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A Martian meteorite is a rock that formed on
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...
, was ejected from the planet by an
impact event An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or me ...
, and traversed
interplanetary space Interplanetary may refer to: *Interplanetary space, the space between the planets of the Solar System *Interplanetary spaceflight, travel between planets *The interplanetary medium, the material that exists in interplanetary space *The InterPlanet ...
before landing on
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
as a
meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...
. , 277 meteorites had been classified as Martian, less than half a percent of the 72,000 meteorites that have been classified. The largest complete, uncut Martian meteorite, Taoudenni 002, was recovered in Mali in early 2021. It weighs 14.5 kilograms (32 pounds) and is on display at the Maine Mineral & Gem Museum. There are three
groups A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic ide ...
of Martian meteorite:
shergottites A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. , 277 meteorites had been classified as Martian, less than half a percen ...
,
nakhlites Nakhlites are a group of Martian meteorites, named after the first one, Nakhla meteorite. Nakhlites are igneous rocks that are rich in augite and were formed from basaltic magma about 1.3 billion years ago. They contain augite and olivine cry ...
and
chassignites A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. , 277 meteorites had been classified as Martian, less than half a perc ...
, collectively known as SNC meteorites. Several other Martian meteorites are ungrouped. These meteorites are interpreted as Martian because they have
elemental An elemental is a mythic being that is described in occult and alchemical works from around the time of the European Renaissance, and particularly elaborated in the 16th century works of Paracelsus. According to Paracelsus and his subsequent fo ...
and isotopic compositions that are similar to
rocks In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's ...
and atmospheric gases on Mars, which have been measured by orbiting spacecraft, surface landers and rovers. The term does not include meteorites found on Mars, such as
Heat Shield Rock 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. Informally referred to as "Heat Shield Rock" by the Opportunity research team, the m ...
.


History

By the early 1980s, it was obvious that the SNC group of meteorites (Shergottites, Nakhlites, Chassignites) were significantly different from most other meteorite types. Among these differences were younger formation ages, a different oxygen isotopic composition, the presence of aqueous weathering products, and some similarity in chemical composition to analyses of the Martian surface rocks in 1976 by the Viking landers. Several scientists suggested these characteristics implied the origin of SNC meteorites from a relatively large parent body, possibly Mars. Then in 1983, various trapped gases were reported in impact-formed glass of the EET79001 shergottite, gases which closely resembled those in the Martian atmosphere as analyzed by Viking. These trapped gases provided direct evidence for a Martian origin. In 2000, an article by Treiman, Gleason and Bogard gave a survey of all the arguments used to conclude the SNC meteorites (of which 14 had been found at the time) were from Mars. They wrote, "There seems little likelihood that the SNCs are not from Mars. If they were from another planetary body, it would have to be substantially identical to Mars as it now is understood."


Subdivision

As of April 25, 2018, 192 of the 207 Martian meteorites are divided into three rare groups of achondritic (stony)
meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...
s: ''shergottites'' (169), ''nakhlites'' (20), ''chassignites'' (3), and ones otherwise (15) (containing the orthopyroxenite (OPX) Allan Hills 84001, as well as 10 basaltic breccia meteorites). Consequently, Martian meteorites as a whole are sometimes referred to as the ''SNC group''. They have
isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
ratios that are said to be consistent with each other and inconsistent with the Earth. The names derive from the location of where the first meteorite of their type was discovered.


