyroclastic eruptions here on Earth. Many of the lunar basalts contain small holes called vesicles, which were formed by gas bubbles exsolving from the magma at the vacuum conditions encountered at the surface. It is not known with certainty which gases escaped these rocks, but carbon monoxide is one candidate. The samples of pyroclastic glasses are of green, yellow, and red tints. The difference in color indicates the concentration of titanium that the rock possesses, with the green particles having the lowest concentrations (about 1%), and red particles having the highest concentrations (up to 14%, much more than the basalts with the highest concentrations). Rilles Rilles on the Moon sometimes resulted from the formation of localized lava channels. These generally fall into three categories, consisting of sinuous, arcuate, or linear shapes. By following these meandering rilles back to their source, they often lead to an old volcanic vent. One of the most notable sinuous rilles is the Vallis Schröteri feature, located in the Aristarchus plateau along the eastern edge of Oceanus Procellarum. An example of a sinuous rille exists at the Apollo 15 landing site, Rima Hadley, located on the rim of the Imbrium Basin. Based on observations from the mission, it is generally believed that this rille was formed by volcanic processes, a topic long debated before the mission took place. Domes A variety of shield volcanoes can be found in selected locations on the lunar surface, such as on Mons Rümker. These are believed to be formed by relatively viscous, possibly silica-rich lava, erupting from localized vents. The resulting lunar domes are wide, rounded, circular features with a gentle slope rising in elevation a few hundred meters to the mid-point. They are typically 8–12 km in diameter, but can be up to 20 km across. Some of the domes contain a small pit at their peak. Wrinkle ridges Wrinkle ridges are features created by compressive tectonic forces within the maria. These features represent buckling of the surface and form long ridges across parts of the

maria. Some of these ridges may outline buried craters or other features beneath the maria. A prime example of such an outlined feature is the crater Letronne. Grabens Grabens are tectonic features that form under extension stresses. Structurally, they are composed of two normal faults, with a down-dropped block between them. Most grabens are found within the lunar maria near the edges of large impact basins.

Impact craters

Mare Imbrium and the crater Copernicus. NASA photo. It may be surprising to learn that the origin of the Moon's craters as impact features became widely accepted only in the 1940s. This realization allowed the impact history of the Moon to be gradually worked out by means of the geologic principle of superposition. That is, if a crater (or its ejecta) overlaid another, it must be the younger. The amount of erosion experienced by a crater was another clue to its age, though this is more subjective. Adopting this approach in the late 1950s, Gene Shoemaker took the

systematic study of the Moon away from the astronomers and placed it firmly in the hands of the lunar geologists. Impact cratering is the most notable geological process on the Moon. The craters are formed when a solid body, such as an asteroid or comet, collides with the surface at a high velocity (mean impact velocities for the Moon are about 17 km per second). The kinetic energy of the impact creates a compression shock wave that radiates away from the point of entry. This is succeeded by a rarefaction wave, which is responsible for propelling most of the ejecta out of the crater. Finally there is a hydrodynamic rebound of the floor that can create a central peak. These craters appear in a continuum of diameters across the surface of the Moon, ranging in size from tiny pits to the immense South Pole-Aitken Basin with a diameter of nearly 2,500 km and a depth of 13 km. In a very general sense, the lunar history of impact cratering follows a trend of decreasing crater size with time. In particular, the largest impact basins were formed during the early periods, and these were successively overlaid by smaller craters. The size frequency distribution (SFD) of crater diameters on a given surface (that is, the number of craters as a function of diameter) approximately follows a power law with increasing number of craters with decreasing crater size. The vertical position of this curve can be used to estimate the age of the surface.

The lunar crater King displays the characteristic features of a large impact formation, with a raised rim, slumped edges, terraced inner walls, a relatively flat floor with some hills, and a central ridge. The Y-shaped central ridge is unusually complex in form. NASA photo. The most recent impacts are distinguished by well-defined features, including a sharpedged rim. Small craters tend to form a bowl shape, while larger impacts can have a central peak with flat floors. Larger craters generally display slumping features along the inner walls that can form terraces and ledges. The largest impact basins, the multiring basins, can even have secondary concentric rings of raised material. The impact process excavates high albedo materials that initially gives the crater, ejecta, and ray system a bright appearance. The process of space weathering gradually decreases the albedo of this material such that the rays fade with time. Gradually the crater and its ejecta undergo impact erosion from micrometeorites and smaller impacts. This erosional process softens and rounds the features of the crater. The crater can also be covered in ejecta from other impacts, which can submerge features and even bury the central peak.

