Martian meteorites: How Did a Piece of Mars Get to Earth?

Sabaeus sinus region of mars

The 1970’s Viking mission to Mars provided much of our information about the geology and weather of the red planet. Viking had two orbiters which remotely mapped the surface of Mars, and two landers which analyzed rocks and soils. The Viking mission did not return a Mars rock sample to Earth. Further crucial information about Mars comes from an unexpected source – meteorites that arrived on Earth unaided by technology. They are at least one hundred forty unusual martian meteorites that are almost certainly pieces of Mars blasted off the planet by meteoroid impact.

Why are they from Mars?

The one hundred forty meteorites are unusual igneous meteorites (SNC achondrites named Shergotty, Nakhla, Chassigny are type examples). Most martian meteorites are 1.3 billion years old or less, much younger than typical igneous meteorites from asteroids which are 4.5 billion years old. They also have higher contents of volatiles than igneous meteorites. The conclusive evidence that the SNC meteorites originated on Mars comes from the measurement of gases trapped in one meteorite’s interior. The trapped gases match those that Viking measured in the martian atmosphere.

The martian meteorites represent five different types of igneous rocks, ranging from simple plagioclase-pyroxene basalts to almost monomineralic cumulates of pyroxene or olivine. The meteorites and their rock types are listed in Table 1. Photographs of whole rocks and thin sections of a basalt and a cumulate are illustrated below. All of the meteorites solidified near the martian surface by crystallization from a cooling magma. Some of the shergottite basalts have close to magma compositions, while the other martian meteorites are dominated by accumulation of olivine and/or pyroxene. None of the martian meteorites are surface samples in that they have not been exposed to extensive weathering or irradiation by cosmic rays. The martian soil analyzed by Viking appears to be a weathered basalt which could have been of shergottite composition.

Martian Meteorites List (142)

An up-to-date List of Martian Meteorites created by Dr. Tony Irving of the University of Washington, sponsored by the International Meteorite Collectors Association, IMCA Inc. The number of terrestrially-unpaired meteorites stated here is a best estimate based on available information and is subject to change. It is very difficult to properly assess the pairing relationships among the most common Enriched Mafic Shergottites, so the actual number of unpaired specimens may be slightly lower than stated.

