Elemental abundances can be determined remotely by orbiting spacecraft. This map shows the surface concentration (by weight percent) of the element silicon based on data from the Gamma Ray Spectrometer (GRS) Suite on the Mars Odyssey spacecraft. Similar maps exist for a number of other elements.
Mars is differentiated, which—for a terrestrial planet—implies that it has a central core made up of high density matter (mainly metallic iron and nickel) surrounded by a less dense, silicate mantle and crust.[4] Like Earth, Mars appears to have a molten iron core, or at least a molten outer core.[5] However, there does not appear to be convection in the mantle. Presently Mars shows little geological activity.
The elemental composition of Mars is different from Earth's in several significant ways. First, Martian meteorite analysis suggests that the planet's mantle is about twice as rich in iron as the Earth's mantle.[6][7] The planet's distinctive red color is due to iron oxides on its surface. Second, its core is richer in sulphur.[8] Third, the Martian mantle is richer in potassium and phosphorus than Earth's and fourth, the Martian crust contains a higher percentage of volatile elements such as sulphur and chlorine than the Earth's crust does. Many of these conclusions are supported by in situ analyses of rocks and soils on the Martian surface.[9]
Much of what we know about the elemental composition of Mars comes from orbiting spacecraft and landers. (See Exploration of Mars for list.) Most of these spacecraft carry spectrometers and other instruments to measure the surface composition of Mars by either remote sensing from orbit or in situ analyses on the surface. We also have many actual samples of Mars in the form of meteorites that have made their way to Earth. Martian meteorites (often called SNC's, for Shergottites, Nakhlites, and Chassignites[10]—the groups of meteorites first shown to have a martian origin) provide data on the chemical composition of Mars' crust and interior that would not otherwise be available except through a sample return mission.
Based on these data sources, scientists think that the most abundant chemical elements in the Martian crust are silicon, oxygen, iron, magnesium, aluminium, calcium, and potassium. These elements are major components of the minerals comprising igneous rocks.[11] The elements titanium, chromium, manganese, sulfur, phosphorus, sodium, and chlorine are less abundant[12][13] but are still important components of many accessory minerals[14] in rocks and of secondary minerals (weathering products) in the dust and soils (the regolith). On September 5, 2017, scientists reported that the Curiosity rover detected boron, an essential ingredient for life on Earth, on the planet Mars. Such a finding, along with previous discoveries that water may have been present on ancient Mars, further supports the possible early habitability of Gale Crater on Mars.[15][16]
Hydrogen is present as water (H2O) ice and in hydrated minerals. Carbon occurs as carbon dioxide (CO2) in the atmosphere and sometimes as dry ice at the poles. An unknown amount of carbon is also stored in carbonates. Molecular nitrogen (N2) makes up 2.7 percent of the atmosphere. As far as we know, organic compounds are absent[17] except for a trace of methane detected in the atmosphere.[18][19] On 16 December 2014, NASA reported the Curiosity rover detected a "tenfold spike", likely localized, in the amount of methane in the Martian atmosphere. Sample measurements taken "a dozen times over 20 months" showed increases in late 2013 and early 2014, averaging "7 parts of methane per billion in the atmosphere." Before and after that, readings averaged around one-tenth that level.[20][21]
On 25 October 2023, scientists, helped by information from the InSight lander, reported that the planet Mars has a radioactivemagma ocean under its crust.[22]
Mars is fundamentally an igneous planet. Rocks on the surface and in the crust consist predominantly of minerals that crystallize from magma. Most of our current knowledge about the mineral composition of Mars comes from spectroscopic data from orbiting spacecraft, in situ analyses of rocks and soils from six landing sites, and study of the Martian meteorites.[23] Spectrometers currently in orbit include THEMIS (Mars Odyssey), OMEGA (Mars Express), and CRISM (Mars Reconnaissance Orbiter). The two Mars exploration rovers each carry an Alpha Particle X-ray Spectrometer (APXS), a thermal emission spectrometer (Mini-TES), and Mössbauer spectrometer to identify minerals on the surface.
The dark areas of Mars are characterised by the mafic rock-forming minerals olivine, pyroxene, and plagioclasefeldspar. These minerals are the primary constituents of basalt, a dark volcanic rock that also makes up the Earth's oceanic crust and the lunar maria.