The ejecta from large impacts can include larges blocks of material that reimpact the surface to form secondary impact craters. These craters are sometimes formed in clearly discernible radial patterns, and generally have shallower depths than primary craters of the same size. In some cases an entire line of these blocks can impact to form a valley. These are distinguished from catena, or crater chains, which are linear strings of craters that are formed when the impact body breaks up prior to impact. Generally speaking, a lunar crater is roughly circular in form. Laboratory experiments at NASA's Ames Research Center have demonstrated that even very low-angle impacts tend to produce circular craters, and that elliptical craters start forming at impact angles below five degrees. However, a low angle impact can produce a central peak that is offset from the mid-point of the crater. Additionally, the ejecta from oblique impacts show distinctive patterns at different impact angles: asymmetry starting around 60˚ and a wedge-shaped "zone of avoidance" free of ejecta in the direction the projectile came from starting around 45˚. Dark-halo craters are formed when an impact excavates lower albedo material from beneath the surface, then deposits this darker ejecta around the main crater. This can occur when an area of darker basaltic material, such as that found on the maria, is later covered by lighter ejecta derived from more distant impacts in the highlands. This covering conceals the darker material below, which is later excavated by subsequent craters. The largest impacts produced melt sheets of molten rock that covered portions of the surface which could be as thick as a kilometer. Examples of such impact melt can be seen in the northeastern part of the Mare Orientale impact basin.

Regolith The surface of the Moon has been subject to billions of years of collisions with both small and large asteroidal and cometary materials. Over time, these impact processes have pulverized and "gardened" the surface materials, forming a fine grained layer termed "regolith". The thickness of the regolith varies between 2 meters beneath the younger maria, to up to 20 meters beneath the oldest surfaces of the lunar highlands. The regolith is predominantly composed of materials found in the region, but also contains traces of materials ejected by distant impact craters. The term "mega-regolith" is often used to describe the heavily fractured bedrock directly beneath the near-surface regolith layer. The regolith contains rocks, fragments of minerals from the original bedrock, and glassy particles formed during the impacts. In most of the lunar regolith, half of the particles are made of mineral fragments fused by the glassy particles; these objects are called agglutinates. The chemical composition of the regolith varies according to its location; the regolith in the highlands is rich in aluminium and silica, just as the rocks in those regions. The regolith in the maria is rich in iron and magnesium and is silica-poor, as the basaltic rocks from which it is formed.

The lunar regolith is very important because it also stores information about the history of the Sun. The atoms that compose the solar wind – mostly helium, neon, carbon and nitrogen – hit the lunar surface and insert themselves into the mineral grains. Upon analyzing the composition of the regolith, particularly its isotopic composition, it is possible to determine if the activity of the Sun has changed with time. The gases of the solar wind could be useful for future lunar bases, since oxygen, hydrogen (water), carbon and nitrogen are not only essential to sustain life, but are also potentially very useful in the production of fuel. The composition of the lunar regolith can also be used to infer its source origin.

Lunar lava tubes Lunar lava tubes form a potentially important location for constructing a future lunar base, which may be used for local exploration and development, or as a human outpost to serve exploration beyond the Moon. A lunar lava cave potential has long been suggested and discussed in literature and thesis. Any intact lava tube on the moon could serve as a shelter from the severe environment of the lunar surface, with its frequent meteorite impacts, high-energy ultraviolet radiation and energetic particles, and extreme diurnal temperature variations. . Following the launch of the Lunar Reconnaissance Orbiter, many lunar lava tubes have been imaged. These lunar pits are found in several locations across the moon, including Marius Hills, Mare Ingenii and Mare Tranquillitatis.

The lunar magma ocean The first rocks brought back by Apollo 11 were basalts. Although the mission landed on Mare Tranquillitatis, a few millimetric fragments of rocks coming from the highlands were picked up. These are composed mainly of plagioclase feldspar; some fragments were composed exclusively of anorthositic plagioclase. The identification of these mineral fragments led to the bold hypothesis that a large portion of the Moon was once molten, and that the crust formed by fractional crystallization of this magma ocean. A natural outcome of the giant impact event is that the materials that reaccreted to form the Moon must have been hot. Current models predict that a large portion of the Moon would have been molten shortly after the Moon formed, with estimates for the depth of this magma ocean ranging from about 500 km to full moon melting. Crystallization of this magma ocean would have given rise to a differentiated body with a compositionally distinct crust and mantle and accounts for the major suites of lunar rocks. As crystallization of the lunar magma ocean proceeded, minerals such as olivine and pyroxene would have precipitated and sank to form the lunar mantle. After crystallization was about three-quarters complete, anorthositic plagioclase would have begun to crystallize, and because of its low density, float, forming an anorthositic crust. Importantly, elements that are incompatible (i.e., those that partition preferentially into the liquid phase) would have been progressively concentrated into the magma as crystallization progressed, forming a KREEP-rich magma that initially should have been sandwiched between the crust and mantle. Evidence for this scenario comes from the

highly anorthositic composition of the lunar highland crust, as well as the existence of KREEP-rich materials.

