Mars  

Mars as seen by the Hubble Space Telescope
Orbital characteristics[1]
Epoch J2000
Aphelion	249,209,300 km 1.665861 AU
Perihelion	206,669,000 km 1.381497 AU
Semi-major axis	227,939,100 km 1.523679 AU
Eccentricity	0.093315
Orbital period	686.971 day 1.8808 Julian years Look up Mars in Wiktionary, the free dictionary. ... Image File history File links Mars_symbol. ... Image File history File links Mars_Hubble. ... The Hubble Space Telescope (HST; also known colloquially as the Hubble or just Hubble) is a space telescope that was carried into Earth orbit by the Space Shuttle in April 1990. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... The J2000. ... A diagram of Keplerian orbital elements. ... The astronomical unit (AU or au or a. ... A diagram of Keplerian orbital elements. ... The semi-major axis of an ellipse In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae. ... (This page refers to eccitricity in astrodynamics. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... In astronomy, a Julian year is a unit of time defined as exactly 365. ... 668.5991 sols
Synodic period	779.96 day 2.135 Julian years
Average orbital speed	24.077 km/s
Inclination	1.850° 5.65° to Sun's Equator
Longitude of ascending node	49.562°
Argument of perihelion	286.537°
Satellites	2
Physical characteristics
Equatorial radius	3,396.2 ± 0.1 km[a][2] 0.533 Earths
Polar radius	3,376.2 ± 0.1 km[a][2] 0.531 Earths
Flattening	0.00589 ± 0.00015
Surface area	144,798,500 km² 0.284 Earths
Volume	1.6318×1011 km³ 0.151 Earths
Mass	6.4185×1023 kg 0.107 Earths
Mean density	3.934 g/cm³
Equatorial surface gravity	3.69 m/s² 0.376 g
Escape velocity	5.027 km/s
Sidereal rotation period	1.025957 day 24.62296 h
Equatorial rotation velocity	868.22 km/h
Axial tilt	25.19°
North pole right ascension	21 h 10 min 44 s 317.68143°
North pole declination	52.88650°
Albedo	0.15
Surface temp.    Kelvin    Celsius	min mean max 186 K 227 K 268 K[4] −87 °C −46 °C −5 °C
Apparent magnitude	+1.8 to -2.91[3]
Angular diameter	3.5" — 25.1"[3]
Adjectives	Martian
Atmosphere
Surface pressure	0.7–0.9 kPa
Composition	95.72% Carbon dioxide 2.7% Nitrogen 1.6% Argon 0.2% Oxygen 0.07% Carbon monoxide 0.03% Water vapor 0.01% Nitric oxide 2.5 ppm Neon 300 ppb Krypton 130 ppb Formaldehyde 80 ppb Xenon 30 ppb Ozone Various schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... For the science fiction novella by William Shunn, see Inclination (novella). ... Sol redirects here. ... World map showing the equator in red For other uses, see Equator (disambiguation). ... The Longitude of the ascending node (☊, also noted Ω) is one of the orbital elements used to specify the orbit of an object in space. ... The argument of periapsis (ω) is the orbital element describing the angle between an orbiting bodys ascending node (the point where the body crosses the plane of reference from South to North) and its periapsis (the point of closest approach to the central body), measured in the orbital plane and... A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. ... World map showing the equator in red For other uses, see Equator (disambiguation). ... A geographical pole is either of two fixed points on the surface of a spinning body or planet, at 90 degrees from the equator, based on the axis around which a body spins. ... The flattening, ellipticity, or oblateness of an oblate spheroid is the relative difference between its equatorial radius a and its polar radius b: The flattening of the Earth is 1:298. ... In mathematics, a spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. ... For other uses, see Volume (disambiguation). ... For other uses, see Mass (disambiguation). ... For other uses, see Density (disambiguation). ... The surface gravity of a Killing horizon is the acceleration, as exerted at infinity, needed to keep an object at the horizon. ... Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... The term g force or gee force refers to the symbol g, the force of acceleration due to gravity at the earths surface. ... Space Shuttle Atlantis launches on mission STS-71. ... In astronomy, a rotation period is the time an astronomical object takes to complete one revolution around its rotation axis relative to the background stars. ... In astronomy, axial tilt is the inclination angle of a planets rotational axis in relation to a perpendicular to its orbital plane. ... Equatorial Coordinates Right ascension (abbrev. ... In astronomy, declination (abbrev. ... For other uses, see Albedo (disambiguation). ... For other uses, see Temperature (disambiguation). ... For other uses, see Kelvin (disambiguation). ... For other uses, see Celsius (disambiguation). ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... The angular diameter of an object as seen from a given position is the diameter measured as an angle. ... This article is about hypothetical native inhabitants of the planet Mars. ... Atmospheric pressure is the pressure at any given point in the Earths atmosphere. ... For other uses, see Pascal. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... General Name, symbol, number argon, Ar, 18 Chemical series noble gases Group, period, block 18, 3, p Appearance colorless Standard atomic weight 39. ... This article is about the chemical element and its most stable form, or dioxygen. ... Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... Parts per million (ppm) is a measure of concentration that is used where low levels of concentration are significant. ... For other uses, see Neon (disambiguation). ... This page refers to concentration in the chemical sense. ... For other uses, see Krypton (disambiguation). ... This page refers to concentration in the chemical sense. ... Formaldehyde is the chemical compound with the formula H2CO. It is the simplest aldehyde-- an organic compound containing a terminal carbonyl group: it consists of exactly one carbonyl. ... This page refers to concentration in the chemical sense. ... General Name, Symbol, Number xenon, Xe, 54 Chemical series noble gases Group, Period, Block 18, 5, p Appearance colorless Standard atomic weight 131. ... This page refers to concentration in the chemical sense. ... For other uses, see Ozone (disambiguation). ... 10 ppb Methane

