Chao Meng-Fu (crater)
Encyclopedia
Chao Meng-Fu is a 167 kilometer-diameter crater
on Mercury
named after the Chinese
painter and calligrapher Zhao Mengfu
(1254 - 1322). Due to its location near Mercury's south pole (132.4° west, 87.3° south) and the planet's small axial tilt
, an estimated 40% of the crater lies in permanent shadow. This combined with bright radar echoes from the location of the crater leads scientists to suspect that it may shelter large quantities of ice
protected against sublimation into the near-vacuum by the constant -171°C temperatures.
studies involving Arecibo
(Puerto Rico
), Goldstone
(California
, United States
), and the Very Large Array
(New Mexico
, United States
) detected a number of highly-radar-reflective depolarized areas on Mercury, including several locations at the planet's poles
. Many of these reflective features appear to coincide with craters imaged by Mariner 10
, with the largest feature at the south pole corresponding to Chao Meng-Fu crater.
The luminosity and depolarization of the radar reflections are much more characteristic of ice than of the silicate
rocks making up Mercury's crust
. Still, these reflections are too dim to be pure ice; it has been hypothesized that this is due to a thin or partial layer of powder over the underlying ice. However, with no direct confirmation, it is always possible that the observed radar reflectivity from Chao Meng-Fu and similar craters is due to depositions of metal
-rich minerals and compounds. NASA
's MESSENGER
mission may provide additional evidence for or against the presence of ice when it begins orbiting Mercury in 2011.
. Due to bombardment by the solar wind
and intense light from the Sun, ice deposits on most of Mercury would be rapidly lost to space; in the permanently shadowed portions of Chao Meng-Fu, though, temperatures are too low to permit appreciable sublimation and ice may well have accumulated over billions of years.
's Vacuum Diagrams
.
Gerald Nordley
's short story "Crossing Chao Meng-Fu" depicts rock-climbers struggling to traverse the crater.
Mark Anson's novel Below Mercury is set in an abandoned ice mine below Chao Meng-fu 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...
on Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
named after the Chinese
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
painter and calligrapher Zhao Mengfu
Zhao Mengfu
Zhao Mengfu courtesy name Ziang , pseudonyms Songxue , Oubo , and Shuijing-gong Dao-ren , was a prince and descendant of the Song Dynasty, and a Chinese scholar, painter and calligrapher during the Yuan Dynasty.He was recommended by the Censor-in-chief Cheng Jufu to pay an audience...
(1254 - 1322). Due to its location near Mercury's south pole (132.4° west, 87.3° south) and the planet's small axial tilt
Axial tilt
In astronomy, axial tilt is the angle between an object's rotational axis, and a line perpendicular to its orbital plane...
, an estimated 40% of the crater lies in permanent shadow. This combined with bright radar echoes from the location of the crater leads scientists to suspect that it may shelter large quantities of ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
protected against sublimation into the near-vacuum by the constant -171°C temperatures.
Radar evidence for ice
RadarRadar
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...
studies involving Arecibo
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
(Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
), 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...
(California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
), and the Very Large Array
Very Large Array
The Very Large Array is a radio astronomy observatory located on the Plains of San Agustin, between the towns of Magdalena and Datil, some fifty miles west of Socorro, New Mexico, USA...
(New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
) detected a number of highly-radar-reflective depolarized areas on Mercury, including several locations at the planet's poles
Geographical pole
A geographical pole is either of the two points—the north pole and the south pole—on the surface of a rotating planet where the axis of rotation meets the surface of the body...
. Many of these reflective features appear to coincide with craters imaged by Mariner 10
Mariner 10
Mariner 10 was an American robotic space probe launched by NASA on November 3, 1973, to fly by the planets Mercury and Venus. It was launched approximately two years after Mariner 9 and was the last spacecraft in the Mariner program...
, with the largest feature at the south pole corresponding to Chao Meng-Fu crater.
The luminosity and depolarization of the radar reflections are much more characteristic of ice than of the silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
rocks making up Mercury's crust
Crust
Crust may refer to:* Crust * The Crust, television seriesPhysical sciences:* Crust , at least continent-wide structure* Soil crust, local biology-sensitive structureFood:* Crust, dense surface layer of bread...
. Still, these reflections are too dim to be pure ice; it has been hypothesized that this is due to a thin or partial layer of powder over the underlying ice. However, with no direct confirmation, it is always possible that the observed radar reflectivity from Chao Meng-Fu and similar craters is due to depositions of metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
-rich minerals and compounds. NASA
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...
's MESSENGER
MESSENGER
The MErcury Surface, Space ENvironment, GEochemistry and Ranging space probe is a robotic NASA spacecraft in orbit around the planet Mercury. The spacecraft was launched aboard a Delta II rocket in August 2004 to study the chemical composition, geology, and magnetic field of Mercury...
mission may provide additional evidence for or against the presence of ice when it begins orbiting Mercury in 2011.
Ice origins
Chao Meng-Fu's ice may have originated from impacts of water-rich meteorites and comets or from internal outgassingOutgassing
Outgassing is the release of a gas that was dissolved, trapped, frozen or absorbed in some material. As an example, research has shown how the concentration of carbon dioxide in the Earth's atmosphere has sometimes been linked to ocean outgassing...
. Due to bombardment by 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...
and intense light from the Sun, ice deposits on most of Mercury would be rapidly lost to space; in the permanently shadowed portions of Chao Meng-Fu, though, temperatures are too low to permit appreciable sublimation and ice may well have accumulated over billions of years.
Chao Meng-Fu crater in fiction
A geothermally heated ocean beneath Chao Meng-Fu crater serves as the home of an alien species in Stephen BaxterStephen Baxter
Stephen Baxter is a prolific British hard science fiction author. He has degrees in mathematics and engineering.- Writing style :...
's Vacuum Diagrams
Vacuum Diagrams
Vacuum Diagrams is a collection of science fiction short stories written by Stephen Baxter. The collection connects the novels of the Xeelee Sequence and also shows the history of mankind in the Xeelee universe, and ultimately the universe...
.
Gerald Nordley
G. David Nordley
G. David Nordley is a science fiction writer and physicist whose fiction writing is most associated with Analog Science Fiction and Fact. His fiction is under the name G. David Nordley while his technical writing is written under the name Gerald D. Nordley...
's short story "Crossing Chao Meng-Fu" depicts rock-climbers struggling to traverse the crater.
Mark Anson's novel Below Mercury is set in an abandoned ice mine below Chao Meng-fu crater.
See also
- Geology of MercuryGeology of MercuryThe surface of Mercury is dominated by impact craters, and lava plains similar in some respects to the lunar maria. Other notable features include scarps and mineral deposits inside craters at the poles. Currently, the surface is presumed to be geologically inactive...
- List of craters on Mercury
- List of geological features on Mercury
External links
- Radar Imaging of Mercury's North and South Poles at 3.5 cm Wavelength contains radar images, including one showing the bright reflection from Chao Meng-Fu crater.