Shergottites

Roughly three-quarters of all Martian meteorites can be classified as shergottites. They are named after the
Shergotty meteorite The Shergotty meteorite (Named after Sherghati) is the first example of the shergottite Martian meteorite family. It was a meteorite which fell to Earth at Sherghati, in the Gaya district, Bihar, India on 25 August 1865, and was retrieved by wit ...
, which fell at
Sherghati Sherghati is a town in the Gaya district in Bihar (formally Magadha ), India. The Morhar River surrounds it. A meteorite that came from Mars fell here on 25 August 1865; it is now kept in a London museum and is known as the Shergotty meteorit ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
in 1865. Shergottites are
igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock ...
s of
mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...
to
ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed ...
lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...
. They fall into three main groups, the
basaltic Basalt (; ) is an 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 surface of a rocky planet or moon. More than 90% of a ...
,
olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
-phyric (such as the
Tissint Tissint ( ber, ⵜⵉⵙⵉⵏⵜ, ar, تيسينت, also known as Agadir Tissinnt, Agadir Tissint, or Tissinnt) is a small town near Tata, Morocco in Tata Province in the Souss-Massa region of Morocco. It has a population of 9,927 as of 2004. ...
group found in Morocco in 2011) and Lherzolitic shergottites, based on their crystal size and mineral content. They can be categorised alternatively into three or four groups based on their
rare-earth element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silve ...
content. These two classification systems do not line up with each other, hinting at complex relationships between the various source rocks and magmas from which the shergottites formed. The shergottites appear to have crystallised as recently as 180 million years ago, which is a surprisingly young age considering how ancient the majority of the surface of Mars appears to be, and the small size of Mars itself. Because of this, some have advocated the idea that the shergottites are much older than this. This "Shergottite Age Paradox" remains unsolved and is still an area of active research and debate. It has been suggested the 3-million-year-old crater Mojave, 58.5 km in diameter, was a potential source of these meteorites. A paper published in 2021, however, disputes this, proposing instead the 28 km crater
Tooting Tooting is a district in South London, forming part of the London Borough of Wandsworth and partly in the London Borough of Merton. It is located south south-west of Charing Cross. History Tooting has been settled since pre- Saxon times ...
, or possibly the crater 09-000015 as the crater source of the depleted olivine-phyric shergottites ejected 1.1 Ma ago.


Nakhlites

Nakhlites are named after the first of them, the
Nakhla meteorite Nakhla is a Martian meteorite which fell in Egypt in 1911. It was the first meteorite reported from Egypt, the first one to suggest signs of aqueous processes on Mars, and the prototype for Nakhlite type of meteorites. History The Nakhla met ...
, which fell in
El-Nakhla Nakhla is a Martian meteorite which fell in Egypt in 1911. It was the first meteorite reported from Egypt, the first one to suggest signs of aqueous processes on Mars, and the prototype for Nakhlite type of meteorites. History The Nakhla met ...
,
Alexandria Alexandria ( or ; ar, ٱلْإِسْكَنْدَرِيَّةُ ; grc-gre, Αλεξάνδρεια, Alexándria) is the second largest city in Egypt, and the largest city on the Mediterranean coast. Founded in by Alexander the Great, Alexandria ...
,
Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediter ...
in 1911 and had an estimated weight of 10  kg. Nakhlites are
igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock ...
s that are rich in
augite Augite is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees. Characteristics Augite is a solid solution in the pyroxene group. ...
and were formed from
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 ...
ic
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...
from at least four eruptions, spanning around 90 million years, from 1416 ± 7 to 1322 ± 10 million years ago. They contain
augite Augite is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees. Characteristics Augite is a solid solution in the pyroxene group. ...
and
olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...
s. Their crystallization ages, compared to a crater count chronology of different regions on Mars, suggest the nakhlites formed on the large volcanic construct of either
Tharsis Tharsis () is a vast volcanic plateau centered near the equator in the western hemisphere of Mars. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Asc ...
,
Elysium Elysium (, ), otherwise known as the Elysian Fields ( grc, Ἠλύσιον πεδίον, ''Ēlýsion pedíon'') or Elysian Plains, is a conception of the afterlife that developed over time and was maintained by some Greek religious and philos ...
, or Syrtis Major Planum. It has been shown that the nakhlites were suffused with liquid water around 620 million years ago and that they were ejected from Mars around 10.75 million years ago by an asteroid impact. They fell to Earth within the last 10,000 years.