Mars (pronounced [ˈmɑːz] (in British English) or [ˈmɑːrz] (in American English) (help·info)) is the fourth planet from the Sun in the Solar System. The planet is named after Mars, the Roman god of war. It is also referred to as the "Red Planet" because of its reddish appearance as seen from Earth. This page refers to concentration in the chemical sense. ... Methane is a chemical compound with the molecular formula . ... This article is about the astronomical term. ... Sol redirects here. ... This article is about the Solar System. ... Mars, painting by Diego Velazquez Mars was the Roman warrior god, the son of Juno and Jupiter, husband of Bellona, and the lover of Venus. ... A head of Minerva found in the ruins of the Roman baths in Bath Roman mythology, the mythological beliefs of the people of Ancient Rome, can be considered as having two parts. ... War Gods redirects here. ... This article is about Earth as a planet. ...

Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts and polar ice caps of Earth. It is the site of Olympus Mons, the highest known mountain in the Solar System, and of Valles Marineris, the largest canyon. In addition to its geographical features, Mars’ rotational period and seasonal cycles are likewise similar to those of Earth. The inner planets, Mercury, Venus, Earth, and Mars, their sizes to scale. ... Atmospheres redirects here. ... Tycho crater on Earths moon. ... This article is about Earths moon. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... Fljótsdalur in East Iceland, a rather flat valley In geology, a valley (also called a vale or dale) is a depression with predominant extent in one direction. ... This article is about arid terrain. ... This article or section does not cite its references or sources. ... This article is about the volcano on Mars and Solar Systems tallest mountain in Latin, For other uses, see Olympus (disambiguation). ... For other uses, see Mountain (disambiguation). ... Valles Marineris cuts a wide swath across the face of Mars Valles Marineris (Latin for Mariner Valley, named after the Mariner 9 Mars orbiter of 1971-72 which discovered it. ... In astronomy, a rotation period is the time an astronomical object takes to complete one revolution around its rotation axis. ... This article or section is in need of attention from an expert on the subject. ...

Until the first flyby of Mars by Mariner 4 in 1965, many speculated that there might be liquid water on the planet's surface. This was based on observations of periodic variations in light and dark patches, particularly in the polar latitudes, which looked like seas and continents, while long, dark striations were interpreted by some observers as irrigation channels for liquid water. These straight line features were later proven not to exist and were instead explained as optical illusions. Still, of all the planets in our Solar System other than Earth, Mars is the most likely to harbor liquid water, and perhaps life.^{[citation needed]} Mariner 4 (Mariner-Mars 1964) was the fourth in a series of spacecraft used for planetary exploration in a flyby mode and performed the first successful flyby of the planet Mars, returning the first pictures of the Martian surface. ... For other uses, see Light (disambiguation). ... Dark redirects here. ... This article is about the geographical term. ... Bodybuilding In bodybuilding, striations are the tiny grooves of muscle across major muscle groups characteristic of a well-developed body. ... An optical illusion. ... This article is about life in general. ...