Ared Andromeda THEMIS colour image of olivine basalts in the Valles Marineris. Layers rich in olivine appear dark green
The mineral olivine occurs all over the planet, but some of the largest concentrations are in Nili Fossae, an area containing Noachian-aged rocks. Another large olivine-rich outcrop is in Ganges Chasma, an eastern side chasm of Valles Marineris (pictured).[25] Olivine weathers rapidly into clay minerals in the presence of liquid water. Therefore, areas with large outcroppings of olivine-bearing rock indicate that liquid water has not been abundant since the rocks formed.[10]
Pyroxene minerals are also widespread across the surface. Both low-calcium (ortho-) and high-calcium (clino-) pyroxenes are present, with the high-calcium varieties associated with younger volcanic shields and the low-calcium forms (enstatite) more common in the old highland terrain. Because enstatite melts at a higher temperature than its high-calcium cousin, some researchers have argued that its presence in the highlands indicates that older magmas on Mars had higher temperatures than younger ones.[26]
Between 1997 and 2006, the Thermal Emission Spectrometer (TES) on the Mars Global Surveyor (MGS) spacecraft mapped the global mineral composition of the planet.[27] TES identified two global-scale volcanic units on Mars. Surface Type 1 (ST1) characterises the Noachian-aged highlands and consists of unaltered plagioclase- and clinopyroxene-rich basalts. Surface Type 2 (ST2) is common in the younger plains north of the dichotomy boundary and is more silica rich than ST1.
The lavas of ST2 have been interpreted as andesites or basaltic andesites, indicating the lavas in the northern plains originated from more chemically evolved, volatile-rich magmas.[28] (See Igneous differentiation and Fractional crystallization.) However, other researchers have suggested that ST2 represents weathered basalts with thin coatings of silica glass or other secondary minerals that formed through interaction with water- or ice-bearing materials.[29]
True intermediate and felsic rocks are present on Mars, but exposures are uncommon. Both TES and the Thermal Emission Imaging System (THEMIS) on the Mars Odyssey spacecraft have identified high-silica rocks in Syrtis Major and near the southwestern rim of the crater Antoniadi. The rocks have spectra resembling quartz-rich dacites and granitoids, suggesting that at least some parts of the Martian crust may have a diversity of igneous rocks similar to Earth's.[30] Some geophysical evidence suggests that the bulk of the Martian crust may actually consist of basaltic andesite or andesite. The andesitic crust is hidden by overlying basaltic lavas that dominate the surface composition but are volumetrically minor.[4]
Rocks studied by Spirit Rover in Gusev crater can be classified in different ways. The amounts and types of minerals make the rocks primitive basalts—also called picritic basalts. The rocks are similar to ancient terrestrial rocks called basaltic komatiites. Rocks of the plains also resemble the basaltic shergottites, meteorites which came from Mars. One classification system compares the amount of alkali elements to the amount of silica on a graph; in this system, Gusev plains rocks lie near the junction of basalt, picrobasalt, and tephrite. The Irvine-Barager classification calls them basalts.[31]
Curiosity rover – view of "Sheepbed" mudstone (lower left) and surroundings (February 14, 2013).
In the journal Science from September 2013, researchers described a different type of rock called "Jake M" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the Curiosity rover, and it was different from other known martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).[35]
On December 9, 2013, NASA researchers described, in a series of six articles in the journal Science, many new discoveries from the Curiosity rover. Possible organics were found that could not be explained by contamination.[36][37] Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.[38][39][40] Because much of the carbon was released at a relatively low temperature in Curiosity's Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. The carbon could be from organisms, but this has not been proven. This organic-bearing material was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called “Sheepbed mudstone”. The samples were named John Klein and Cumberland. Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.”[41] However, in this process only a very tiny amount of carbon is involved — much less than was found at Yellowknife Bay.[42][43]
Using SAM's mass spectrometer, scientists measured isotopes of helium, neon, and argon that cosmic rays produce as they go through rock. The fewer of these isotopes they find, the more recently the rock has been exposed near the surface. The 4-billion-year-old lakebed rock drilled by Curiosity was uncovered between 30 million and 110 million years ago by winds which sandblasted away 2 meters of overlying rock. Next, they hope to find a site tens of millions of years younger by drilling close to an overhanging outcrop.[44]
The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. These measurements are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long potential organic biosignatures can be preserved. This study estimates that a few meters drill is necessary to access possible biomolecules.[45] The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these measurements, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. Exposure to 1 sievert is associated with a 5 percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is 3 percent.[46] Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.[45]
