Illumination map of Mercury's south pole Chabot Fig2

Permanent shadows at Mercury's south pole Chabot Fig3

Chao Meng-Fu is a diameter crater on Mercury named after the Chinese painter and calligrapher

Zhao Mengfu Zhao Mengfu (; courtesy name Zi'ang (子昂); pseudonyms Songxue (松雪, "Pine Snow"), Oubo (鷗波, "Gull Waves"), and Shuijing-gong Dao-ren (水精宮道人, "Master of the Water Spirits Palace"); 1254–1322), was a Chinese calligrapher, pa ...

(1254–1322). Due to its location near Mercury's south pole (132.4° west, 87.3° south) and the planet's small

axial tilt In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orb ...

, 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 is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...

protected against

sublimation Sublimation or sublimate may refer to: * ''Sublimation'' (album), by Canvas Solaris, 2004 * Sublimation (phase transition), directly from the solid to the gas phase * Sublimation (psychology), a mature type of defense mechanism * Sublimate of mer ...

into the near-vacuum by the constant temperatures.

Radar evidence for ice

Radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

studies involving

Arecibo Arecibo (; ) is a city and municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado and Ciales; east of Hatillo; and west of Barceloneta and Florida. It is about west of San Juan, the c ...

(

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...

), Goldstone (

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

), and the

Very Large Array The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~ west of Socorro. The VLA comprises twent ...

(

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...

) 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 ''Mariner 10'' was an American robotic space probe launched by NASA on 3 November 1973, to fly by the planets Mercury and Venus. It was the first spacecraft to perform flybys of multiple planets. ''Mariner 10'' was launched approximately ...

'', 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 A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typi ...

-rich minerals and compounds.

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedi ...

's ''

MESSENGER ''MESSENGER'' was a NASA robotic space probe that orbited the planet Mercury between 2011 and 2015, studying Mercury's chemical composition, geology, and magnetic field. The name is a backronym for "Mercury Surface, Space Environment, Geoch ...

'' mission confirmed the strong correlation of radar reflectivity with permanently shadowed craters, as shown on the maps to the right.

Ice origins

Chao Meng-Fu's ice may have originated from impacts of water-rich

meteorites A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object e ...

and

comets A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...

or from internal

outgassing Outgassing (sometimes called offgassing, particularly when in reference to indoor air quality) is the release of a gas that was dissolved, trapped, frozen, or absorbed in some material. Outgassing can include sublimation and evaporation (which ...

. Due to bombardment by the

solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the ...

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

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 Baxter's story ''Cilia-of-Gold,'' first published in the August 1994 issue of

Asimov's ''Asimov's Science Fiction'' is an American science fiction magazine which publishes science fiction and fantasy named after science fiction author Isaac Asimov. It is currently published by Penny Publications. From January 2017, the publication ...

and reprinted in his collection Vacuum Diagrams. Gerald Nordley's novelette ''Crossing Chao Meng-Fu,'' originally published in the December 1997 issue of

Analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analo ...

, depicts rock-climbers struggling to traverse the crater. Mark Anson's novel ''Below Mercury''Anson, Mark. ''Below Mercury''. Glenn Field Publishing, 2011. is set in an abandoned ice mine below Chao Meng-fu crater.

References

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. {{Mercury (planet) Impact craters on Mercury

Radar evidence for ice

Ice origins

Chao Meng-Fu crater in fiction

See also

References

External links