Mars is currently host to three functional orbiting spacecraft: Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter. This is more than any planet in the Solar System except Earth. The surface is also home to the two Mars Exploration Rovers (Spirit and Opportunity), the lander Phoenix, and several inert landers and rovers that either failed or completed missions. Geological evidence gathered by these and preceding missions suggests that Mars previously had large-scale water coverage, while observations also indicate that small geyser-like water flows have occurred in recent years.^[5] Observations by NASA's Mars Global Surveyor show evidence that parts of the southern polar ice cap have been receding.^[6] The Space Shuttle Discovery as seen from the International Space Station. ... Artists concept of the 2001 Mars Odyssey Spacecraft 2001 Mars Odyssey is an unmanned spacecraft orbiting the planet Mars. ... Concept model of the Mars Express spacecraft Main Engine Thrust for braking manouevre on Venus Express. ... NASAs Mars Reconnaissance Orbiter (MRO) is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. ... Artists Concept of Rover on Mars (credit: Maas Digital LLC) Marvin the Martian, Spirit rover Mission patch Duck Dodgers, Opportunity rover Mission patch NASAs Mars Exploration Rover (MER) Mission is an ongoing robotic mission of exploring Mars, that began in 2003 with the sending of two rovers â€” Spirit... The launch patch for Spirit, featuring Marvin the Martian. ... The launch patch for Opportunity, featuring Duck Dodgers (Daffy Duck). ... A lander is a type of spacecraft which descends to come to rest on the surface of an astronomical body. ... This article is about the Mars lander. ... Strokkur geyser, Iceland A geyser is a type of hot spring that erupts periodically, ejecting a column of hot water and steam into the air. ... For other uses, see NASA (disambiguation). ...

Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Martian Trojan asteroid. Mars can be seen from Earth with the naked eye. Its apparent magnitude reaches −2.9,^[3] a brightness surpassed only by Venus, the Moon, and the Sun, though most of the time Jupiter will appear brighter to the naked eye than Mars. A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. ... Phobos (IPA: or [ˈfoÊŠ.bÉ™s]) (systematic designation: ) is the larger and closer of Mars two moons (the other being Deimos). ... Deimos (IPA or ; Greek Δείμος: Dread), is the smaller and outermost of Mars’ two moons, named after Deimos from Greek Mythology. ... For other uses, see Asteroid (disambiguation). ... 5261 Eureka was discovered at Mt Palomar on June 20, 1990 and turned out to be the first known Mars Trojan asteroid. ... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... For other uses, see Venus (disambiguation). ... For other uses, see Jupiter (disambiguation). ...

Physical characteristics

Size comparison of terrestrial planets (left to right): Mercury, Venus, Earth, and Mars.

Mars has approximately half the radius of Earth and only one-tenth the mass, being less dense, but its surface area is only slightly less than the total area of Earth's dry land.^[3] While Mars is larger and more massive than Mercury, Mercury has a higher density. This results in a slightly stronger gravitational force at Mercury's surface. The red-orange appearance of the Martian surface is caused by iron(III) oxide, more commonly known as hematite, or rust.^[7] Image File history File linksMetadata Download high resolution version (1500x653, 488 KB)Terrestrial planet size comparisons. ... Image File history File linksMetadata Download high resolution version (1500x653, 488 KB)Terrestrial planet size comparisons. ... This article is about the planet. ... For other uses, see Venus (disambiguation). ... This article is about Earth as a planet. ... This article is about an authentication, authorization, and accounting protocol. ... For other uses, see Mass (disambiguation). ... Area is the measure of how much exposed area any two dimensional object has. ... This article is about the planet. ... Iron(III) oxide — also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply rust — is one of the several oxide compounds of iron, and has paramagnetic properties. ...

Geology

Main article: Geology of Mars

Based on orbital observations and the examination of the Martian meteorite collection, the surface of Mars appears to be composed primarily of basalt. Some evidence suggests that a portion of the Martian surface is more silica-rich than typical basalt, and may be similar to andesitic rocks on Earth; however, these observations may also be explained by silica glass. Much of the surface is deeply covered by a fine iron(III) oxide dust that has the consistency of talcum powder.^{[citation needed]} False colour view of a landslide in Zunil crater The geology of Mars, also known as areology (from Greek: Ἂρης, Arēs, Ares; and λόγος, logos, knowledge), refers to the study of the composition, structure, physical properties, history and the processes that shape the planet Mars. ... A Martian meteorite is a meteorite that has landed on Earth but is believed to have originated from Mars. ... For the cities, see Basalt, Colorado and Basalt, Idaho. ... Andesite is an igneous, volcanic (extrusive) rock, of intermediate composition, with aphanitic to porphyritic texture. ... Iron(III) oxide — also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply rust — is one of the several oxide compounds of iron, and has paramagnetic properties. ... Talc block Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2. ...