Lunar rocks Surface materials The Apollo program brought back 381.7 kg (841.5 lb) of lunar surface material, most of which is stored at the Lunar Receiving Laboratory in Houston, Texas. These rocks have proved to be invaluable in deciphering the geologic evolution of the Moon. Lunar rocks are in large part made of the same common rock forming minerals as found on Earth, such as olivine, pyroxene, and plagioclase feldspar (anorthosite). Plagioclase feldspar is mostly found in the lunar crust, while pyroxene and olivine are typically seen in the lunar mantle. The mineral ilmenite is highly abundant in some mare basalts, and a new mineral named armalcolite (named for Armstrong, Aldrin, and Collins, the three members of the Apollo 11 crew) was first discovered in the lunar samples. The maria are composed predominantly of basalt, whereas the highland regions are ironpoor and composed primarily of anorthosite, a rock composed primarily of calcium-rich plagioclase feldspar. Another significant component of the crust are the igneous Mg-suite rocks, such as the troctolites, norites, and KREEP-basalts. These rocks are believed to be genetically related to the petrogenesis of KREEP. Composite rocks on the lunar surface often appear in the form of breccias. Of these, the subcategories are called fragmental, granulitic, and impact-melt breccias, depending on how they were formed. The mafic impact melt breccias, which are typified by the low-K Fra Mauro composition, have a higher proportion of iron and magnesium than typical upper crust anorthositic rocks, as well as higher abundances of KREEP.

Composition of the maria The main characteristics of the basaltic rocks with respect to the rocks of the lunar highlands is that the basalts contain higher abundances of olivine and pyroxene, and less plagioclase. They are more rich in iron than terrestrial basalts, and also have lower viscosities. Some of them have high abundances of a ferro-titanic oxide called ilmenite. Since the first sampling of rocks contained a high content of ilmenite and other related minerals, they received the name of "high titanium" basalts. The Apollo 12 mission returned to Earth with basalts of lower titanium concentrations, and these were dubbed "low titanium" basalts. Subsequent missions, including the Soviet unmanned probes, returned with basalts with even lower concentrations, now called "very low titanium" basalts. The Clementine space probe returned data showing that the mare basalts possess a continuum in titanium concentrations, with the highest concentration rocks being the least abundant.

Internal structure of the Moon The current model of the interior of the Moon was derived using seismometers left behind during the manned Apollo program missions, as well as investigations of the Moon's gravity field and rotation. The mass of the Moon is sufficient to eliminate any voids within the interior, so it is believed to be composed of solid rock throughout. Its low bulk density (~3346 kg m−3) indicates a low metal abundance. Mass and moment of inertia constraints indicate that the Moon likely has an iron core that is less than about 450 km in radius. Studies of the Moon's physical librations (small perturbations to its rotation) furthermore indicate that the core is still molten. Most planetary bodies and moons have iron cores that are about half the size of the body. The Moon is thus anomalous in possessing a core whose size is only about one quarter of its radius. The crust of the Moon is on average about 50 km thick (though this is uncertain by about ±15 km). It is widely believed that the far-side crust is on average thicker than the near side by about 15 km. Seismology has constrained the thickness of the crust only near the Apollo 12 and 14 landing sites. While the initial Apollo-era analyses suggested a crustal thickness of about 60 km at this site, recent reanalyses of this data set suggest a thinner value, somewhere between about 30 and 45 km. Compared to that of Earth, the Moon has only a very weak external magnetic field. Other major differences are that the Moon does not currently have a dipolar magnetic field (as would be generated by a geodynamo in its core), and the magnetizations that are present are almost entirely crustal in origin. One hypothesis holds that the crustal magnetizations were acquired early in lunar history when a geodynamo was still operating. The small size of the lunar core, however, is a potential obstacle to this theory. Alternatively, it is possible that on airless bodies such as the Moon, transient magnetic fields could be generated during impact processes. In support of this, it has been noted that the largest crustal magnetizations appear to be located near the antipodes of the largest impact

basins. While the Moon does not possess a dipolar magnetic field like the Earth does, some of the returned rocks possess strong magnetizations. Furthermore measurements from orbit show that some portions of the lunar surface are associated with strong magnetic fields.

Chapter- 9

Moon Rock

Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). Collected by Apollo 16 from the Lunar Highlands near Descartes Crater. This sample is currently on display at the National Museum of Natural History in Washington, DC.

lunar sample collection case on display at the National Air and Space Museum

Lunar Sample Year Mission Returned Apollo 22 kg 1969 11 Apollo 34 kg 1969 12 Apollo 43 kg 1971 14 Apollo 77 kg 1971 15 Apollo 95 kg 1972 16 Apollo 111 kg 1972 17 Luna 16 101 g 1970 Luna 20 55 g 1972 Luna 24 170 g 1976

