planetary nomenclature Planetary nomenclature, like terrestrial nomenclature, is a system of uniquely identifying features on the surface of a planet or natural satellite so that the features can be easily located, described, and discussed. Since the invention of the ...

, a chasma (''plural'': chasmata ) is a deep, elongated, steep-sided depression. As of 2020, 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 ...

has named 122 such features in the Solar System, on

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

(63),

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

(25), Saturn's satellites Mimas (6), Tethys (2), Dione (8) and Rhea (5), Uranus's satellites Ariel (7), Titania (2) and

Oberon Oberon () is a king of the fairy, fairies in Middle Ages, medieval and Renaissance literature. He is best known as a character in William Shakespeare's play ''A Midsummer Night's Dream'', in which he is King of the Fairies and spouse of Titania ...

(1) and Pluto's satellite

Charon In Greek mythology, Charon or Kharon ( ; ) is a psychopomp, the ferryman of the Greek underworld. He carries the souls of those who have been given funeral rites across the rivers Acheron and Styx, which separate the worlds of the living and ...

(3). An example is Eos Chasma on

Mars

Below are images of some of the major chasmata of Mars. The map shows their relative locations.

Interior layered deposits and sulfate

Parts of the floor of Candor Chasma contains layered deposits that have been termed interior layered deposits (ILD's). These layers may have formed when the whole area was a giant lake. Some places on Mars contain hydrated

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

deposits. Sulfate formation involves the presence of water. The

European Space Agency The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...

Mars Express ''Mars Express'' is a space exploration mission by the European Space Agency, European Space Agency (ESA) exploring the planet Mars and its moons since 2003, and the first planetary mission attempted by ESA. ''Mars Express'' consisted of two ...

found evidence of perhaps

epsomite Epsomite, Epsom salt, or magnesium sulfate heptahydrate, is a hydrous magnesium sulfate mineral with formula . Physical properties Epsomite crystallizes in the orthorhombic system. The normal form is as massive encrustations, while acicula ...

and

kieserite Kieserite, or magnesium sulfate monohydrate, is a hydrous magnesium sulfate mineral with formula (MgSO4·H2O). It has a vitreous luster and it is colorless, grayish-white or yellowish. Its hardness is 3.5 and crystallizes in the monoclinic crys ...

. Scientists want to visit these areas with robotic rovers.

Layers

Images of rocks in the canyon walls almost always show layers. Some layers appear tougher than others. In the image below of Ganges Chasma Layers, as seen by

HiRISE High Resolution Imaging Science Experiment is a camera on board the '' Mars Reconnaissance Orbiter'' which has been orbiting and studying Mars since 2006. The 65 kg (143 lb), US$40 million instrument was built under the direction ...

, one can see that the upper, light-toned deposits are eroding much faster than the lower darker layers. Some cliffs on Mars show a few darker layers standing out and often breaking into large pieces; these are thought to be hard volcanic rock instead of soft ash deposits. An example of hard layers is shown below in the picture of layers in the canyon wall in Coprates, as seen by

Mars Global Surveyor ''Mars Global Surveyor'' (MGS) was an American Robotic spacecraft, robotic space probe developed by NASA's Jet Propulsion Laboratory. It launched November 1996 and collected data from 1997 to 2006. MGS was a global mapping mission that examined ...

. Because of its closeness to the Tharsis volcanic region, the rock layers may be made of layer after layer of

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

flows, probably mixed with deposits of volcanic ash that fell out of the air following big eruptions. It is likely the rock strata in the walls preserve a long geological history of Mars. Dark layers may be due to dark lava flows. The dark volcanic rock

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

is common on Mars. However, light-toned deposits may have resulted from rivers, lakes, volcanic ash, or wind blown deposits of sand or dust. The

Mars Rovers A Mars rover is a remote-controlled motor vehicle designed to travel on the surface of Mars. Rover (space exploration), Rovers have several advantages over stationary Lander (spacecraft), landers: they examine more territory, they can be directe ...

found light-toned rocks to contain

sulfates The sulfate or sulphate ion is a Polyatomic ion, polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salt (chemistry), ...

. Probably having been formed in water, sulfate deposits are of great interest to scientists because they may contain traces of ancient life.

Hebes Chasma and hydrated deposits

Hebes Chasma, a large enclosed valley, may have once held water. Hydrated minerals have been found there. It is thought that large-scale underground springs of groundwater at different times burst to the surface to form deposits called Light Toned Deposits (LTD's). Some suggest present or fossilized life forms may be found there because the deposits are relatively young.http://www.universetoday.com/2008/12/11/Groundwater May Have Played Important Role in Shaping Mars Image:Coprates map.JPG, Map of Coprates quadrangle showing details of

Valles Marineris Valles Marineris (; Latin for ''Mariner program, Mariner Valleys'', named after the Mariner 9 Mars orbiter of 1971–72 which discovered it) is a system of canyons that runs along the Mars, Martian surface east of the Tharsis region. At more than ...

, the largest canyon system in the solar system. Some of the canyons may have once been filled with water. The map shows the locations of a number of major Chasma. Image:Candor Chasm in Coprates.JPG, False color image of

Candor Chasma Candor Chasma is one of the largest canyons in the Valles Marineris canyon system on Mars. The feature is geographically divided into two halves: East and West Candor Chasmas, respectively. It is unclear how the canyon originally formed; one the ...

showing locations of hydrated

deposits, as seen by

THEMIS In Greek mythology and religion, Themis (; ) is the goddess and personification of justice, divine order, law, and custom. She is one of the twelve Titan children of Gaia and Uranus, and the second wife of Zeus. She is associated with oracles a ...

. Red colors show rocky places. Greens and blues show sandy, dusty areas. Image:Melas Chasma.JPG, Melas Chasma, as seen by

. Click on image to see relationship of Melas to other features. Image:Cliff in Candor Chasma.JPG, Cliff in

Plateau, as seen by

. Click on image to see relationship with other features in Coprates quadrangle. Image:Ganges Chasma.JPG, Cliff in northern wall of Ganges Chasma, as seen by

. Click on image to see relationship with other features in the Coprates quadrangle. Image:Ophir Chasma Wall.JPG,

Ophir Chasma Ophir Chasma is a canyon in the Coprates quadrangle of Mars at 4° south latitude and 72.5° west longitude. It is about 317 km long and was named after Ophir, a land mentioned in the Bible. In the Bible it was the land which King Solo ...

Wall, as seen by

. Image:Ius Chasma.JPG, Ius Chasma, as seen by

. Click on image to see layers. Image:Tithonium Chasma Layers.JPG, Tithonium Chasma Layers, as seen by

. Image:Ganges Chasma Layers.JPG, Ganges Chasma Layers, as seen by

References

External links