Rock strewn surface imaged by Mars Pathfinder

Although Mars has no intrinsic magnetic field, observations show that parts of the planet's crust have been magnetized and that alternating polarity reversals of its dipole field have occurred. This paleomagnetism of magnetically susceptible minerals has properties that are very similar to the alternating bands found on the ocean floors of Earth. One theory, published in 1999 and re-examined in October 2005 (with the help of the Mars Global Surveyor), is that these bands demonstrate plate tectonics on Mars 4 billion years ago, before the planetary dynamo ceased to function and caused the planet's magnetic field to fade away.^[8] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The Mars Pathfinder was launched on December 4, 1996 by NASA aboard a Delta II just a month after the Mars Global Surveyor was launched. ... Paleomagnetism refers to the study of the record of the Earths magnetic field preserved in various magnetic minerals through time. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... The Mars Global Surveyor (MGS) was a US spacecraft developed by NASA and the Jet Propulsion Laboratory and launched November 1996. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... One thousand million (1,000,000,000) is the natural number following 999,999,999 and preceding 1,000,000,001. ... The Dynamo theory proposes a mechanism by which a celestial body such as the Earth generates a magnetic field. ...

Current models of the planet's interior imply a core region about 1,480 kilometres in radius, consisting primarily of iron with about 14–17% sulfur. This iron sulfide core is partially fluid, and has twice the concentration of the lighter elements than exist at Earth's core. The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but now appears to be inactive. The average thickness of the planet's crust is about 50 km, with a maximum thickness of 125 km.^[9] Earth's crust, averaging 40 km, is only a third as thick as Mars’ crust relative to the sizes of the two planets. Fe redirects here. ... This article is about the chemical element. ... Iron(II) sulfide is a form of iron sulfide (others include iron pyrite aka Fools Gold), and can be obtained by reacting iron and sulfur under great heat. ... Earth cutaway from core to exosphere. ...

The geological history of Mars can be split into many epochs, but the following are the three main ones:

• Noachian epoch (named after Noachis Terra): Formation of the oldest extant surfaces of Mars, 3.8 billion years ago to 3.5 billion years ago. Noachian age surfaces are scarred by many large impact craters. The Tharsis bulge volcanic upland is thought to have formed during this period, with extensive flooding by liquid water late in the epoch.
• Hesperian epoch (named after Hesperia Planum): 3.5 billion years ago to 1.8 billion years ago. The Hesperian epoch is marked by the formation of extensive lava plains.
• Amazonian epoch (named after Amazonis Planitia): 1.8 billion years ago to present. Amazonian regions have few meteorite impact craters but are otherwise quite varied. Olympus Mons formed during this period along with lava flows elsewhere on Mars.

A major geological event occurred on Mars on February 19, 2008, and was caught on camera by the Mars Reconnaissance Orbiter. Images capturing a spectacular avalanche of materials thought to be fine grained ice, dust, and large blocks are shown to have detached from a 2,300-foot (701 m) high cliff. Evidence of the avalanche is present in the dust clouds left above the cliff afterwards.^[10] Noachis Terra (lit. ... Clouds hover over the volcano peaks of the Tharsis region in this color mosaic image. ... Amazonis Planitia is one of the smoothest plains on Mars. ... This article is about the volcano on Mars and Solar Systems tallest mountain in Latin, For other uses, see Olympus (disambiguation). ... [[Media:Italic text]]{| style=float:right; |- | |- | |} is the 50th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... NASAs Mars Reconnaissance Orbiter (MRO) is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. ...

Hydrology

Photo of microscopic rock forms indicating past signs of water, taken by Opportunity

Liquid water cannot exist on the surface of Mars with its present low atmospheric pressure, except at the lowest elevations for short periods^[11][12] but water ice is in no short supply, with two polar ice caps made largely of ice.^[13] In March 2007, NASA announced that the volume of water ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11 metres.^[14] Additionally, an ice permafrost mantle stretches down from the pole to latitudes of about 60°.^[13] This image taken by MER-B (Mars Rover Opportunity) shows microscopic rock forms indicating past signs of water on Mars. ... This image taken by MER-B (Mars Rover Opportunity) shows microscopic rock forms indicating past signs of water on Mars. ... The launch patch for Opportunity, featuring Duck Dodgers (Daffy Duck). ... While these two men dig in Alaska to study soil, the hard permafrost requires the use of a jackhammer In geology, permafrost or permafrost soil is soil at or below the freezing point of water (0 °C or 32 °F) for two or more years. ...

