Cabeus (crater)
Encyclopedia
Cabeus is a lunar
crater
that is located about 100 km (62.1 mi) from the south pole
of the Moon
. At this location the crater is seen obliquely from Earth
, and it is almost perpetually in deep shadow due to lack of sunlight
. Hence, not much detail can be seen of this crater, even from orbit. Through a telescope
, this crater appears near the southern limb of the Moon, to the west of the crater Malapert
and to the south-southwest of Newton
.
. The official name and location for this crater was adopted by the IAU
Commission 17, as established in the 1935 work Named Lunar Formations by Mary A. Blagg
and Karl Müller.
This crater is a worn formation that has been eroded by subsequent impacts. The rim is eroded and uneven, with prominent ridges at the northern and southern ends. A small crater lies across the northeastern rim and there is 10–11 km crater on the interior floor near the west-southwestern rim. Near the center of the crater floor is a small ridge. The floor of the crater has an average depth of 4 km and it is 60 km across. The slope of the crater walls is 10–15°.
Because of the crater's location near the lunar south pole, the main part of the crater is illuminated by the Sun during only 25% of each lunar day. The inner walls receive illumination for 30% of a lunar day, while part of the western end of the crater is in permanent shadow.
spacecraft and a hydrogen signature was detected. Potential sources for this hydrogen include water deposits from comet or meteorite impacts, the solar wind
or out-gassing. This crater is sufficiently large that the temperature within the shaded region is below 100 K (-173.2 °C). This would allow water ice to remain on or near the crater surface for billions of years without sublimating.
National Aeronautics and Space Administration
launched the LCROSS
, impactor spacecraft on 18 June 2009, to look for water
at the Lunar south pole
. On 28 September 2009, Cabeus proper was selected as the impact target for the LCROSS
mission, switching the target from satellite crater Cabeus A. The change was made after review of the latest data gathered by other lunar exploration craft, which indicated that Cabeus proper had a higher concentration of hydrogen than Cabeus A.
At 11:31 UTC on 9 October 2009 the Centaur
upper stage of its Atlas V
carrier rocket impacted Cabeus, followed shortly thereafter by the impact of the LCROSS spacecraft itself. The impact of the Centaur was intended to throw up a plume of lunar surface material to be sampled by sensors carried on the LCROSS spacecraft as it traversed the plume. But the debris plumes were smaller than predicted. Preliminary data from the LCROSS spectrometer measurements of the impact plume appeared to confirm the presence of water in the crater.
Analysis of the plume observations supports the presence of water in the regolith. Absorption in the near-infrared can be attributed to ice and water vapor, while emissions in the ultraviolet indicate the presence of hydroxyl radicals, which also supports the likelihood of water. The estimated total amount of water vapor and ice in the plume is up to , or an estimated by mass. The spectral signatures of other volatiles were observed, matching the signatures of carbon dioxide
, light hydrocarbon
s, and sulfur
-bearing compounds.
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 about 100 km (62.1 mi) from the south 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...
. At this location the crater is seen obliquely from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, and it is almost perpetually in deep shadow due to lack of sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
. Hence, not much detail can be seen of this crater, even from orbit. Through a telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
, this crater appears near the southern limb of the Moon, to the west 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...
and to the south-southwest of Newton
Newton (lunar crater)
Newton is a lunar crater located near the south limb of the Moon. It is south-southwest of the crater Moretus. To the northeast is Short, and in the northeast are Casatus and Klaproth. Because of its location, the crater appears highly oblong due to foreshortening. It is considered the deepest...
.
Description
The crater name Cabeus first appeared in the 1651 work Almagestum Novum by Giovanni Riccioli. However, the position of the Cabeus crater was in the location later assigned to Newton craterNewton (lunar crater)
Newton is a lunar crater located near the south limb of the Moon. It is south-southwest of the crater Moretus. To the northeast is Short, and in the northeast are Casatus and Klaproth. Because of its location, the crater appears highly oblong due to foreshortening. It is considered the deepest...
