Editing Martian meteorite (section)

==Subdivision==
[[File:Martian meteorites subdivision.svg|thumbnail|right|The Martian meteorites are divided into three groups (orange) and two grouplets (yellow). SHE = [[Shergottite]], NAK = [[Nakhlite]], CHA = [[Chassignite]], OPX = Orthopyroxenite ([[ALH 84001]]), BBR = Basaltic Breccia ([[NWA 7034]]).]]

As of April 25, 2018, 192 of the 207 Martian meteorites are divided into three rare groups of [[Achondrite|achondritic]] (stony) [[meteorite]]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).<ref name=metbull/> Consequently, Martian meteorites as a whole are sometimes referred to as the ''SNC group'' (pronounced {{IPAc-en|s|n|ɪ|k|}}).<ref>{{cite book |last1=Murdin |first1=P |title=Encyclopedia of Astronomy & Astrophysics |publisher=CRC Press |isbn=9781000523034 |chapter=SNC Meteorite |date=January 2001 |quote=The letters SNC (pronounced `snick') stand for the three main classes: shergottites, nakhlites and chassignites.}}</ref> They have [[isotope]] ratios that are consistent with each other and inconsistent with a terrestrial origin. 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]], which fell at [[Sherghati]], [[India]] in 1865.<ref>[http://www2.jpl.nasa.gov/snc/shergotty.html Shergotty Meteorite - JPL, NASA]</ref> Shergottites are [[igneous rock]]s of [[mafic]] to [[ultramafic]] [[lithology]]. They fall into three main groups, the [[basaltic]], [[olivine]]-phyric (such as the [[Tissint]] group found in Morocco in 2011<ref>{{Cite web | url=http://www.space.com/18014-mars-meteorites-black-glass.html | title=Meteorite's Black Glass May Reveal Secrets of Mars| website=[[Space.com]]| date=11 October 2012 |first=Charles Q. |last=Choi}}</ref><ref>{{cite news|last=Morin|first=Monte|title=An unusually pristine piece of Mars|url=https://www.latimes.com/world/middleeast/la-xpm-2012-oct-12-la-sci-martian-meteorite-20121010-story.html|newspaper=Los Angeles Times|date=October 12, 2012}}</ref>) and [[lherzolite|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]] content.<ref name="Bridges Warren 2006 pp. 229–251">{{cite journal | last1=Bridges | first1=J.C. | last2=Warren | first2=P.H. | title=The SNC meteorites: basaltic igneous processes on Mars | journal=Journal of the Geological Society | publisher=Geological Society of London | volume=163 | issue=2 | year=2006 | issn=0016-7649 | doi=10.1144/0016-764904-501 | pages=229–251| bibcode=2006JGSoc.163..229B | s2cid=6815557 | url=http://oro.open.ac.uk/71/1/Bridges-Warren-revised._Jour_of_geo_soc_spec_iss.pdf }}</ref> 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.
[[File:NWA 6963 full slice.jpg|thumb|left|NWA 6963,<ref>{{Cite web |url=http://www.lpi.usra.edu/meteor/metbull.php?code=54565 |title=Northwest Africa 6963 (NWA 6963)}}</ref> a shergottite found in Morocco, September 2011.]] 
The shergottites appear to have crystallised as recently as 180 million years ago,<ref name="Nyquist 2001 105–164"/> 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.<ref>{{cite journal|title= Martian meteorite chronology and the evolution of the interior of Mars|journal=Earth and Planetary Science Letters|volume=280|issue=1–4|pages=285–295|doi=10.1016/j.epsl.2009.01.042|year=2009|last1=Bouvier|first1=Audrey|last2=Blichert-Toft|first2=Janne|author2-link=Janne Blichert-Toft|last3=Albarède|first3=Francis|bibcode=2009E&PSL.280..285B}}</ref> 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 (crater)|Mojave]], 58.5&nbsp;km in diameter, was a potential source of these meteorites.<ref name="Werner2014">{{Cite journal | doi = 10.1126/science.1247282| title = The Source Crater of Martian Shergottite Meteorites| date = 2014-03-06| last1 = Werner | first1 = S. C.|author1-link= Stephanie C. Werner | journal = Science| volume = 343| issue = 6177| pages = 1343–6| last2 = Ody | first2 = A. | last3 = Poulet | first3 = F. | pmid=24603150| bibcode = 2014Sci...343.1343W| s2cid = 206553043| doi-access = free}}</ref> A paper published in 2021, however, disputes this, proposing instead the 28 km crater [[Tooting (crater)|Tooting]], or possibly the crater [[09-000015]] as the crater source of the depleted olivine-phyric shergottites ejected 1.1 Ma ago.<ref>{{Cite journal|last1=Lagain|first1=A.|last2=Benedix|first2=G. K.|last3=Servis|first3=K.|last4=Baratoux|first4=D.|last5=Doucet|first5=L. S.|last6=Rajšic|first6=A.|last7=Devillepoix|first7=H. a. R.|last8=Bland|first8=P. A.|last9=Towner|first9=M. C.|last10=Sansom|first10=E. K.|last11=Miljković|first11=K.|date=2021-11-03|title=The Tharsis mantle source of depleted shergottites revealed by 90 million impact craters|journal=Nature Communications|language=en|volume=12|issue=1|pages=6352|doi=10.1038/s41467-021-26648-3|pmid=34732704|pmc=8566585|bibcode=2021NatCo..12.6352L |issn=2041-1723}}</ref><ref>{{Cite web|last=Gough|first=Evan|date=2021-11-08|title=We Now Know Exactly Which Crater the Martian Meteorites Came From|url=https://www.universetoday.com/153207/we-now-know-exactly-which-crater-the-martian-meteorites-came-from/|access-date=2021-11-15|website=Universe Today|language=en-US}}</ref>