Much larger quantities of water are thought to be trapped underneath Mars's thick cryosphere, only to be released when the crust is cracked through volcanic action. The largest such release of liquid water is thought to have occurred when the Valles Marineris formed early in Mars's history, enough water being released to form the massive outflow channels. A smaller but more recent event of the same kind may have occurred when the Cerberus Fossae chasm opened about 5 million years ago, leaving a supposed sea of frozen ice still visible today on the Elysium Planitia centered at Cerberus Palus.^[15] However, the morphology of this region is more consistent with the ponding of lava flows causing a superficial similarity to ice flows.^[16] These lava flows probably draped the terrain established by earlier catastrophic floods of Athabasca Valles.^[17] Significantly rough surface texture at decimeter (dm) scales, thermal inertia comparable to that of the Gusev plains, and hydrovolcanic cones are consistent with the lava flow hypothesis.^[17] Furthermore, the stoichiometric mass fraction of H₂O in this area to tens of centimeter depths is only ~4%,^[18] easily attributable to hydrated minerals^[19] and inconsistent with the presence of near-surface ice. The cryosphere, derived from the Greek word kryos for frost or icy cold, is the term which collectively describes the portions of the Earth’s surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps and ice sheets, and frozen ground... Valles Marineris cuts a wide swath across the face of Mars Valles Marineris (Latin for Mariner Valley, named after the Mariner 9 Mars orbiter of 1971-72 which discovered it. ... A 3km section of the Cerberus Fossae fissure, taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) The Cerberus Fossae are a series of semi-parallel fissures on Mars formed by faults which pulled the crust apart in the Cerberus region(9°N, 197°W). ... Look up million in Wiktionary, the free dictionary. ... Elysium Planitia is the second largest volcanic region on Mars, after Tharsis Montes. ...

More recently the high resolution Mars Orbiter Camera on the Mars Global Surveyor has taken pictures which give much more detail about the history of liquid water on the surface of Mars. Despite the many giant flood channels and associated tree-like network of tributaries found on Mars there are no smaller scale structures that would indicate the origin of the flood waters. It has been suggested that weathering processes have denuded these, indicating the river valleys are old features. Higher resolution observations from spacecraft like Mars Global Surveyor also revealed at least a few hundred features along crater and canyon walls that appear similar to terrestrial seepage gullies. The gullies tend to be in the highlands of the southern hemisphere and to face the Equator; all are poleward of 30° latitude.^[20] The researchers found no partially degraded (i.e. weathered) gullies and no superimposed impact craters, indicating that these are very young features. The Mars Global Surveyor (MGS) was a US spacecraft developed by NASA and the Jet Propulsion Laboratory and launched November 1996. ...

Changing gully deposits on Mars

In a particularly striking example (see image) two photographs, taken six years apart, show a gully on Mars with what appears to be new deposits of sediment. Michael Meyer, the lead scientist for NASA's Mars Exploration Program, argues that only the flow of material with a high liquid water content could produce such a debris pattern and colouring. Whether the water results from precipitation, underground or another source remains an open question.^[21] However, alternative scenarios have been suggested, including the possibility of the deposits being caused by carbon dioxide frost or by the movement of dust on the Martian surface.^[22][23] Image File history File links Wateronmars. ... Image File history File links Wateronmars. ...

Further evidence that liquid water once existed on the surface of Mars comes from the detection of specific minerals such as hematite and goethite, both of which sometimes form in the presence of water.^[24] For other uses, see Liquid (disambiguation). ... For other uses, see Hematite (disambiguation). ... Goethite, named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low temperature environments. ...

Nevertheless, some of the evidence believed to indicate ancient water basins and flows has been negated by higher resolution studies taken at resolution about 30 cm by the Mars Reconnaissance Orbiter.^[25]

Geography

Main articles: Geography of Mars, List of mountains on Mars, and List of craters on Mars

See also: Category:Surface features of Mars

This approximate true-color image, taken by the Mars Exploration Rover Opportunity, shows the view of Victoria Crater from Cape Verde. It was captured over a three-week period, from October 16 - November 6, 2006.