. The official name and location for this crater was adopted 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...
Commission 17, as established in the 1935 work Named Lunar Formations by Mary A. Blagg
Mary Adela Blagg
Mary Adela Blagg was an English astronomer.She was born in Cheadle, Staffordshire, and lived her entire life there. Mary was the daughter of a solicitor, John Charles Blagg, and France Caroline Foottit. She trained herself in mathematics by reading her brother's textbooks...
and Karl Müller.
This crater is a worn formation that has been eroded by subsequent impacts. The rim is eroded and uneven, with prominent ridges at the northern and southern ends. A small crater lies across the northeastern rim and there is 10–11 km crater on the interior floor near the west-southwestern rim. Near the center of the crater floor is a small ridge. The floor of the crater has an average depth of 4 km and it is 60 km across. The slope of the crater walls is 10–15°.
Because of the crater's location near the lunar south pole, the main part of the crater is illuminated by the Sun during only 25% of each lunar day. The inner walls receive illumination for 30% of a lunar day, while part of the western end of the crater is in permanent shadow.
Volatiles
The south polar region of the Moon was surveyed by the Lunar ProspectorLunar 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 and a hydrogen signature was detected. Potential sources for this hydrogen include water deposits from comet or meteorite impacts, the solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
or out-gassing. This crater is sufficiently large that the temperature within the shaded region is below 100 K (-173.2 °C). This would allow water ice to remain on or near the crater surface for billions of years without sublimating.
LCROSS
The United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
National Aeronautics and Space Administration
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
launched the LCROSS
LCROSS
The Lunar Crater Observation and Sensing Satellite was a robotic spacecraft operated by NASA. The mission was conceived as a low-cost means of determining the nature of hydrogen detected at the polar regions of the moon. The main LCROSS mission objective was to explore the presence of water ice...
, impactor spacecraft on 18 June 2009, to look for water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
at the Lunar south 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...
. On 28 September 2009, Cabeus proper was selected as the impact target for the LCROSS
LCROSS
The Lunar Crater Observation and Sensing Satellite was a robotic spacecraft operated by NASA. The mission was conceived as a low-cost means of determining the nature of hydrogen detected at the polar regions of the moon. The main LCROSS mission objective was to explore the presence of water ice...
mission, switching the target from satellite crater Cabeus A. The change was made after review of the latest data gathered by other lunar exploration craft, which indicated that Cabeus proper had a higher concentration of hydrogen than Cabeus A.
At 11:31 UTC on 9 October 2009 the Centaur
Centaur (rocket stage)
Centaur is a rocket stage designed for use as the upper stage of space launch vehicles. Centaur boosts its satellite payload to geosynchronous orbit or, in the case of an interplanetary space probe, to or near to escape velocity...
upper stage of its Atlas V
Atlas V
Atlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance...
carrier rocket impacted Cabeus, followed shortly thereafter by the impact of the LCROSS spacecraft itself. The impact of the Centaur was intended to throw up a plume of lunar surface material to be sampled by sensors carried on the LCROSS spacecraft as it traversed the plume. But the debris plumes were smaller than predicted. Preliminary data from the LCROSS spectrometer measurements of the impact plume appeared to confirm the presence of water in the crater.
Analysis of the plume observations supports the presence of water in the regolith. Absorption in the near-infrared can be attributed to ice and water vapor, while emissions in the ultraviolet indicate the presence of hydroxyl radicals, which also supports the likelihood of water. The estimated total amount of water vapor and ice in the plume is up to , or an estimated by mass. The spectral signatures of other volatiles were observed, matching the signatures of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, light hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
s, and sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
-bearing compounds.
Satellite craters
By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Cabeus.| Cabeus | Latitude | Longitude | Diameter |
|---|---|---|---|
| A | 82.2° S | 39.1° W | 48 km |
| B | 82.4° S | 53.0° W | 61 km |