===Nakhlites===
[[File:Nakhla meteorite.jpg|thumb|200px|[[Nakhla meteorite]]'s two sides and its inner surfaces after breaking it]]
{{Main|Nakhlite}}
Nakhlites are named after the first of them, the [[Nakhla meteorite]], which fell in [[El-Nakhla]], [[Alexandria]], [[Egypt]] in 1911 and had an estimated weight of 10&nbsp;[[gram|kg]].

Nakhlites are [[igneous rock]]s that are rich in [[augite]] and were formed from [[basalt]]ic [[magma]] from at least four eruptions, spanning around 90 million years, from 1416 ± 7 to 1322 ± 10 million years ago.<ref name=":0">{{Cite journal|last1=Cohen|first1=Benjamin E.|last2=Mark|first2=Darren F.|last3=Cassata|first3=William S.|last4=Lee|first4=Martin R.|last5=Tomkinson|first5=Tim|last6=Smith|first6=Caroline L.|date=2017-10-03|title=Taking the pulse of Mars via dating of a plume-fed volcano|journal=Nature Communications|language=En|volume=8|issue=1|pages=640|doi=10.1038/s41467-017-00513-8|pmid=28974682|pmc=5626741|issn=2041-1723|bibcode=2017NatCo...8..640C}}</ref> They contain [[augite]] and [[olivine]] [[crystal]]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]], [[Elysium Planitia|Elysium]], or [[Syrtis Major Planum]].<ref name=Nakhlites>{{cite journal |author=Treiman, A.H. |url=https://www.lpi.usra.edu/science/treiman/nakhlite_rev.pdf |title=The nakhlite meteorites: Augite-rich igneous rocks from Mars |volume=65 |issue=3 |journal=Chemie der Erde |pages=203–270 |year=2005 |access-date=July 30, 2011|bibcode=2005ChEG...65..203T |doi=10.1016/j.chemer.2005.01.004 }}</ref>

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.<ref name=Nakhlites/>

===Chassignites===
The first chassignite, the [[Chassigny (meteorite)|Chassigny meteorite]], fell at [[Chassigny, Haute-Marne]], [[France]] in 1815. There has been only one other chassignite recovered, named Northwest Africa (NWA) 2737. NWA 2737 was found in [[Morocco]] or [[Western Sahara]] 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.''<ref>{{cite conference |author=Beck, P. |display-authors=etal |url=http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1326.pdf |title=The Diderot meteorite: The second chassignite |conference=36th Annual Lunar and Planetary Science Conference |date=March 14–18, 2005 |location=League City, Texas |id=abstract no.1326. |access-date=September 8, 2006 }}</ref> that its "[[mineralogy]], major and trace element chemistry as well as [[Isotopes of oxygen|oxygen isotope]]s revealed an unambiguous Martian origin and strong affinities with Chassigny."