The samples examined were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species.[38][47][48][49] These types of iron and sulfur could have been used by living organisms.[50]C, H, O, S, N, and P were measured directly as key biogenic elements, and by inference, P is assumed to have been there as well.[41][43] The two samples, John Klein and Cumberland, contain basaltic minerals, Ca-sulfates, Fe oxide/hydroxides, Fe-sulfides, amorphous material, and trioctahedral smectites (a type of clay). Basaltic minerals in the mudstone are similar to those in nearby aeoliandeposits. However, the mudstone has far less Fe-forsterite plus magnetite, so Fe-forsterite (type of olivine) was probably altered to form smectite (a type of clay) and magnetite.[51] A Late Noachian/EarlyHesperian or younger age indicates that clay mineral formation on Mars extended beyond Noachian time; therefore, in this location neutral pH lasted longer than previously thought.[47]
Much of the Martian surface is deeply covered by dust as fine as talcum powder. The global predominance of dust obscures the underlying bedrock, making spectroscopic identification of primary minerals impossible from orbit over many areas of the planet. The red/orange appearance of the dust is caused by iron(III) oxide (nanophase Fe2O3) and the iron(III) oxide-hydroxide mineral goethite.[54]
The global dust cover and the presence of other wind-blown sediments has made soil compositions remarkably uniform across the Martian surface. Analysis of soil samples from the Viking landers in 1976 shows that the soils consist of finely broken up basaltic rock fragments and are highly enriched in sulphur and chlorine, probably derived from volcanic gas emissions.[56]
Opaline silica and iron sulphate minerals form in acidic (low pH) solutions. Sulphates have been found in a variety of locations, including near Juventae Chasma, Ius Chasma, Melas Chasma, Candor Chasma, and Ganges Chasma. These sites all contain fluvial landforms indicating that abundant water was once present.[57] Spirit rover discovered sulfates and goethite in the Columbia Hills.[58][59]
Some of the mineral classes detected may have formed in environments suitable (i.e., enough water and the proper pH) for life. The mineral smectite (a phyllosilicate) forms in near-neutral waters. Phyllosilicates and carbonates are good for preserving organic matter, so they may contain evidence of past life.[60][61] Sulfate deposits preserve chemical and morphological fossils, and fossils of microorganisms form in iron oxides like hematite.[62] The presence of opaline silica points toward a hydrothermal environment that could support life. Silica is also excellent for preserving evidence of microbes.[63]
Sedimentary rocks
Cross-bedded sandstones inside Victoria Crater.Huygens Crater with circle showing place where carbonate was discovered. This deposit may represent a time when Mars had abundant liquid water on its surface. Scale bar is 250 kilometres (160mi) long.
Layered sedimentary deposits are widespread on Mars. These deposits probably consist of both sedimentary rock and poorly indurated or unconsolidated sediments. Thick sedimentary deposits occur in the interior of several canyons in Valles Marineris, within large craters in Arabia and Meridiani Planum (see Henry Crater for example), and probably comprise much of the deposits in the northern lowlands (e.g., Vastitas Borealis Formation). The Mars Exploration Rover Opportunity landed in an area containing cross-bedded (mainly eolian) sandstones (Burns formation[64]). Fluvial-deltaic deposits are present in Eberswalde Crater and elsewhere, and photogeologic evidence suggests that many craters and low lying intercrater areas in the southern highlands contain Noachian-aged lake sediments.
While the possibility of carbonates on Mars has been of great interest to astrobiologists and geochemists alike, there was little evidence for significant quantities of carbonate deposits on the surface. In the summer of 2008, the TEGA and WCL experiments on the 2007 Phoenix Mars lander found between 3–5wt% (percent by weight) calcite (CaCO3) and an alkaline soil.[65] In 2010, analyses by the Mars Exploration Rover Spirit identified outcrops rich in magnesium-iron carbonate (16–34 wt%) in the Columbia Hills of Gusev crater. The magnesium-iron carbonate most likely precipitated from carbonate-bearing solutions under hydrothermal conditions at near-neutral pH in association with volcanic activity during the Noachian Period.[66]
Carbonates (calcium or iron carbonates) were discovered in a crater on the rim of Huygens Crater, located in the Iapygia quadrangle. The impact on the rim exposed material that had been dug up from the impact that created Huygens. These minerals represent evidence that Mars once had a thicker carbon dioxide atmosphere with abundant moisture, since these kind of carbonates only form when there is a lot of water. They were found with the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the Mars Reconnaissance Orbiter. Earlier, the instrument had detected clay minerals. The carbonates were found near the clay minerals. Both of these minerals form in wet environments. It is supposed that billions of years ago Mars was much warmer and wetter. At that time, carbonates would have formed from water and the carbon dioxide-rich atmosphere. Later the deposits of carbonate would have been buried. The double impact has now exposed the minerals. Earth has vast carbonate deposits in the form of limestone.[67]
Spirit Rover discoveries in the Aeolis quadrangle
The rocks on the plains of Gusev are a type of basalt. They contain the mineralsolivine, pyroxene, plagioclase, and magnetite, and they look like volcanic basalt as they are fine-grained with irregular holes (geologists would say they have vesicles and vugs).[68][69] Much of the soil on the plains came from the breakdown of the local rocks. Fairly high levels of nickel were found in some soils; probably from meteorites.[70] Analysis shows that the rocks have been slightly altered by tiny amounts of water. Outside coatings and cracks inside the rocks suggest water deposited minerals, maybe bromine compounds. All the rocks contain a fine coating of dust and one or more harder rinds of material. One type can be brushed off, while another needed to be ground off by the Rock Abrasion Tool (RAT).[71]
There are a variety of rocks in the Columbia Hills (Mars), some of which have been altered by water, but not by very much water.