Moon rock describes rock that formed on the Earth's moon. The term is also loosely applied to other lunar materials collected during the course of human exploration of the Moon. The rocks collected from the Moon are measured by radiometric dating techniques. They range in age from about 3.16 billion years old for the basaltic samples derived from the lunar maria, up to about 4.5 billion years old for rocks derived from the highlands. Based on the age dating technique of "crater counting," the youngest basaltic eruptions are believed to have occurred about 1.2 billion years ago, but scientists do not possess samples of these lavas. In contrast, the oldest ages of rocks from the Earth are between 3.8 and 4.28 billion years old. There are currently three sources of Moon rocks on Earth: 1) those collected by US Apollo missions; 2) samples returned by the Soviet Union Luna missions; and 3) rocks that were ejected naturally from the lunar surface by cratering events and subsequently fell to Earth as lunar meteorites. During the six Apollo surface excursions, 2,415 samples weighing 382 kg (842 lb) were collected, the majority by Apollo 15, 16, and 17. The three Luna spacecraft returned with an additional 0.32 kg (0.7 lb) of samples. Since 1980, over 120 lunar meteorites representing about 60 different meteorite fall events (none witnessed) have been collected on Earth, with a total mass of over 48 kg. About one third of these were discovered by American and Japanese teams searching for Antarctic meteorites (e.g., ANSMET), with most of the remainder having been discovered by anonymous collectors in the desert regions of northern Africa and Oman. Almost all lunar rocks are depleted in volatiles (such as potassium or sodium) and are completely lacking in the minerals found in Earth's water. In some regards, lunar rocks

are closely related to Earth's rocks in their composition of the element oxygen. The Apollo moon rocks were collected using a variety of tools, including hammers, rakes, scoops, tongs, and core tubes. Most were photographed prior to collection to record the condition in which they were found. They were placed inside sample bags and then a Special Environmental Sample Container for return to the Earth to protect them from contamination. In contrast to the Earth, large portions of the lunar crust appear to be composed of rocks with high concentrations of the mineral anorthite. The mare basalts have relatively high iron values. Furthermore, some of the mare basalts have very high levels of titanium (in the form of ilmenite). A new mineral found on the Moon was armalcolite, named for the three astronauts on the Apollo 11 mission: Armstrong, Aldrin, and Collins.

Curation and availability

Genesis Rock returned by the Apollo 15 mission.

Samples in Lunar Sample Building at JSC

Moon rock on display for visitors to touch at the Apollo/Saturn V Center

The main repository for the Apollo moon rocks is the Lunar Sample Building at the Lyndon B. Johnson Space Center in Houston, Texas. For safe keeping, there is also a smaller collection stored at Brooks Air Force Base in San Antonio, Texas. Most of the rocks are stored in nitrogen to keep them free of moisture. They are only handled indirectly, using special tools. Moon rocks collected during the course of lunar exploration are currently considered priceless. In 1993, three small fragments from Luna 16, weighing 0.2 g, were sold for US$ 442,500. In 2002, a safe, containing minute samples of lunar and Martian material, was stolen from the Lunar Sample Building. The samples were recovered; in 2003, during the court case, NASA estimated the value of these samples at about $1 million for 285 g (10 oz) of material. Moon rocks in the form of lunar meteorites, although expensive, are widely sold and traded among private collectors. Approximately two hundred small samples were mounted and presented to national governments and U.S. governors. At least one of these was later stolen, sold, and recovered. Other samples went to selected museums, including the National Air and Space Museum, the Kansas Cosmosphere and Space Center, the Ontario Science Centre, and to the visitor center at Kennedy Space Center where it is possible to "touch a piece of the moon," which is in fact a small moon rock cemented in a pillar in the center of a bank vault that is toured by visitors. The Tribune Tower in Chicago has a small piece in a display case facing Michigan Ave. The Space Window in Washington National Cathedral incorporates a small moon rock within its stained glass. NASA says that almost 295 kg (650 lb) of the original 382 kg (842 lb) of samples are still in pristine condition in the vault at Johnson Space Center. NASA has made a number of educational packs comprising a disc of six small rock and soil samples in a lucite disc and a pack of thin petrological sections. They are available for exhibition and educational purposes in many countries, including Great Britain, where the samples are kept by the Science and Technology Facilities Council.

Classification Moon rocks fall into two main categories, the ones found in the lunar highlands (terrae) or the maria. The terrae consist dominantly of mafic plutonic rocks. Regolith breccias with similar protoliths are also common. Mare basalts come in three distinct series in direct relation to their chemistry: high-Ti basalts, low-Ti basalts, and Very Low-Ti (VLT) basalts.

Highlands lithologies

Processing facility in Lunar Sample Building at JSC

Slice of moon rock at the National Air and Space Museum in Washington, DC Mineral composition of Highland rocks Plagioclase Pyroxene Olivine Ilmenite Anorthosite 90%

5%

5%

0%

Norite

60%

35%

5%

0%

Troctolite

60%

5%

35%

0%

Mineral composition of mare basalts Plagioclase Pyroxene Olivine Ilmenite High titanium content

30%

54%

3%

18%

Low titanium content

30%

60%

5%

5%

Very low titanium content 35%

55%

8%

2%

Common lunar minerals Mineral

Elements

Lunar rock

appearance White to Calcium (Ca) transparent Plagioclase Aluminium (Al) gray; usually feldspar Silicon (Si) as elongated Oxygen (O) grains. Maroon to black; the grains appear Iron (Fe), Magnesium (Mg) more elongated in Pyroxene Calcium (Ca) the maria and Silicon (Si) more square Oxygen (O) in the highlands.