===Ungrouped meteorites===
[[File:ALH84001.jpg|thumb|right|200px|[[Allan Hills 84001]] (ALH 84001)]]
Among these, the famous specimen [[Allan Hills 84001]] has a different rock type from other Martian meteorites: it is an [[pyroxenite|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]]ized remains of [[bacteria]]-like [[life]]forms. {{As of|2005}}, scientific consensus was that the [[Microfossil|microfossils]] were not indicative of Martian life, but of contamination by earthly [[biofilm]]s. ALH 84001 is as old as the basaltic and intermediate shergottite groups{{snd}} i.e., 4.1 billion years old.{{Citation needed|reason=No supporting information referenced|date=April 2017}}

In March 2004 it was suggested that the unique [[Kaidun meteorite]], which landed in [[Yemen]] on December 3, 1980,<ref>[https://www.lpi.usra.edu/meteor/metbull.php?code=12228 Meteoritical Bulletin Database]</ref> may have originated on the Martian moon of [[Phobos (moon)|Phobos]].<ref>{{cite journal|author=Zolensky, M. and Ivanov A.|title=The Kaidun Microbreccia Meteorite: A Harvest from the Inner and Outer Asteroid Belt|journal= Geochemistry|volume=63|issue=3|pages=185–246|date= 2003|doi=10.1078/0009-2819-00038|bibcode=2003ChEG...63..185Z |url=https://zenodo.org/record/1236062}}</ref> Because Phobos has similarities to [[C-type asteroid]]s and because the Kaidun meteorite is a [[carbonaceous chondrite]], 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]] (nicknamed "Black Beauty"), found in the [[Sahara desert]] during 2011, has ten times the [[Asteroidal water|water content]] of other Mars meteorites found on Earth.<ref name="NASA-20130103" /> The meteorite contains components as old as 4.42 ± 0.07 Ga (billion years),<ref>{{Cite journal|last1=Nyquist|first1=Laurence E.|last2=Shih|first2=Chi-Yu|last3=McCubbin|first3=Francis M.|last4=Santos|first4=Alison R.|last5=Shearer|first5=Charles K.|last6=Peng|first6=Zhan X.|last7=Burger|first7=Paul V.|last8=Agee|first8=Carl B.|date=2016-02-17|title=Rb-Sr and Sm-Nd isotopic and REE studies of igneous components in the bulk matrix domain of Martian breccia Northwest Africa 7034|journal=Meteoritics & Planetary Science|language=en|volume=51|issue=3|pages=483–498|doi=10.1111/maps.12606|issn=1086-9379|bibcode=2016M&PS...51..483N|s2cid=131565237 |doi-access=free}}</ref> and was heated during the [[Geological history of Mars#Crater density timescale|Amazonian geologic period]] on Mars.<ref>{{Cite journal|last1=Cassata|first1=William S.|last2=Cohen|first2=Benjamin E.|last3=Mark|first3=Darren F.|last4=Trappitsch|first4=Reto|last5=Crow|first5=Carolyn A.|last6=Wimpenny|first6=Joshua|last7=Lee|first7=Martin R.|last8=Smith|first8=Caroline L.|date=2018-05-01|title=Chronology of martian breccia NWA 7034 and the formation of the martian crustal dichotomy|journal=Science Advances|language=en|volume=4|issue=5|pages=eaap8306|doi=10.1126/sciadv.aap8306|pmid=29806017|pmc=5966191|issn=2375-2548|bibcode=2018SciA....4.8306C}}</ref>

A meteorite that fell in 1986 in Dayanpo, China contained a magnesium silicate mineral called "[[Elgoresyite|Elgoresyte]]", a mineral not found on Earth.<ref>{{Cite web|title=A Mineral Unknown On Earth Could Be The Most Abundant Mineral On Mars|url=https://www.geologyin.com/2021/08/a-mineral-unknown-on-earth-could-be.html |date=2021-08-09 |work=Geology In |access-date=2021-08-18|language=en}}</ref>