Although better remembered for mapping the Moon, Johann Heinrich Mädler and Wilhelm Beer were the first "areographers". They began by establishing once and for all that most of Mars’ surface features were permanent, and determining the planet's rotation period. In 1840, Mädler combined ten years of observations and drew the first map of Mars. Rather than giving names to the various markings, Beer and Mädler simply designated them with letters; Meridian Bay (Sinus Meridiani) was thus feature "a."^[26] Topographic map of Mars, courtesy NASA Goddard Space Flight Center, from Mars Global Surveyor laser altimeter research led by Maria Zuber and David Smith. ... This is a list of all the named mountains on Mars. ... There are hundreds of thousands of craters on Mars, but only some of them have names. ... The launch patch for Opportunity, featuring Duck Dodgers (Daffy Duck). ... Victoria Crater is an impact crater located at 5. ... J. H. von Mädler. ... Wilhelm Beer Wilhelm Wolff Beer (January 14, 1797 – March 27, 1850) was a banker and astronomer in Berlin, Germany, and brother of Giacomo Meyerbeer. ...

Today, features on Mars are named from a number of sources. Large albedo features retain many of the older names, but are often updated to reflect new knowledge of the nature of the features. For example, Nix Olympica (the snows of Olympus) has become Olympus Mons (Mount Olympus).^[27] For other uses, see Albedo (disambiguation). ...

Mars’ equator is defined by its rotation, but the location of its Prime Meridian was specified, as was Earth's (at Greenwich), by choice of an arbitrary point; Mädler and Beer selected a line in 1830 for their first maps of Mars. After the spacecraft Mariner 9 provided extensive imagery of Mars in 1972, a small crater (later called Airy-0), located in the Sinus Meridiani ("Middle Bay" or "Meridian Bay"), was chosen for the definition of 0.0° longitude to coincide with the original selection. Location of the Prime Meridian Image:Prime Meridian. ... This article is about Greenwich in England. ... Mariner 9 launch Mariner 9 (Mariner Mars 71 / Mariner-I) was a NASA space probe orbiter that helped in the exploration of Mars and was part of the Mariner program. ... Airy-0 is a crater on Mars whose location defines the position of the prime meridian of that planet. ... Sinus Meridiani is a classic albedo feature on Mars stretching east-west just south of that planets equator. ...

Olympus Mons

Since Mars has no oceans and hence no 'sea level', a zero-elevation surface or mean gravity surface also had to be selected. Zero altitude is defined by the height at which there is 610.5 Pa (6.105 mbar) of atmospheric pressure. This pressure corresponds to the triple point of water, and is about 0.6% of the sea level surface pressure on Earth.^[28] Image File history File links Download high resolution version (692x1448, 852 KB) Olympus Mons on October 19, 1998, image by the Mars Global Surveyor. ... Image File history File links Download high resolution version (692x1448, 852 KB) Olympus Mons on October 19, 1998, image by the Mars Global Surveyor. ... This article is about the volcano on Mars and Solar Systems tallest mountain in Latin, For other uses, see Olympus (disambiguation). ... Zero-elevation surface is a widely-accepted vertical reference point that is used to describe a surface, such as that of a planet. ... For other uses, see Pascal. ... In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium. ...

The dichotomy of Martian topography is striking: northern plains flattened by lava flows contrast with the southern highlands, pitted and cratered by ancient impacts. The surface of Mars as seen from Earth is thus divided into two kinds of areas, with differing albedo. The paler plains covered with dust and sand rich in reddish iron oxides were once thought of as Martian 'continents' and given names like Arabia Terra (land of Arabia) or Amazonis Planitia (Amazonian plain). The dark features were thought to be seas, hence their names Mare Erythraeum, Mare Sirenum and Aurorae Sinus. The largest dark feature seen from Earth is Syrtis Major.^[29] Arabia Terra is large upland region in the north of Mars. ... Amazonis Planitia is one of the smoothest plains on Mars. ... Mare Erythraeum is a dark dusky region of Mars that can be viewed by even a small telescope. ... a like dark place in the sky. ... Syrtis Major is a dark spot (an albedo feature) located in the boundary between the northern lowlands and southern highlands of Mars. ...