The dust in Gusev Crater is the same as dust all around the planet. All the dust was found to be magnetic. Moreover, Spirit found the magnetism was caused by the mineral magnetite, especially magnetite that contained the element titanium. One magnet was able to completely divert all dust hence all Martian dust is thought to be magnetic.[55] The spectra of the dust was similar to spectra of bright, low thermal inertia regions like Tharsis and Arabia that have been detected by orbiting satellites. A thin layer of dust, maybe less than one millimeter thick covers all surfaces. Something in it contains a small amount of chemically bound water.[72][73]
Plains
Adirondack
Above: An approximate true-color view of Adirondack, taken by Spirit's pancam. Right: Digital camera image (from Spirit's Pancam) of Adirondack after a RAT grind (Spirit's rock grinding tool)
Observations of rocks on the plains show they contain the minerals pyroxene, olivine, plagioclase, and magnetite. These rocks can be classified in different ways. The amounts and types of minerals make the rocks primitive basalts—also called picritic basalts. The rocks are similar to ancient terrestrial rocks called basaltic komatiites. Rocks of the plains also resemble the basaltic shergottites, meteorites which came from Mars. One classification system compares the amount of alkali elements to the amount of silica on a graph; in this system, Gusev plains rocks lie near the junction of basalt, picrobasalt, and tephrite. The Irvine-Barager classification calls them basalts.[31] Plain's rocks have been very slightly altered, probably by thin films of water because they are softer and contain veins of light colored material that may be bromine compounds, as well as coatings or rinds. It is thought that small amounts of water may have gotten into cracks inducing mineralization processes).[31][69] Coatings on the rocks may have occurred when rocks were buried and interacted with thin films of water and dust. One sign that they were altered was that it was easier to grind these rocks compared to the same types of rocks found on Earth.
The first rock that Spirit studied was Adirondack. It turned out to be typical of the other rocks on the plains.
Columbia Hills
Scientists found a variety of rock types in the Columbia Hills, and they placed them into six different categories. The six are: Adirondack, Clovis, Wishstone, Peace, Watchtower, Backstay, and Independence. They are named after a prominent rock in each group. Their chemical compositions, as measured by APXS, are significantly different from each other.[74] Most importantly, all of the rocks in Columbia Hills show various degrees of alteration due to aqueous fluids.[75] They are enriched in the elements phosphorus, sulfur, chlorine, and bromine—all of which can be carried around in water solutions. The Columbia Hills' rocks contain basaltic glass, along with varying amounts of olivine and sulfates.[76][58] The olivine abundance varies inversely with the amount of sulfates. This is exactly what is expected because water destroys olivine but helps to produce sulfates.
The Clovis group is especially interesting because the Mossbauer spectrometer (MB) detected goethite in it.[59] Goethite forms only in the presence of water, so its discovery is the first direct evidence of past water in the Columbia Hills's rocks. In addition, the MB spectra of rocks and outcrops displayed a strong decline in olivine presence, although the rocks probably once contained much olivine.[77] Olivine is a marker for the lack of water because it easily decomposes in the presence of water. Sulfate was found, and it needs water to form.
Wishstone contained a great deal of plagioclase, some olivine, and anhydrate (a sulfate). Peace rocks showed sulfur and strong evidence for bound water, so hydrated sulfates are suspected. Watchtower class rocks lack olivine consequently they may have been altered by water. The Independence class showed some signs of clay (perhaps montmorillonite a member of the smectite group). Clays require fairly long term exposure to water to form.
One type of soil, called Paso Robles, from the Columbia Hills, may be an evaporate deposit because it contains large amounts of sulfur, phosphorus, calcium, and iron.[78] Also, MB found that much of the iron in Paso Robles soil was of the oxidized, Fe+++ form, which would happen if water had been present.[72]
Towards the middle of the six-year mission (a mission that was supposed to last only 90 days), large amounts of pure silica were found in the soil. The silica could have come from the interaction of soil with acid vapors produced by volcanic activity in the presence of water or from water in a hot spring environment.[79]
After Spirit stopped working scientists studied old data from the Miniature Thermal Emission Spectrometer, or Mini-TES and confirmed the presence of large amounts of carbonate-rich rocks, which means that regions of the planet may have once harbored water. The carbonates were discovered in an outcrop of rocks called "Comanche."[80][81]
In summary, Spirit found evidence of slight weathering on the plains of Gusev, but no evidence that a lake was there. However, in the Columbia Hills there was clear evidence for a moderate amount of aqueous weathering. The evidence included sulfates and the minerals goethite and carbonates which only form in the presence of water. It is believed that Gusev crater may have held a lake long ago, but it has since been covered by igneous materials. All the dust contains a magnetic component which was identified as magnetite with some titanium. Furthermore, the thin coating of dust that covers everything on Mars is the same in all parts of the planet.