Olivine

Greenish color; Iron (Fe) Magnesium (Mg) generally, it appears in a Silicon (Si) rounded Oxygen (O) shape.

Iron (Fe), Ilmenite Titanium (Ti) Oxygen (O)

Black, elongated square crystals.

Primary igneous rocks in the lunar highlands compose three distinct groups: the ferroan anorthosite suite, the magnesian suite, and the alkali suite. Lunar breccias, formed largely by the immense basin-forming impacts, are dominantly composed of highland lithologies because most mare basalts post-date basin formation (and largely fill these impact basins). The ferroan anorthosite suite consists almost exclusively of the rock anorthosite (>90% calcic plagioclase) with less common anorthositic gabbro (70-80% calcic plagioclase, with minor pyroxene). The ferroan anorthosite suite is the most common group in the highlands, and is inferred to represent plagioclase flotation cumulates of the lunar magma ocean, with interstitial mafic phases formed from trapped interstitial melt or rafted upwards with the more abundant plagioclase framework. The plagioclase is extremely calcic by terrestrial standards, with molar anorthite contents of 94-96% (An94-96). This reflects the extreme depletion of the bulk moon in alkalis (Na, K) as well as water and other volatile elements. In contrast, the mafic minerals in this suite have low Mg/Fe ratios

that are inconsistent with calcic plagioclase compositions. Ferroan anorthosites have been dated using the internal isochron method at "circa" 4.4 Ga. The magnesian suite (or "mg suite") consists of dunites (>90% olivine), troctolites (olivine-plagioclase), and gabbros (plagioclase-pyroxene) with relatively high Mg/Fe ratios in the mafic minerals and a range of plagioclase compositions that are still generally calcic (An86-93). These rocks represent later intrusions into the highlands crust (ferroan anorthosite) at round 4.3-4.1 Ga. An interesting aspect of this suite is that analysis of the trace element content of plagioclase and pyroxene require equilibrium with a KREEP-rich magma, despite the refractory major element contents. The alkali suite is so-called because of its high alkali content -- for moon rocks. The alkali suite consists of alkali anorthosites with relatively sodic plagioclase (An70-85), norites (plagioclasse-orthopyroxene), and gabbronorites (plagioclase-clinopyroxeneorthopyroxene) with similar plagioclase compositions and mafic minerals more iron-rich than the magnesian suite. The trace element contents of these minerals also indicates a KREEP-rich parent magma. The alkali suite spans an age range similar to the magnesian suite. Lunar granites are relatively rare rocks that include diorites, monzodiorites, and granophyres. They consist of quartz, plagioclase, orthoclase or alkali feldspar, rare mafics (pyroxene), and rare zircon. The alkali feldspar may have unusual compositions unlike any terrestrial feldspar, and they are often Ba-rich. These rocks apparently form by the extreme fractional crystallization of magnesian suite or alkali suite magmas, although liquid immiscibility may also play a role. U-Pb date of zircons from these rocks and from lunar soils have ages of 4.1-4.4 Ga, more or less the same as the magnesian suite and alkali suite rocks. In the 1960s, NASA researcher John A. O'Keefe and others linked lunar granites with tektites found on Earth although many researchers refuted these claims. According to one study, a portion of lunar sample 12013 has a chemistry that closely resembles javanite tektites found on Earth. Lunar breccias range from glassy vitrophyre melt rocks, to glass-rich breccia, to regolith breccias. The vitrophyres are dominantly glassy rocks that represent impact melt sheets that fill large impact structures. They contain few clasts of the target lithology, which is largely melted by the impact. Glassy breccias form from impact melt that exit the crater and entrain large volumes of crushed (but not melted) ejecta. It may contain abundant clasts that reflect the range of lithologies in the target region, sitting in a matrix of mineral fragments plus glass that welds it all together. Some of the clasts in these breccias are pieces of older breccias, documenting a repeated history of impact brecciation, cooling, and impact. Regolith breccias resemble the glassy breccias but have little or no glass (melt) to weld them together. As noted above, the basin-forming impacts responsible for these breccias pre-date almost all mare basalt volcanism, so clasts of mare basalt are very rare. When found, these clasts represent the earliest phase of mare basalt volcanism preserved.

Mare basalts Mare basalts are named for their frequent rate of constituting a large portion of the lunar maria; they are made of mare basalts, which are like terrestrial basalts but have many important differences. The basalts show a large negative europium anomaly. Extraordinary potassium content can be found in a specific basalt, the so-called VHK (Very High K) basalt.

Stolen and missing moon rocks Because of their rarity, and the difficulty of obtaining more, moon rocks are celebrities amongst stones. They have been targets of vandalism, and many have gone missing or were stolen.

Chapter- 10

Apollo Lunar Surface Experiments Package

ALSEP of the Apollo 16 mission

The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the astronauts at the landing site of each of the five Apollo missions to land on the Moon following Apollo 11 (Apollos 12, 14, 15, 16, and 17). Apollo 11 left a smaller package called the Early Apollo Scientific Experiments Package, or EASEP.