Chassignites

The first chassignite, the
Chassigny meteorite Chassigny is a Martian meteorite which fell on October 3, 1815, at approximately 8:00 am, in Chassigny, north-eastern France.Pistollet (1816) The circumstances of the Chassigny meteorite shower. Ann. Chim. Phys. (Paris) v. 1, pg 45-48. Chassigny i ...
, fell at Chassigny, Haute-Marne,
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
in 1815. There has been only one other chassignite recovered, named Northwest Africa (NWA) 2737. NWA 2737 was found in
Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...
or
Western Sahara Western Sahara ( '; ; ) is a disputed territory on the northwest coast and in the Maghreb region of North and West Africa. About 20% of the territory is controlled by the self-proclaimed Sahrawi Arab Democratic Republic (SADR), while the r ...
in August 2000 by meteorite hunters Bruno Fectay and Carine Bidaut, who gave it the temporary name "Diderot." It was shown by Beck ''et al.'' that its "
mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the proces ...
, major and trace element chemistry as well as
oxygen isotope There are three known stable isotopes of oxygen (8O): , , and . Radioactive isotopes ranging from to have also been characterized, all short-lived. The longest-lived radioisotope is with a half-life of , while the shortest-lived isotope is ...
s revealed an unambiguous Martian origin and strong affinities with Chassigny."


Ungrouped meteorites

Among these, the famous specimen
Allan Hills 84001 Allan Hills 84001 (ALH84001) is a fragment of a Martian meteorite that was found in the Allan Hills in Antarctica on December 27, 1984, by a team of American meteorite hunters from the ANSMET project. Like other members of the shergottite–nakhl ...
has a different rock type from other Martian meteorites: it is an orthopyroxenite (an igneous rock dominantly composed of orthopyroxene). For this reason it is classified within its own group, the "OPX Martian meteorites". This meteorite received much attention after an electron microscope revealed structures that were considered to be the
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
ized remains of
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
-like
life Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energ ...
forms. , scientific consensus was that the
microfossils A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...
were not indicative of Martian life, but of contamination by earthly
biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...
s. ALH 84001 is as old as the basaltic and intermediate shergottite groups i.e., 4.1 billion years old. In March 2004 it was suggested that the unique
Kaidun meteorite Kaidun is a meteorite that fell on 3 December 1980 on a Soviet military base near what is now Al-Khuraybah in Yemen. A fireball was observed travelling from the northwest to the southeast, and a single stone weighing about was recovered from a s ...
, which landed in
Yemen Yemen (; ar, ٱلْيَمَن, al-Yaman), officially the Republic of Yemen,, ) is a country in Western Asia. It is situated on the southern end of the Arabian Peninsula, and borders Saudi Arabia to the Saudi Arabia–Yemen border, north and ...
on December 3, 1980, may have originated on the Martian moon of Phobos. Because Phobos has similarities to
C-type asteroid C-type (carbonaceous) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...
s and because the Kaidun meteorite is a
carbonaceous chondrite Carbonaceous chondrites or C chondrites are a class of chondritic meteorites comprising at least 8 known groups and many ungrouped meteorites. They include some of the most primitive known meteorites. The C chondrites represent only a small prop ...
, Kaidun is not a Martian meteorite in the strict sense. However, it may contain small fragments of material from the Martian surface. The Martian meteorite
NWA 7034 Northwest Africa 7034 is a Martian meteorite believed to be the second oldest yet discovered.Associated Press (January 4, 2013)Mars meteorite 'Black Beauty' contains most water of any found on Earth, say scientists.''The Guardian'' It is estimated ...
(nicknamed "Black Beauty"), found in the
Sahara desert , photo = Sahara real color.jpg , photo_caption = The Sahara taken by Apollo 17 astronauts, 1972 , map = , map_image = , location = , country = , country1 = , ...
during 2011, has ten times the
water content Water content or moisture content is the quantity of water contained in a material, such as soil (called soil moisture), rock, ceramics, crops, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as ...
of other Mars meteorites found on Earth. The meteorite contains components as old as 4.42 ± 0.07 Ga (billion years), and was heated during the Amazonian geologic period on Mars. A meteorite that fell in 1986 in Dayanpo, China contained a magnesium silicate mineral called " Elgoresyte", a mineral not found on Earth.