Opportunity rover discoveries in the Margaritifer Sinus quadrangle
This image, taken by the microscopic imager, reveals shiny, spherical objects embedded within the trench wall
"Blueberries" (hematite spheres) on a rocky outcrop at Eagle Crater. Note the merged triplet in the upper left.
Drawing showing how "blueberries" came to cover much of surface in Meridiani Planum.
The rock "Berry Bowl".
Opportunity Rover found that the soil at Meridiani Planum was very similar to the soil at Gusev crater and Ares Vallis; however in many places at Meridiani the soil was covered with round, hard, gray spherules that were named "blueberries."[82] These blueberries were found to be composed almost entirely of the mineral hematite. It was decided that the spectra signal spotted from orbit by Mars Odyssey was produced by these spherules. After further study it was decided that the blueberries were concretions formed in the ground by water.[72] Over time, these concretions weathered from what was overlying rock, and then became concentrated on the surface as a lag deposit. The concentration of spherules in bedrock could have produced the observed blueberry covering from the weathering of as little as one meter of rock.[83][84] Most of the soil consisted of olivine basalt sands that did not come from the local rocks. The sand may have been transported from somewhere else.[85]
Minerals in dust
A Mössbauer spectrograph was made of the dust that gathered on Opportunity's capture magnet. The results suggested that the magnetic component of the dust was titanomagnetite, rather than just plain magnetite, as was once thought. A small amount of olivine was also detected which was interpreted as indicating a long arid period on the planet. On the other hand, a small amount of hematite that was present meant that there may have been liquid water for a short time in the early history of the planet.[86]
Because the Rock Abrasion Tool (RAT) found it easy to grind into the bedrocks, it is thought that the rocks are much softer than the rocks at Gusev crater.[citation needed]
The rocks contained the sulfates had a light tone compared to isolated rocks and rocks examined by landers/rovers at other locations on Mars. The spectra of these light toned rocks, containing hydrated sulfates, were similar to spectra taken by the Thermal Emission Spectrometer on board the Mars Global Surveyor. The same spectrum is found over a large area, so it is believed that water once appeared over a wide region, not just in the area explored by Opportunity Rover.[90]
The Alpha Particle X-ray Spectrometer (APXS) found rather high levels of phosphorus in the rocks. Similar high levels were found by other rovers at Ares Vallis and Gusev Crater, so it has been hypothesized that the mantle of Mars may be phosphorus-rich.[91] The minerals in the rocks could have originated by acid weathering of basalt. Because the solubility of phosphorus is related to the solubility of uranium, thorium, and rare earth elements, they are all also expected to be enriched in rocks.[92]
When Opportunity rover traveled to the rim of Endeavour crater, it soon found a white vein that was later identified as being pure gypsum.[93][94] It was formed when water carrying gypsum in solution deposited the mineral in a crack in the rock. A picture of this vein, called "Homestake" formation, is shown below.
Cross-bedding features in rock "Last Chance".Voids or "vugs" inside the rock
Heat Shield Rock was the first meteorite ever identified on another planet.
Heat shield, with Heat Shield Rock just above and to the left in the background.
Examination in 2004 of Meridiani rocks, showed the first strong in situ evidence for past water by detecting the mineral jarosite, which only forms in water. This discovery proved that water once existed in Meridiani Planum.[95] In addition, some rocks showed small laminations (layers) with shapes that are only made by gently flowing water.[96] The first such laminations were found in a rock called "The Dells." Geologists would say that the cross-stratification showed festoon geometry from transport in subaqueous ripples.[89] A picture of cross-stratification, also called cross-bedding, is shown on the left.
Box-shaped holes in some rocks were caused by sulfates forming large crystals, and then when the crystals later dissolved, holes, called vugs, were left behind.[96] The concentration of the element bromine in rocks was highly variable probably because it is very soluble. Water may have concentrated it in places before it evaporated. Another mechanism for concentrating highly soluble bromine compounds is frost deposition at night that would form very thin films of water that would concentrate bromine in certain spots.[82]
Rock from impact
One rock, "Bounce Rock," found sitting on the sandy plains was found to be ejecta from an impact crater. Its chemistry was different from the bedrocks. Containing mostly pyroxene and plagioclase and no olivine, it closely resembled a part, Lithology B, of the shergottite meteorite EETA 79001, a meteorite known to have come from Mars. Bounce rock received its name by being near an airbag bounce mark.[83]
Meteorites
Opportunity Rover found meteorites just sitting on the plains. The first one analyzed with Opportunity's instruments was called "Heatshield Rock," as it was found near where Opportunity's heatshield landed. Examination with the Miniature Thermal Emission Spectrometer (Mini-TES), Mossbauer spectrometer, and APXS lead researchers to, classify it as an IAB meteorite. The APXS determined it was composed of 93% iron and 7% nickel. The cobble named "Fig Tree Barberton" is thought to be a stony or stony-iron meteorite (mesosiderite silicate),[97] while "Allan Hills," and "Zhong Shan" may be iron meteorites.