Background The instrumentation and experiments that would comprise ALSEP were decided in February 1966. Specifically, the experiments, institutions responsible, and principal investigators and coinvestigators were:       

Passive Lunar Seismic Experiment: Massachusetts Institute of Technology, Frank Press; Columbia University, George Sutton. Lunar Tri-axis Magnetometer: NASA Ames Research Center, C. P. Sonett; Marshall Space Flight Center, Jerry Modisette. Medium-Energy Solar Wind: Jet Propulsion Laboratory, C. W. Snyder and M. M. Neugebauer. Suprathermal Ion Detection: Rice University, J. W. Freeman, Jr.; Marshall Space Flight Center, Curt Michel. Lunar Heat Flow Management: Columbia University, M. Langseth; Yale University, S. Clark. Low-Energy Solar Wind: Rice University, B. J. O'Brien. Active Lunar Seismic Experiment: Stanford University, R. L. Kovach; United States Geological Survey, J. S. Watkins.

The ALSEP was built and tested by Bendix Aerospace in Ann Arbor, Michigan. The instruments were designed to run autonomously after the astronauts left and to make long term studies of the lunar environment. They were arrayed around a Central Station which supplied power generated by a radioisotope thermoelectric generator (RTG) to run the instruments and communications so data collected by the experiments could be relayed to Earth. Thermal control was achieved by passive elements (insulation, reflectors, thermal coatings) as well as power dissipation resistors and heaters. Data collected from the instruments were converted into a telemetry format and transmitted to Earth.

Deployment The ALSEP was stored in the LM's Scientific Equipment (SEQ) Bay in two separate subpackages. The base of the first subpackage formed the Central Station while the base of the second subpackage was part of the RTG. A subpallet was also attached to the second subpackage which usually carried one or two of the experiments and the antenna gimbal assembly. On Apollo 12, 13, and 14, the second subpackage also stored the Lunar Hand Tool Carrier (HTC). The exact deployment of experiments differed by mission. The following pictures show a typical procedure from Apollo 12.

Picture

Description

Pete Conrad opens the SEQ bay doors through a system of lanyards and pulleys.

Alan Bean removes the second subpackage from the SEQ bay. This was accomplished by using the boom which can be seen extended and a pulley system to set it on the ground. By Apollo 17, astronauts felt that the use of the boom and pulley system complicated the operation. And as such, the entire system was removed for Apollo 17. On Apollo 11, Buzz Aldrin chose not to use the system because of a lack of time.

The first subpackage, which Conrad had removed from the SEQ bay earlier.

Bean lowers the RTG cask into a position where he can access it.

Bean is beginning to remove the dome off the RTG cask. He is using a specialized tool called the Dome Removal Tool (DRT). Note how he has already prepared the RTG for fueling and has already deployed the HTC. Conrad has already removed the subpallet from the RTG subpackage.

Bean discards the dome with the DRT still attached. Neither had a use afterward.

Bean is attempting to remove the fuel element from the cask using the Fuel Transfer Tool (FTT). Note one of the Universal Hand Tools (UHT) attached to the RTG subpackage. On Apollo 12, the fuel element stuck in the cask because of thermal expansion (Bean could feel the heat through his suit). Conrad pounded the side of the cask with a hammer while Bean successfully worked it loose. He then inserted it into the RTG and discarded the FTT.

Bean attaches the RTG subpackage to the carrybar in preparation for the traverse to the ALSEP deployment site. The carrybar would later be used as the mast for the antenna on the Central Station.

During the traverse to the ALSEP deployment site, Conrad took this picture. His shadow indicates that he is carrying the subpallet with one of the two UHTs.

Bean carries the ALSEP out to the deployment site.

Conrad holds the carrybar in his left hand while he releases the antenna gimbal assembly with a UHT.

This photo shows Jim Lovell training for Apollo 13. He is currently deploying a mock-up of the Central Station. The Station was spring loaded. After releasing Boyd bolts, the top of the Station would spring up, deploying it. Note the various locations on top of it which held some of the experiments before deployment. They were also held down with Boyd bolts that were released with a UHT.

Common elements Each ALSEP station had some common elements. Name

Central Station

Diagram

Picture

Description The picture shows the Central Station from Apollo 16's ALSEP. The Central Station was essentially the command center for the entire ALSEP station. It received commands from Earth, transmitted data, and distributed power to each experiment. Communications with Earth were achieved through a 58 cm long, 3.8 cm diameter modified axial-helical antenna mounted on top of the Central Station and pointed towards Earth by the

Radioisotope Thermoelectric Generator (RTG)

RTG Cask

astronauts. Transmitters, receivers, data processors and multiplexers were housed within the Central Station. The Central Station was a 25 kg box with a stowed volume of 34,800 cubic cm. In addition, on Apollos 12 to 15, a Dust Detector was mounted on the Central Station which measured the accumulation of Lunar dust. The picture shows the RTG from Apollo 14 with the Central Station in the background. The RTG was the power source for the ALSEP. It utilized the heat from the radioactive decay of plutonium-238 and thermocouples to generate approximately 70 watts of power. The base of the RTG was the base of the second ALSEP subpackage. The RTG cask stored the plutonium-238 fuel element. It was located to left of the SEQ bay. The cask was designed to withstand a launch vehicle explosion in the event of an abort or a re-entry into Earth's atmosphere (which is what occurred on Apollo 13). The picture shows Edgar Mitchell

practicing the removal of the fuel element.