Origin

The majority of SNC meteorites are quite young compared to most other meteorites and seem to imply that
volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...
activity was present on Mars only a few hundred million years ago. The young formation ages of Martian meteorites was one of the early recognized characteristics that suggested their origin from a planetary body such as Mars. Among Martian meteorites, only ALH 84001 and NWA 7034 have radiometric ages older than about 1400 Ma (Ma = million years). All nakhlites, as well as Chassigny and NWA 2737, give similar if not identical formation ages around 1300 Ma, as determined by various radiometric dating techniques. Formation ages determined for many shergottites are variable and much younger, mostly ~150–575 Ma. The chronological history of shergottites is not totally understood, and a few scientists have suggested that some may actually have formed prior to the times given by their radiometric ages, a suggestion not accepted by most scientists. Formation ages of SNC meteorites are often linked to their cosmic-ray exposure (CRE) ages, as measured from the nuclear products of interactions of the meteorite in space with energetic
cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
particles. Thus, all measured nakhlites give essentially identical CRE ages of approximately 11 Ma, which when combined with their possible identical formation ages indicates ejection of nakhlites into space from a single location on Mars by a single impact event. Some of the shergottites also seem to form distinct groups according to their CRE ages and formation ages, again indicating ejection of several different shergottites from Mars by a single impact. However, CRE ages of shergottites vary considerably (~0.5–19 Ma), and several impact events are required to eject all the known shergottites. It had been asserted that there are no large young craters on Mars that are candidates as sources for the Martian meteorites, but subsequent studies claimed to have a likely source for ALH 84001 and a possible source for other shergottites. In a 2014 paper, several researchers claimed that all shergottites meteorites come from the Mojave Crater on Mars.


Age estimates based on cosmic ray exposure

The amount of time spent in transit from Mars to Earth can be estimated by measurements of the effect of cosmic radiation on the meteorites, particularly on isotope ratios of
noble gas The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ...
es. The meteorites cluster in families that seem to correspond to distinct impact events on Mars. It is thought, therefore, that the meteorites all originate in relatively few impacts every few million years on Mars. The impactors would be kilometers in diameter and the craters they form on Mars tens of kilometers in diameter. Models of impacts on Mars are consistent with these findings.O. Eugster, G. F. Herzog, K. Marti, M. W. Caffe
Irradiation Records, Cosmic-Ray Exposure Ages, and Transfer Times of Meteorites, see section 4.5 Martian Meteorites
LPI, 2006
Ages since impact determined so far include