Geological history
Observations at the site have led scientists to believe that the area was flooded with water a number of times and was subjected to evaporation and desiccation.[83] In the process sulfates were deposited. After sulfates cemented the sediments, hematite concretions grew by precipitation from groundwater. Some sulfates formed into large crystals which later dissolved to leave vugs. Several lines of evidence point toward an arid climate in the past billion years or so, but a climate supporting water, at least for a time, in the distant past.[98]
Curiosity Rover discoveries in the Aeolis quadrangle
On September 27, 2012, NASA scientists announced that the Curiosity rover found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.[1][2][3]
On 16 December 2014, NASA reported the Curiosity rover detected a "tenfold spike", likely localized, in the amount of methane in the Martian atmosphere. Sample measurements taken "a dozen times over 20 months" showed increases in late 2013 and early 2014, averaging "7 parts of methane per billion in the atmosphere." Before and after that, readings averaged around one-tenth that level.[20][21]
NASA's Mars Exploration Rover (MER) mission was a robotic space mission involving two Mars rovers, Spirit and Opportunity, exploring the planet Mars. It began in 2003 with the launch of the two rovers to explore the Martian surface and geology; both landed on Mars at separate locations in January 2004. Both rovers far outlived their planned missions of 90 Martian solar days: MER-A Spirit was active until March 22, 2010, while MER-B Opportunity was active until June 10, 2018.
Gusev is a crater on the planet Mars and is located at 14.5°S 175.4°E and is in the Aeolis quadrangle. The crater is about 166 kilometers in diameter and formed approximately three to four billion years ago. It was named after Russian astronomer Matvey Gusev (1826–1866) in 1976.
Meridiani Planum (alternatively Terra Meridiani) is a large plain straddling the equator of Mars. The plain sits on top of an enormous body of sediments that contains a lot of bound water. The iron oxide in the spherules is crystalline (grey) hematite (Fe2O3).
Sinus Meridiani is an albedo feature on Mars stretching east-west just south of the planet's equator. It was named by the French astronomer Camille Flammarion in the late 1870s.
Martian spherules (also known as hematite spherules, blueberries, & Martian blueberries) are small spherules (roughly spherical pebbles) that are rich in an iron oxide (grey hematite, α-Fe2O3) and are found at Meridiani Planum (a large plain on Mars) in exceedingly large numbers.
The Columbia Hills are a range of low hills inside Gusev crater on Mars. They were observed by the Mars Exploration Rover Spirit when it landed within the crater in 2004. They were promptly given an unofficial name by NASA since they were the most striking nearby feature on the surface. The hills lie approximately 3 kilometres (1.9 mi) away from the rover's original landing position. The range is named to memorialize the Space Shuttle Columbia disaster. On February 2, 2004, the individual peaks of the Columbia Hills were named after the seven astronauts who died in the disaster. Spirit spent a few years exploring the Columbia Hills until it ceased to function in 2010. It was also considered a potential landing site for the Mars 2020 Perseverance rover, before the selection of Jezero crater in November 2018.
Heat Shield Rock is a basketball-sized iron-nickel meteorite found on the Meridiani Planum plain of Mars by the Mars rover Opportunity in January 2005.
NASA's 2003 Mars Exploration Rover Mission has amassed an enormous amount of scientific information related to the Martian geology and atmosphere, as well as providing some astronomical observations from Mars. This article covers information gathered by the Opportunity rover during the initial phase of its mission. Information on science gathered by Spirit can be found mostly in the Spirit rover article.
The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) was a visible-infrared spectrometer aboard the Mars Reconnaissance Orbiter searching for mineralogic indications of past and present water on Mars. The CRISM instrument team comprised scientists from over ten universities and was led by principal investigator Scott Murchie. CRISM was designed, built, and tested by the Johns Hopkins University Applied Physics Laboratory.
The formation of carbonates on Mars have been suggested based on evidence of the presence of liquid water and atmospheric carbon dioxide in the planet's early stages. Moreover, due to their utility in registering changes in environmental conditions such as pH, temperature, fluid composition, carbonates have been considered as a primary target for planetary scientists' research. However, since their first detection in 2008, the large deposits of carbonates that were one expected on Mars have not been found, leading to multiple potential explanations that can explain why carbonates did not form massively on the planet.