List of experiments Name

Active Seismic Experiment (ASE)

Diagram

Description Through the use of seismology the internal structure of the Moon could be determined to several hundred feet underground. The ASE consisted of three major components. A set of three geophones was laid out in a line by an astronaut from the Central Station to detect the explosions. A mortar package was designed to lob a set of four explosives from varying distances away from the ALSEP. Finally, an astronaut activated Thumper was used to detonate one of 22 charges to create a small shock. The diagram shows the Thumper device.

Charged Particle Lunar Environment Experiment (CPLEE)

The CPLEE was designed to measure the fluxes of charged particles such as electrons and ions.

Cold Cathode Gauge Experiment (CCGE)

The CCGE was essentially a stand-alone version of the CCIG.

Cold Cathode Ion Gauge (CCIG)

The CCIG experiment was designed to measure the pressure of the Lunar atmosphere. It was originally designed to be part of the SIDE, but its strong magnetic field would have caused interference. The CCIG is on the right of the SIDE in the diagram.

Heat Flow Experiment (HFE)

The HFE was designed to make thermal measurements of the Lunar subsurface in order to determine the rate at which heat flows out of the interior. The measurements could help determine the abundance of radioisotopes and help understand the thermal evolution of the Moon. The HFE consisted of an electronics box and two probes. Each probe was place in a hole by an astronaut that was drilled to about 2.5 m deep.

Laser Ranging Retroreflector (LRRR)

By reflecting a laser shot from Earth off one of LRRRs, the distance to the Moon could be accurately determined. The information could be used to study Lunar recession due to tidal dissipation and the irregular motion of the Earth. The LRRRs are the only experiments still in use today. The above diagram shows the Apollo 11 version. Apollo 14's was similar to Apollo 11's. The lower diagram shows the larger Apollo 15 version.

Lunar Atmosphere Composition Experiment (LACE)

The LACE was designed to detect the composition of the Lunar atmosphere.

Lunar Ejecta and Meteorites Experiment (LEAM)

The LEAM was designed to detect secondary particles that had been ejected by meteorite impacts on the lunar surface and to detect primary micrometeorites themselves.

Lunar Seismic Profiling Experiment (LSPE)

The LSPE was similar to the ASE except the expected depth was to be several kilometers. It consisted of three major components. As set of four geophones was laid out near the ALSEP by an astronaut. The LSPE antenna was used to send signals the charges. There were eight charges each consisting of various sizes ranging from 1/8 to 6 lbs. The charges were deployed during the rover traverses.

Lunar Surface Gravimeter (LSG)

The LSG was designed to make very accurate measurements of lunar gravity and its change over time. It was hoped the data could be used to prove the existence of gravitational waves.

Lunar Surface Magnetometer (LSM)

The LSM was designed to measure the Lunar magnetic field. The data could be used to determine electrical properties of the subsurface. It was also used to study the interaction of solar plasma and the Lunar surface.

Passive Seismic Experiment (PSE)

The PSE was designed to detect "moonquakes," either naturally or artificially created, to help study the structure of the subsurface.

Passive Seismic Experiment Package (PSEP)

Similar to the PSE, except it was selfsupporting. This meant it carried its own power source (solar arrays), electronics, and communications equipment. In addition, the PSEP also carried a Dust Detector.

Solar Wind Spectrometer Experiment (SWS)

The SWS was designed to study solar wind properties and its effects on the Lunar environment.

Suprathermal Ion Detector Experiment (SIDE)

The SIDE was designed to measure various properties of positive ions in the Lunar environment, provide data on the plasma interaction between solar wind and the Moon, and to determine the electrical potential of the Lunar surface.

List of missions Each mission had a different array of experiments.

Apollo 11 (EASEP)

On Apollo 11, Buzz Aldrin simply carried the EASEP to the deployment site by using handles. This is different from the carrybar used on later missions. As stated above, Apollo 11 did not leave a full ALSEP package, but left a simpler version called the Early Apollo Surface Experiments Package (EASEP). Since there was only one 2 hour 40 minute EVA planned, the crew would not have enough time to deploy a full ALSEP, which usually took one to two hours to deploy. Both packages were stored in the LM's SEQ bay.

Name Picture

Notes

LRRR

Notice that the black dust cover has not yet been removed.

PSEP

Failed after 21 days.

Apollo 12

Layout for Apollo 12's ALSEP Name

Picture

Notes

LSM

Stored on the first subpackage.