The shield volcano, Olympus Mons (Mount Olympus), at 26 km is the highest known mountain in the Solar System. It is an extinct volcano in the vast upland region Tharsis, which contains several other large volcanoes. It is over three times the height of Mount Everest which in comparison stands at only 8.848 km. Shield volcano A shield volcano is a large volcano with shallow-sloping sides. ... This article is about the volcano on Mars and Solar Systems tallest mountain in Latin, For other uses, see Olympus (disambiguation). ... Clouds hover over the volcano peaks of the Tharsis region in this color mosaic image. ... Everest redirects here. ...

Mars is also scarred by a number of impact craters: a total of 43,000 craters with a diameter of 5 km or greater have been found.^[30] The largest of these is the Hellas impact basin, a light albedo feature clearly visible from Earth.^[31] Due to the smaller mass of Mars, the probability of an object colliding with the planet is about half that of the Earth. However, Mars is located closer to the asteroid belt, so it has an increased chance of being struck by materials from that source. Mars is also more likely to be struck by short-period comets, i.e., those that lie within the orbit of Jupiter.^[32] In spite of this, there are far fewer craters on Mars compared with the Moon because Mars's atmosphere provides protection against small meteors. Some craters have a morphology that suggests the ground was wet when the meteor impacted. Tycho crater on Earths moon. ... NASA image of Hellas Planitia Hellas Planitia, also known as the Hellas Impact Basin, is a roughly circular impact crater located in the southern hemisphere of the planet Mars. ... An albedo feature is a large area on the surface of a planet (or other solar system body) which shows a contrast in brightness or darkness (albedo) with adjacent areas. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... This article is about Earths moon. ...

The large canyon, Valles Marineris (Latin for Mariner Valleys, also known as Agathadaemon in the old canal maps), has a length of 4000 km and a depth of up to 7 km. The length of Valles Marineris is equivalent to the length of Europe and extends across one-fifth the circumference of Mars. By comparison, the Grand Canyon on Earth is only 446 km long and nearly 2 km deep. Valles Marineris was formed due to the swelling of the Tharis area which caused the crust in the area of Valles Marineris to collapse. Another large canyon is Ma'adim Vallis (Ma'adim is Hebrew for Mars). It is 700 km long and again much bigger than the Grand Canyon with a width of 20 km and a depth of 2 km in some places. It is possible that Ma'adim Vallis was flooded with liquid water in the past.^[33] Valles Marineris cuts a wide swath across the face of Mars Valles Marineris (Latin for Mariner Valley, named after the Mariner 9 Mars orbiter of 1971-72 which discovered it. ... Launch of Mariner 1 (NASA) The Mariner program was a program conducted by the American space agency NASA that launched a series of robotic interplanetary probes designed to investigate Mars, Venus and Mercury. ... This article is about the canyon in the southwestern United States. ... Maadim Vallis is one of the largest canyons on Mars, about 700 kilometers long and significantly larger than Earths Grand Canyon. ... The word Hebrew most likely means to cross over, referring to the Semitic people crossing over the Euphrates River. ...

THEMIS image of cave entrances on Mars

Images from the Thermal Emission Imaging System (THEMIS) aboard NASA's Mars Odyssey orbiter have revealed seven possible cave entrances on the flanks of the Arsia Mons volcano.^[34] The caves, named Dena, Chloe, Wendy, Annie, Abbey, Nikki and Jeanne after loved ones of their discoverers, are collectively known as the "seven sisters."^[35] Cave entrances measure from 100 m to 252 m wide and they are believed to be at least 73 m to 96 m deep. Because light does not reach the floor of most of the caves, it is likely that they extend much deeper than these lower estimates and widen below the surface. Dena is the only exception; its floor is visible and was measured to be 130 m deep. The interiors of these caverns may be protected from micrometeoroids, UV radiation, solar flares and high energy particles that bombard the planet's surface.^[36] Some researchers have suggested that this protection makes the caves good candidates for future efforts to find liquid water and signs of life. A THEMIS spectrometer The Thermal Emission Imaging System (THEMIS) is a camera that images Mars in the visible and infrared parts of the spectrum in order to determine the distribution of minerals on the surface of Mars. ... 2001 Mars Odyssey is a robotic spacecraft orbiting the planet Mars. ... For other uses, see Cave (disambiguation). ... Courtesy NASA/JPL-Caltech Arsia Mons is the southernmost of three volcanos (collectively known as Tharsis Montes) on the Tharsis bulge near the equator of the planet Mars. ... A solar flare observed by Hinode in the G-band. ...