Martian soil is the fine regolith found on the surface of Mars. Its properties can differ significantly from those of terrestrial soil, including its toxicity due to the presence of perchlorates. The term Martian soil typically refers to the finer fraction of regolith. So far, no samples have been returned to Earth, the goal of a Mars sample-return mission, but the soil has been studied remotely with the use of Mars rovers and Mars orbiters.
The Lunae Palus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is also referred to as MC-10. Lunae Planum and parts of Xanthe Terra and Chryse Planitia are found in the Lunae Palus quadrangle. The Lunae Palus quadrangle contains many ancient river valleys.
The Aeolis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Aeolis quadrangle is also referred to as MC-23 . The Aeolis quadrangle covers 180° to 225° W and 0° to 30° south on Mars, and contains parts of the regions Elysium Planitia and Terra Cimmeria. A small part of the Medusae Fossae Formation lies in this quadrangle.
The Margaritifer Sinus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Margaritifer Sinus quadrangle is also referred to as MC-19. The Margaritifer Sinus quadrangle covers the area from 0° to 45° west longitude and 0° to 30° south latitude on Mars. Margaritifer Sinus quadrangle contains Margaritifer Terra and parts of Xanthe Terra, Noachis Terra, Arabia Terra, and Meridiani Planum.
Almost all water on Mars today exists as ice, though it also exists in small quantities as vapor in the atmosphere. What was thought to be low-volume liquid brines in shallow Martian soil, also called recurrent slope lineae, may be grains of flowing sand and dust slipping downhill to make dark streaks. While most water ice is buried, it is exposed at the surface across several locations on Mars. In the mid-latitudes, it is exposed by impact craters, steep scarps and gullies. Additionally, water ice is also visible at the surface at the north polar ice cap. Abundant water ice is also present beneath the permanent carbon dioxide ice cap at the Martian south pole. More than 5 million km3 of ice have been detected at or near the surface of Mars, enough to cover the whole planet to a depth of 35 meters (115 ft). Even more ice might be locked away in the deep subsurface. Some liquid water may occur transiently on the Martian surface today, but limited to traces of dissolved moisture from the atmosphere and thin films, which are challenging environments for known life. No evidence of present-day liquid water has been discovered on the planet's surface because under typical Martian conditions, warming water ice on the Martian surface would sublime at rates of up to 4 meters per year. Before about 3.8 billion years ago, Mars may have had a denser atmosphere and higher surface temperatures, potentially allowing greater amounts of liquid water on the surface, possibly including a large ocean that may have covered one-third of the planet. Water has also apparently flowed across the surface for short periods at various intervals more recently in Mars' history. Aeolis Palus in Gale Crater, explored by the Curiosity rover, is the geological remains of an ancient freshwater lake that could have been a hospitable environment for microbial life. The present-day inventory of water on Mars can be estimated from spacecraft images, remote sensing techniques, and surface investigations from landers and rovers. Geologic evidence of past water includes enormous outflow channels carved by floods, ancient river valley networks, deltas, and lakebeds; and the detection of rocks and minerals on the surface that could only have formed in liquid water. Numerous geomorphic features suggest the presence of ground ice (permafrost) and the movement of ice in glaciers, both in the recent past and present. Gullies and slope lineae along cliffs and crater walls suggest that flowing water continues to shape the surface of Mars, although to a far lesser degree than in the ancient past.
The mineralogy of Mars is the chemical composition of rocks and soil that encompass the surface of Mars. Various orbital crafts have used spectroscopic methods to identify the signature of some minerals. The planetary landers performed concrete chemical analysis of the soil in rocks to further identify and confirm the presence of other minerals. The only samples of Martian rocks that are on Earth are in the form of meteorites. The elemental and atmospheric composition along with planetary conditions is essential in knowing what minerals can be formed from these base parts.
Mars may contain ores that would be very useful to potential colonists. The abundance of volcanic features together with widespread cratering are strong evidence for a variety of ores. While nothing may be found on Mars that would justify the high cost of transport to Earth, the more ores that future colonists can obtain from Mars, the easier it would be to build colonies there.
To date, interplanetary spacecraft have provided abundant evidence of water on Mars, dating back to the Mariner 9 mission, which arrived at Mars in 1971. This article provides a mission by mission breakdown of the discoveries they have made. For a more comprehensive description of evidence for water on Mars today, and the history of water on that planet, see Water on Mars.
Rain and snow was a regular occurrence on Mars in the past; especially in the Noachian and early Hesperian epochs. Water was theorized to seep into the ground until it reached a formation that would not allow it to penetrate further. Water then accumulated forming a saturated layer. Deep aquifers may still exist.
Rocknest is a sand patch on the surface of Aeolis Palus, between Peace Vallis and Aeolis Mons, in Gale crater on the planet Mars. The patch was encountered by the Curiosity rover on the way from Bradbury Landing to Glenelg Intrigue on September 28, 2012. The approximate site coordinates are: 4.59°S 137.44°E.