NameLocationYearOriginal mass (g)Classification type
ChassignyChassigny, France (October 3)1815~4,000Chassignite
(Dunite)
ShergottyShergotty, India (August 25)1865~5,000Shergottite
(Enriched Mafic Diabasic)
NakhlaNakhla, Egypt (June 28)1911~9,900Nakhlite
(Augite-Olivine-Rich Cumulate)
LafayetteIllinois(?) & Purdue Univ., USA1931~800Nakhlite
(Augite-Olivine-Rich Cumulate)
Governador ValadaresGovernador Valadares, Brazil1958158Nakhlite
(Augite-Olivine-Rich Cumulate)
ZagamiZagami, Nigeria (October 3)1962~18,000Shergottite
(Enriched Mafic Intersertal)
ALHA 77005Allan Hills, Antarctica1977482.5Shergottite
(Intermediate Ultramafic Poikilitic)
Yamato 793605Yamato Mountains, Antarctica1979~16Shergottite
(Intermediate Ultramafic Poikilitic)
EETA 79001 A & BElephant Moraine, Antarctica19807942Shergottite
(Intermediate Permafic Olivine-Phyric & Mafic)
Los AngelesMojave Desert via Los Angeles, USA~1980(?) [1999]452.6 / 245.4Shergottite
(Enriched Mafic Diabasic)
ALH 84001Allan Hills, Antarctica19841939.9Orthopyroxenite
(Enriched Ultramafic Phaneritic)
LEW 88516Lewis Cliff, Antarctica198813.2Shergottite
(Intermediate Ultramafic Poikilitic)
QUE 94201Queen Alexandra Range, Antarctica199412Shergottite
(Depleted Mafic Diabasic)
Dar al Gani 476 / 489 / 670 / 735/ 876 / 975 / 1037 / 1051Dar al Gani, Libya1996-20002,015 / 2,146 / 1,619 / 588 / 6.2 / 27.6 / 4,012 / 40.1Shergottite
(Depleted Permafic Olivine-Orthopyroxene-Phyric)
Yamato 980459 / 980497Yamato Mountains, Antarctica199882.5 / 8.7Shergottite
(Depleted Permafic Olivine-Phyric)
Yamato 984028 / 000027 / 000047 / 000097Yamato Mountains, Antarctica1998-200012.3 / 9.7 / 5.3 / 24.5Shergottite
(Intermediate Ultramafic Poikilitic)
YA 1075Yamato Mountains, Antarctica199955Shergottite
(Intermediate Ultramafic Poikilitic)
Sayh al Uhaymir 005 / 008 / 051 / 060 / 090 / 094 / 120 / 125 / 130 / 150 / 587Sayh al Uhaymir, Oman1999-20141,344 / 8,579 / 436 /
42 / 95 / 223 / 75 / 32 / 279 / 108 / 4.7
Shergottite
(Depleted Permafic Olivine-Phyric)
Dhofar 019 / Dhofar 1668 / Dhofar 1674Dhofar, Oman2000-20101,056 / 6.1 / 49.2Shergottite
(Depleted Permafic Olivine-Phyric)
GRV 99027Grove Mountains, Antarctica200010Shergottite
(Intermediate Ultramafic Poikilitic)
Dhofar 378 / [Unnamed 1]Dhofar, Oman2000-200115 / 209.1Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 480 / 1460Morocco2000-200128 / 70Shergottite
(Intermediate Mafic Diabasic)
Yamato 000593 / 000749 / 000802Yamato Mountains, Antarctica200013,713 / 1,283 / 22Nakhlite
(Augite-Olivine-Rich Cumulate)
Northwest Africa 817Morocco2000104Nakhlite
(Augite-Olivine-Rich Cumulate)
Northwest Africa 2737Morocco or Algeria2000611Chassignite
(Dunite)
Northwest Africa 1669Morocco200135.9Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 1950 / 7721Atlas Mountains, Morocco2001-2012797 / 32Shergottite
(Intermediate Permafic Poikilitic)
Northwest Africa 856Morocco2001320Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 1068 / 1110 / 1183 / 1775 / 2373 / 2969Maarir, Morocco2001-2004577 / 118 / 140 / 25 / 18 / 12Shergottite
(Enriched Permafic Olivine-Phyric)
Northwest Africa 998Algeria2001456Nakhlite
(Augite-Olivine-Rich Cumulate)
Northwest Africa 4797Missour, Morocco200115Shergottite
(Intermediate Ultramafic Poikilitic)
[Unnamed 2]Northwest Africa2001~56Shergottite
(?Enriched Permafic Poikilitic)
Northwest Africa 1195Safsaf, Morocco / Algeria2002315Shergottite
(Depleted Permafic Olivine-Orthopyroxene-Phyric)
GRV 020090Grove Mountains, Antarctica20027.54Shergottite
(Intermediate Ultramafic Poikilitic)
Northwest Africa 2046Lakhbi, Algeria200363Shergottite
(Depleted Permafic Olivine-Orthopyroxene-Phyric)
MIL 03346 / 090030 / 090032 / 090136Miller Range, Antarctica2003-2009715 / 453 / 532 / 171Nakhlite
(Augite-Olivine-Rich Cumulate)
Northwest Africa 5029Morocco200314.67Shergottite
(Intermediate Mafic Diabasic)
Northwest Africa 3171Algeria2004506Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 2626Algeria200431.1Shergottite
(Depleted Permafic Olivine-Orthopyroxene-Phyric)
Northwest Africa 2646Algeria or Morocco200430.7Shergottite
(Intermediate Permafic Poikilitic Olivine Meladiabasic)
RBT 04261 / 04262Roberts Massif, Antarctica200478.8 / 204.6Shergottite
