Shoemaker (lunar crater)
Encyclopedia
Shoemaker is a lunar
crater
that is located near the southern pole
of the Moon
, within half a crater diameter of Shackleton
. It lies to the south of the crater Malapert
, to the east of Haworth
, and just to the west of the similar-sized Faustini
. The rim of Shoemaker is circular and worn, with some small craters along the inner wall. Due to the lack of illumination, the albedo
of the interior floor surface remains unknown.
Prior to being given its current name by the IAU
, this formation had been informally named Mawson (after the Antarctic
explorer Douglas Mawson
). It was officially named Shoemaker in honor of Eugene Shoemaker, the geologist
whose remains were on board the Lunar Prospector
spacecraft that impacted this crater floor.
on the floor of this and other nearby craters using a neutron
spectrometer
. The floor of this crater is kept in permanent shadow from the Sun
, and thus maintains a temperature below 100 K
. Thus the floor forms a cold trap, and any molecules of water that wander into the crater from comet
ary impacts can deposit on the floor and remain here almost permanently. The instruments on board Lunar Prospector gave a concentration of about 146 ppm of hydrogen, compared to 50 ppm for the average lunar surface.
The topography of this crater was subsequently measured using the Goldstone
70-meter antenna
to irradiate it with 3.5 cm radar
. Two 34-meter antennae, located 20 kilometers apart, received the echoes, and the results were used to generate a coarse topographic map
.
On July 31, 1999, Lunar Prospector was deliberately crashed into the floor of this crater to determine if a plume of water vapor would be detected. The apparent detection of water and the shallow rim of this crater made it a suitable target for this experiment. However the outcome was unsuccessful. Subsequent tests have failed to confirm the presence of water in the crater floor, so the hydrogen found in the crater bottom is likely to prove more difficult to extract than had been originally hoped.
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
that is located near the southern pole
Lunar south pole
The lunar south pole is of special interest to scientists because of the postulated occurrence of ice in permanently shadowed areas. Of the lunar poles, the south pole is of greater interest because the area that remains in shadow is much larger than that at the north pole. The lunar south pole...
of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, within half a crater diameter of Shackleton
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. The low-temperature interior of this crater functions as a cold trap that may capture and freeze volatiles...
. It lies to the south of the crater Malapert
Malapert (crater)
Malapert is a lunar crater that lies near the southern limb of the Moon. From the Earth this formation is viewed from the side, limiting the amount of detail that can be seen. The crater is also illuminated at very low angles, so that parts of the interior remain in almost constant darkness...
, to the east of Haworth
Haworth (crater)
Haworth is an impact crater that lies at the south pole of the Moon. The crater is named after Walter Haworth.-Description:The crater was imaged by Diviner. Cabeus Crater is nearby.-External links:*...
, and just to the west of the similar-sized Faustini
Faustini (crater)
Faustini is a lunar crater that lies near the south pole of the Moon. It is located nearly due south of the much larger crater Amundsen, and is almost attached to Shoemaker to the southwest. About one crater diameter due south is the smaller crater Shackleton at the south pole...
. The rim of Shoemaker is circular and worn, with some small craters along the inner wall. Due to the lack of illumination, the albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
of the interior floor surface remains unknown.
Prior to being given its current name by the IAU
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
, this formation had been informally named Mawson (after the Antarctic
Antarctic
The Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...
explorer Douglas Mawson
Douglas Mawson
Sir Douglas Mawson, OBE, FRS, FAA was an Australian geologist, Antarctic explorer and Academic. Along with Roald Amundsen, Robert Falcon Scott, and Ernest Shackleton, Mawson was a key expedition leader during the Heroic Age of Antarctic Exploration.-Early work:He was appointed geologist to an...
). It was officially named Shoemaker in honor of Eugene Shoemaker, the geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...
whose remains were on board the Lunar Prospector
Lunar Prospector
The Lunar Prospector mission was the third selected by NASA for full development and construction as part of the Discovery Program. At a cost of $62.8 million, the 19-month mission was designed for a low polar orbit investigation of the Moon, including mapping of surface composition and possible...
spacecraft that impacted this crater floor.
Cold trap deposits
This crater became of interest to scientists when the Lunar Prospector detected unusually high concentrations of hydrogenHydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
on the floor of this and other nearby craters using a neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
spectrometer
Spectrometer
A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
. The floor of this crater is kept in permanent shadow from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, and thus maintains a temperature below 100 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
. Thus the floor forms a cold trap, and any molecules of water that wander into the crater from comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
ary impacts can deposit on the floor and remain here almost permanently. The instruments on board Lunar Prospector gave a concentration of about 146 ppm of hydrogen, compared to 50 ppm for the average lunar surface.
The topography of this crater was subsequently measured using the Goldstone
Goldstone Deep Space Communications Complex
The Goldstone Deep Space Communications Complex — commonly called the Goldstone Observatory — is located in California's Mojave Desert. Operated by ITT Corporation for the Jet Propulsion Laboratory, its main purpose is to track and communicate with space missions. It includes the Pioneer...
70-meter antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
to irradiate it with 3.5 cm radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
. Two 34-meter antennae, located 20 kilometers apart, received the echoes, and the results were used to generate a coarse topographic map
Topographic map
A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines in modern mapping, but historically using a variety of methods. Traditional definitions require a topographic map to show both natural and man-made features...
.
On July 31, 1999, Lunar Prospector was deliberately crashed into the floor of this crater to determine if a plume of water vapor would be detected. The apparent detection of water and the shallow rim of this crater made it a suitable target for this experiment. However the outcome was unsuccessful. Subsequent tests have failed to confirm the presence of water in the crater floor, so the hydrogen found in the crater bottom is likely to prove more difficult to extract than had been originally hoped.