↑ Barlow, N.G. (2008). Mars: An Introduction to Its Interior, Surface, and Atmosphere. Cambridge, UK: Cambridge University Press. p.42. ISBN978-0-521-85226-5.
↑ Halliday, A. N. et al. (2001). The Accretion, Composition and Early Differentiation of Mars. In Chronology and Evolution of Mars, Kallenbach, R. et al. Eds., Space Science Reviews,96: pp. 197–230.
↑ Treiman, A; Drake, M; Janssens, M; Wolf, R; Ebihara, M (1986). "Core Formation in the Earth and the Shergottite Parent Body". Geochimica et Cosmochimica Acta. 50 (6): 1071–1091. Bibcode:1986GeCoA..50.1071T. doi:10.1016/0016-7037(86)90389-3.
↑ See Bruckner, J. et al. (2008) Mars Exploration Rovers: Chemical Composition by the APX, in The Martian Surface: Composition, Mineralogy, and Physical Properties, J.F. Bell III, Ed.; Cambridge University Press: Cambridge, UK, p.58 for example.
1 2 Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; etal., eds. (1992). Mars. Tucson: University of Arizona Press. p.[pageneeded]. ISBN978-0-8165-1257-7.
↑ Press, F.; Siever, R. (1978). Earth, 2nd ed.; W.H. Freeman: San Francisco, p. 343.
↑ Foley, C.N. et al. (2008). Martian Surface Chemistry: APXS Results from the Pathfinder Landing Site, in The Martian Surface: kaala, Mineralogy, and Physical Properties, J.F. Bell III, Ed. Cambridge University Press: Cambridge, UK, pp. 42–43, Table 3.1.
↑ Klein, H.P.; etal. (1992). "The Search for Extant Life on Mars". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; etal. (eds.). Mars. Tucson: University of Arizona Press. p.1227. ISBN978-0-8165-1257-7.
↑ Soderblom, L.A.; Bell, J.F. (2008). "Exploration of the Martian Surface: 1992–2007". In J.F. Bell III (ed.). The Martian Surface: Composition, Mineralogy, and Physical Properties. Cambridge, UK: Cambridge University Press. p.11. Bibcode:2008mscm.book.....B.
↑ Christensen, P.R.; etal. (2008). "Global Mineralogy Mapped from the Mars Global Surveyor Thermal Emission Spectrometer". In J. Bell (ed.). The Martian Surface: Composition, Mineralogy, and Physical Properties. Cambridge, UK: Cambridge University Press. p.197. Bibcode:2008mscm.book.....B.
↑ McSween, etal. 2004. Basaltic Rocks Analyzed by the Spirit Rover in Gusev Crater. Science: 305. 842–845
1 2 Arvidson, R. E., et al. (2004) Science, 305, 821–824
↑ Gelbert, R., et al. 2006. The Alpha Particle X-ray Spectrometer (APXS): results from Gusev crater and calibration report. J. Geophys. Res. – Planets: 111.
↑ Christensen, P. Initial Results from the Mini-TES Experiment in Gusev Crater from the Spirit Rover. Science: 305. 837–842.
↑ Gelbert, R. et al. Chemistry of Rocks and Soils in Gusev Crater from the Alpha Particle X-ray Spectrometer. Science: 305. 829-305
↑ Squyres, Steven W.; Arvidson, Raymond E.; Blaney, Diana L.; Clark, Benton C.; Crumpler, Larry; Farrand, William H.; Gorevan, Stephen; Herkenhoff, Kenneth E.; Hurowitz, Joel; Kusack, Alastair; McSween, Harry Y.; Ming, Douglas W.; Morris, Richard V.; Ruff, Steven W.; Wang, Alian; Yen, Albert (February 2006). "Rocks of the Columbia Hills". Journal of Geophysical Research: Planets. 111 (E2): E02S11. Bibcode:2006JGRE..111.2S11S. doi:10.1029/2005JE002562.
↑ Morris, R. V.; Klingelhöfer, G.; Schröder, C.; Rodionov, D. S.; Yen, A.; Ming, D. W.; de Souza, P. A.; Fleischer, I.; Wdowiak, T.; Gellert, R.; Bernhardt, B.; Evlanov, E. N.; Zubkov, B.; Foh, J.; Bonnes, U.; Kankeleit, E.; Gütlich, P.; Renz, F.; Squyres, S. W.; Arvidson, R. E. (February 2006). "Mössbauer mineralogy of rock, soil, and dust at Gusev crater, Mars: Spirit's journey through weakly altered olivine basalt on the plains and pervasively altered basalt in the Columbia Hills". Journal of Geophysical Research: Planets. 111 (E2): E02S13. Bibcode:2006JGRE..111.2S13M. doi:10.1029/2005JE002584. hdl:1893/17159.
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