Possible evidence of life

Several Martian meteorites have been found to contain what some think is evidence for fossilized Martian life forms. The most significant of these is a meteorite found in the
Allan Hills The Allan Hills are a group of hills at the end of the Transantarctic Mountains System, located in Oates Land and Victoria Land regions of Antarctica. They are mainly ice free and about long, lying just north-west of the Coombs Hills near th ...
of
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
( ALH 84001). Ejection from Mars seems to have taken place about 16 million years ago. Arrival on Earth was about 13 000 years ago. Cracks in the rock appear to have filled with carbonate materials (implying groundwater was present) between 4 and 3.6 billion-years-ago. Evidence of
polycyclic aromatic hydrocarbons A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. P ...
(PAHs) have been identified with the levels increasing away from the surface. Other Antarctic meteorites do not contain PAHs. Earthly contamination should presumably be highest at the surface. Several minerals in the crack fill are deposited in phases, specifically,
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
deposited as
magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...
, that are claimed to be typical of biodepositation on Earth. There are also small ovoid and tubular structures that might be
nanobacteria ''Nanobacterium'' ( , pl. ''nanobacteria'' ) is the unit or member name of a former proposed class of living organisms, specifically cell-walled microorganisms, now discredited, with a size much smaller than the generally accepted lower limit ...
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s in carbonate material in crack fills (investigators McKay, Gibson, Thomas-Keprta, Zare).
Micropaleontologist Micropaleontology (American spelling; spelled micropalaeontology in European usage) is the branch of paleontology ( palaeontology) that studies microfossils, or fossils that require the use of a microscope to see the organism, its morphology and i ...
Schopf, who described several important terrestrial bacterial assemblages, examined ALH 84001 and opined that the structures are too small to be Earthly bacteria and don't look especially like lifeforms to him. The size of the objects is consistent with Earthly "
nanobacteria ''Nanobacterium'' ( , pl. ''nanobacteria'' ) is the unit or member name of a former proposed class of living organisms, specifically cell-walled microorganisms, now discredited, with a size much smaller than the generally accepted lower limit ...
", but the existence of nanobacteria itself is controversial. Many studies disputed the validity of the fossils. For example, it was found that most of the organic matter in the meteorite was of terrestrial origin. But, a recent study suggests that
magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...
in the meteorite could have been produced by Martian microbes. The study, published in the journal of the Geochemical and Meteoritic Society, used more advanced high resolution electron microscopy than was possible in 1996. A serious difficulty with the claims for a biogenic origin of the magnetites is that the majority of them exhibit topotactic crystallographic relationships with the host carbonates (i.e., there are 3D orientation relationships between the magnetite and carbonate lattices), which is strongly indicative that the magnetites have grown in-situ by a physico-chemical mechanism. While water is no indication of life, many of the meteorites found on Earth have shown water, including NWA 7034 which formed during the Amazonian period of Martian geological history. Other signs of surface liquid
water on Mars 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 f ...
(such as
recurring slope lineae Seasonal flows on warm Martian slopes (also called recurring slope lineae, recurrent slope lineae and RSL) are thought to be salty water flows occurring during the warmest months on Mars, or alternatively, dry grains that "flow" downslope of at le ...
) are a topic of debate among planetary scientists, but generally consistent with the earlier evidence provided by Martian meteorites. Any liquid water present is likely too minimal to support life.


See also

*
Colin Pillinger Colin Trevor Pillinger, (; 9 May 1943 – 7 May 2014) was an English planetary scientist. He was a founding member of the Planetary and Space Sciences Research Institute at Open University in Milton Keynes, he was also the principal inves ...
*
Glossary of meteoritics This is a glossary of terms used in meteoritics, the science of meteorites. # * 2 Pallas – an asteroid from the asteroid belt and one of the likely parent bodies of the CR meteorites. * 4 Vesta – second-largest asteroid in the asteroid b ...
* List of Martian meteorites (on Earth) *
List of meteorites on Mars This is an alphabetical list of named rocks (and meteorites) found on Mars, by mission. This list is a sampling of rocks viewed, and is not an exhaustive listing. A more complete listing may be found on the various NASA mission web sites. This lis ...
*
Lithopanspermia Panspermia () is the hypothesis, first proposed in the 5th century BCE by the Greek philosopher Anaxagoras, that life exists throughout the Universe, distributed by space dust, meteoroids, asteroids, comets, and planetoids, as well as by spacecr ...
, which includes the speculation that life on Earth may have arrived as microbes on Martian meteorites *
Mars sample-return mission A Mars sample-return (MSR) mission is a proposed mission to collect rock and dust samples on Mars and return them to Earth. Such a mission would allow more extensive analysis than that allowed by onboard sensors. The three most recent concept ...


References

;General *


External links


List of Martian Meteorites

Mars Meteorite Home Page (JPL)






{{DEFAULTSORT:Martian Meteorite
Meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...