Mars has two permanent polar ice caps: the northern one at Planum Boreum and the southern one at Planum Australe. Viking mosaic of Planum Boreale and surrounds. ... Planum Australe, taken by Mars Global Surveyor. ...

Atmosphere

Main article: Atmosphere of Mars

Mars's thin atmosphere, visible on the horizon in this low-orbit photo.

Mars lost its magnetosphere 4 billion years ago, so the solar wind interacts directly with the Martian ionosphere, keeping the atmosphere thinner than it would otherwise be by stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars Express have detected these ionised atmospheric particles trailing off into space behind Mars.^[37][38] The atmosphere of Mars is now relatively thin. Atmospheric pressure on the surface varies from around 30 Pa (0.03 kPa) on Olympus Mons to over 1155 Pa (1.155 kPa) in the depths of Hellas Planitia, with a mean surface level pressure of 600 Pa (0.6 kPa). This is less than 1% of the surface pressure on Earth (101.3 kPa). Mars's mean surface pressure equals the pressure found 35 km above the Earth's surface. The scale height of the atmosphere, about 11 km, is higher than Earth's (6 km) due to the lower gravity. Mars, the fourth planet from the Sun, has a very different atmosphere from that of Earth. ... Image File history File links Size of this preview: 534 × 600 pixel Image in higher resolution (1047 × 1176 pixel, file size: 114 KB, MIME type: image/jpeg) Atmosphere of Mars taken from low orbit. ... Image File history File links Size of this preview: 534 × 600 pixel Image in higher resolution (1047 × 1176 pixel, file size: 114 KB, MIME type: image/jpeg) Atmosphere of Mars taken from low orbit. ... A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... Relationship of the atmosphere and ionosphere The ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. ... The Mars Global Surveyor (MGS) was a US spacecraft developed by NASA and the Jet Propulsion Laboratory and launched November 1996. ... Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. ... Atmospheric pressure is the pressure at any given point in the Earths atmosphere. ... For other uses, see Pascal. ... NASA image of Hellas Planitia Hellas Planitia, also known as the Hellas Impact Basin, is a roughly circular impact crater located in the southern hemisphere of the planet Mars. ... A scale height is a term often used in scientific contexts for a distance over which a quantity decreases by a factor of e. ...

The atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water.^[3] The atmosphere is quite dusty, containing particulates about 1.5 µm in diameter which give the Martian sky a tawny color when seen from the surface.^[39] Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... General Name, symbol, number argon, Ar, 18 Chemical series noble gases Group, period, block 18, 3, p Appearance colorless Standard atomic weight 39. ... This article is about the chemical element and its most stable form, or dioxygen. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length. ... In heraldry, tenné or tawny is a stain, a rarely used tincture, an orangish brown colour. ...

Several researchers claim to have detected methane in the Martian atmosphere with a concentration of about 10 ppb by volume.^[40][41] Since methane is an unstable gas that is broken down by ultraviolet radiation, typically lasting about 340 years in the Martian atmosphere,^[42] its presence would indicate a current or recent source of the gas on the planet. Volcanic activity, cometary impacts, and the presence of methanogenic microbial life forms are among possible sources. It was recently pointed out that methane could also be produced by a non-biological process called serpentinization^[b] involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars.^[43] Methane is a chemical compound with the molecular formula . ... This page refers to concentration in the chemical sense. ... For other uses, see Gas (disambiguation). ... For other uses, see Ultraviolet (disambiguation). ... This article is about volcanoes in geology. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... Methanogens are archaea that produce methane as a metabolic byproduct in anoxic conditions. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... A sample of serpentinite rock, partially made up of chrysotile Serpentinite is a rock comprised of one or more serpentine minerals. ... For other uses, see Mineral (disambiguation). ... The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ...

During a pole's winter, it lies in continuous darkness, chilling the surface and causing 25–30% of the atmosphere to condense out into thick slabs of CO₂ ice (dry ice).^[44] When the poles are again exposed to sunlight, the frozen CO₂ sublimes, creating enormous winds that sweep off the poles as fast as 400 km/h. These seasonal actions transport large amounts of dust and water vapor, giving rise to Earth-like frost and large cirrus clouds. Clouds of water-ice were photographed by the Opportunity rover in 2004.^[45] Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... Dry ice pellet sublimating in water Dry ice block sublimating in air. ... Sublimation of an element or substance is a conversion between the solid and the gas phases with no intermediate