Shoemaker is a

lunar Lunar most commonly means "of or relating to the Moon". Lunar may also refer to: Arts and entertainment * ''Lunar'' (series), a series of video games * "Lunar" (song), by David Guetta * "Lunar", a song by Priestess from the 2009 album ''Prior t ...

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

located near the southern pole of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

, within half a crater diameter of Shackleton.

Crater

It lies to the south of the crater Malapert, to the east of

Haworth Haworth ( , , ) is a village in West Yorkshire, England, in the Pennines south-west of Keighley, 8 miles (13 km) north of Halifax, west of Bradford and east of Colne in Lancashire. The surrounding areas include Oakworth and Oxenhop ...

, 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 (it is a

crater of eternal darkness A permanently shadowed crater is a depression on a body in the Solar System within which lies a point that is always in darkness. As of 2019, there are 324 known permanently shadowed regions on the Moon. Such regions also exist on Mercury (plane ...

), the

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

of the interior floor surface remains unknown. Prior to being given its current name by the

IAU The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

, this formation had been informally named Mawson (after the

Antarctic The Antarctic (, ; commonly ) is the polar regions of Earth, polar region of Earth that surrounds the South Pole, lying within the Antarctic Circle. It is antipodes, diametrically opposite of the Arctic region around the North Pole. The Antar ...

explorer

Douglas Mawson Sir Douglas Mawson (5 May 1882 – 14 October 1958) was a British-born Australian geologist, Antarctic explorer, and academic. Along with Roald Amundsen, Robert Falcon Scott, and Sir Ernest Shackleton, he was a key expedition leader during ...

). It was officially named Shoemaker in honor of

Eugene Shoemaker Eugene Merle Shoemaker (April 28, 1928 – July 18, 1997) was an American geologist. He co-discovered Comet Shoemaker–Levy 9 with his wife Carolyn S. Shoemaker and David H. Levy. This comet hit Jupiter in July 1994: the impact was telev ...

, the

geologist A geologist is a scientist who studies the structure, composition, and History of Earth, history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the Field research, ...

whose remains were on board the

Lunar Prospector ''Lunar Prospector'' was a spacecraft that orbited the Moon for 19 months in 1998-99. From a low polar orbit, it mapped surface composition including lunar hydrogen deposits, measured magnetic and gravity fields, and studied lunar outgassing e ...

spacecraft that impacted this crater floor. Deposition of Shoemaker's remains was criticized by

indigenous peoples There is no generally accepted definition of Indigenous peoples, although in the 21st century the focus has been on self-identification, cultural difference from other groups in a state, a special relationship with their traditional territ ...

as a desecration of the venerated Moon.

Cold trap deposits

This crater became of interest to scientists when the Lunar Prospector detected unusually high concentrations of

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

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 The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, and thus maintains a temperature below . Thus the floor forms a cold trap, and any molecules of water that wander into the crater from

comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...

ary impacts can deposit on the floor and remain there 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 m antenna to irradiate it with 3.5 cm

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

. Two 34 m antennae, located 20 km apart, received the echoes, and the results were used to generate a

topographic map In modern mapping, a topographic map or topographic sheet is a type of map characterized by large- scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but histori ...

with 150 m resolution. 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.

Crater

Cold trap deposits

References

General references

External links