 = Shackleton ( crater ) = 
 
 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 ( a Crater of eternal darkness ) . 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 Antarctic explorer Ernest Shackleton . 
 
 = = 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 , it is viewed edge @-@ on 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 . Estimates of the area in permanent shadow were obtained from Earth @-@ based radar studies . 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 = = 
 
 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 Earth @-@ based radar and spacecraft images of the crater edge , 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 . ( See Shoemaker ( lunar crater ) , for example . ) 
 Radar studies preceding and 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 = = 
 
 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 . 
 
 