PSE

Stored on the first subpackage.

SWS

Stored on the first subpackage.

SIDE/CCIG

Stored on the second subpackage as part of the subpallet. The CCIG can be seen to the left of the SIDE. The CCIG failed after only 14 hours.

The antenna gimbal assembly was stored on the subpallet. The stool for the PSE, the ALSEP tools, carrybar, and HTC was stored on the second subpackage.

Apollo 13

Planned layout for Apollo 13's ALSEP

A recording of the Apollo 13 S-IVB's impact on the lunar surface as detected by the Apollo 12 Passive Seismic Experiment. Because of the aborted landing, none of the experiments were deployed. However, the Apollo 13 S-IVB stage was deliberately crashed on the Moon to provide a signal for the Apollo 12 PSE. Name Notes CPLEE Stored on the first subpackage. Stored on the first subpackage. CCGE Only time the CCGE was flown. Stored on the first subpackage. HFE Stored on the first subpackage. PSE The antenna gimbal assembly was stored on the first subpackage. The stool for the PSE, the ALSEP tools, carrybar, and the Lunar drill was stored on the subpallet. The HTC was stored on the second subpackage.

Apollo 14

Layout for Apollo 14's ALSEP Name

ASE

Picture

Notes

The above image shows the mortar package. The lower one shows Lunar Module Pilot Edgar Mitchell operating the Thumper. The mortar package, geophones, and Thumper was stored on the first subpackage. Thirteen of the twenty-two Thumper charges were fired successfully. Because of concerns about the deployment of the mortar package, none of the four explosives were fired. There was an attempt to fire them at the end of the ALSEP's operational lifetime, but the charges failed to work after being dormant for so long.

CPLEE

Stored on the first subpackage.

LRRR

Stored in Quad I of the LM and brought to the ALSEP site separately.

PSE

Stored on the first subpackage.

SIDE/CCIG

Stored on the subpallet. The SIDE is in the upper-left corner while the CCIG is in the center of the picture.

The antenna gimbal assembly was stored on the subpallet. The stool for the PSE, the ALSEP tools, carrybar, and HTC was stored on the second subpackage.

Apollo 15

Layout of Apollo 15's ALSEP Name

HFE

Picture

Notes The center of the picture shows the electronics box and the two wires going to each of the probes. Stored on the second subpackage. During the drilling operations for each of the holes, more resistance was encountered than expected. As a result, the probes could not be inserted to their planned depth. Accurate scientific data could not be obtained from the Apollo 15 experiment until the data could be compared to Apollo 17's.

LRRR

Stored in Quad III of the LM and brought to the ALSEP site via the Lunar rover.

LSM

Stored on the first subpackage.

PSE

Stored on the first subpackage.

SWS

Stored on the first subpackage.

SIDE/CCIG

The SIDE is on the left while the CCIG is attached on the right. Stored on the subpallet. Note the tilt of the SIDE. This was necessary because of the latitude of Apollo 15's landing site. Also note the boom connecting the SIDE and CCIG. This redesign was done because earlier crews complained about the difficulty to deploy the SIDE/CCIG when only wires connected the two experiments.

The antenna gimbal assembly was stored on the subpallet. The ALSEP tools, carrybar, and stool for the PSE was stored on the second subpackage.

Apollo 16

Layout for Apollo 16's ALSEP Name Picture Notes The picture shows the mortar package. Note the new base used to improve the experiment after problems were encountered with Apollo 14's. The mortar package, geophones, and Thumper was stored on the first subpackage. The base of the mortar box was stored on the second ASE subpackage. After three of the explosives were fired successfully, the pitch sensor went off scale. It was then decided not to fire the fourth explosive. Nineteen of the Thumper charges were successfully fired. The picture shows the one heat flow probe that was successfully deployed. Stored on the second subpackage. After successfully deploying one of the probes, Commander John Young HFE inadvertently caught his foot on the cable to the experiment from the Central Station. The cable was pulled out of its connector on the Central Station. It could not be repaired and the experiment was terminated. LSM

Stored on the first subpackage.

PSE

Stored on the first subpackage.

Apollo 17

Layout of Apollo 17's ALSEP Name Picture HFE

LACE

Notes One of the probes can be seen in the foreground while the electronics box and the other probe can be seen in the background.

LEAM

The LEAM is in the foreground. The scientific validity of this experiment has been called into question because of some odd data.

LSPE

The upper image shows the antenna for the LSPE in the foreground. The lower image shows one of the charges.

LSG

Because of a design error, the experiment could not accomplish what it was designed for.

After Apollo

LRO photo showing Apollo 12 ALSEP The ALSEP system and instruments were controlled by commands from Earth. The stations ran from deployment until they were turned off on 30 September 1977 due primarily to budgetary considerations. Additionally, by 1977 the power packs could not run both the transmitter and any other instrument, and the ALSEP control room was needed for the attempt to reactivate Skylab. ALSEP systems are visible in several images taken by the Lunar Reconnaissance Orbiter during its orbits over Apollo landing sites.