(Enriched Permafic Poikilitic)
Northwest Africa 2975 / 2986 / 2987 / 4766 / 4783 / 4857 / 4864 / 4878/ 4880 / 4930 / 5140 / 5214/ 5219 / 5313 / 5366 / 7182 / 7890 / 8116 / 10068 / 10450 / 11804Tanezrouft, Algeria2005-201770.1 / 201 / 82 / 290 / 120 / 24 / 94 / 130 / 81.6 / 117.5 / 7.5 / 50.7 / 60 / 5.3 / 39.6 / 17 / 5.1 / 0.5 / 616 /19.9 / 34.0Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 4222Algeria or Morocco200616.55Shergottite
(Depleted Permafic Olivine-Phyric)
Northwest Africa 4468Southern Morocco2006675Shergottite
(Enriched Permafic Poikilitic)
Northwest Africa 4480Algeria or Morocco200613Shergottite
(‘Intermediate’ Mafic Intersertal)
Northwest Africa 4527 / 4925Algeria200610.06 / 282.3Shergottite
(Depleted Permafic Olivine-Phyric)
Northwest Africa 5718Algeria or Morocco200690.5Shergottite
(Enriched Mafic Intersertal)
LAR 06319 / 12011Larkman Nunatak, Antarctica2007-201278.6 / 701.2Shergottite
(Enriched Permafic Olivine-Phyric)
Northwest Africa 2990 / 5960 / 6234 / 6710 / 10170Mauritania2007-2009363 / 147 / 55.7 / 74.4 / 307Shergottite
(Intermediate Permafic Olivine-Phyric)
Northwest Africa 2800Algeria or Morocco2007686Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 5790 / 6148Mauritania2008-2009145 / 270Nakhlite
(Augite-Olivine-Rich Cumulate)
Northwest Africa 5298Bir Gandouz, Morocco2008445Shergottite
(Enriched Mafic Diabasic)
Jiddat al Harasis 479Oman2008553Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 5789Morocco200949Shergottite
(Depleted Permafic Olivine-Phyric)
Northwest Africa 5990Hamada du Drâa, Morocco200959Shergottite
(Depleted Permafic Diabasic)
Ksar Ghilane 002Quibili, Tunisia2010538Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 6162Lbirat, Morocco201089Shergottite
(Depleted Permafic Olivine-Phyric)
Northwest Africa 6342Algeria201072.2Shergottite
(Intermediate Ultramafic Poikilitic)
Northwest Africa 6963 / 7258 / 11431Fej Arrih, Morocco to northern Mauritania2011-2017>8,000 / 310 / 524Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 7032 / 7272(?)Algeria201185 / 58.7Shergottite
(Depleted Permafic Microgabbroic)
Northwest Africa 7034 / 7475 / 7533 / 7906 / 7907 / 8114 / 8171 / 8674 / 10922 / Rabt Sbayta 003 / 11220 / 11522 / [Unnamed 24] / 11896 / 11921 / Rabt Sbayta 010Rabt Sbayta, Morocco2011-2017320 / 80.2 / 84 / 47.7 / 29.9 / 1.9 / 81.9 / 12 / 182 / 20.57 / 36.63 / 3.2 / 674 / 14 / 7.7 / 6.1Polymict Regolith Breccia (Mafic)
Northwest Africa 7042Morocco20113033Shergottite
(Intermediate Permafic Intersertal)
TissintTanzrou, Morocco (July 18)2011>12,000Shergottite
(Depleted Permafic Olivine-Phyric)
Northwest Africa 7257Morocco2011180Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 7320Southern Morocco201152Shergottite
(Enriched Mafic Gabbroic)
Northwest Africa 7397 / 7387 / 7755 / 7937 / 8161Chwichiya, Morocco2012-20132,130 / 392 / 30 / 152.9 / 216Shergottite
(Enriched Permafic Poikilitic)
Northwest Africa 7500Taoudenni, Mali20122040Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 7635Dahkla, Morocco2012195.8Shergottite
(Depleted Mafic Olivine-Plagioclase-Phyric)
LAR 12095 / 12240Larkman Nunatak, Antarctica2012133.1 / 57.6Shergottite
(Depleted Permafic Olivine-Phyric)
Northwest Africa 7944Al Mahbas, Morocco2013815Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 8159(?)Morocco2013149.4Shergottite
(Depleted Mafic Aphyric / Augite-Rich)
Northwest Africa 12412(?)2013346Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 8637Near Chwichiya, Morocco20144.2Shergottite
(Enriched Permafic Microgabbroic)
Northwest Africa 8656 / 8657 / 10016 / 10375 / 10441 / 10593 / 10628 / 10703 / 10728 / 10994 / 11044 / 11288 / 11668 / 11746 / Tindouf 002Tindouf, Algeria20141,655.8 / 233.6 / 11 / 30 / 238.8 / 279 / 24.1 / 111 / 137 / 9.4 / 104.7 / 406.6 / 20.0 / 9.4 / 78.2Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 8653 / [Unnamed 3]Mauritania2014214 / 119Shergottite
(?Enriched Mafic Intersertal)
Jrifiya (Sueilila 002)Jrifiya, Morocco20143694Shergottite
(Depleted Permafic Olivine-Phyric)
Northwest Africa 8679Morocco2014285Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 8686Morocco2014376Shergottite
(Enriched Permafic Olivine-Phyric)
Northwest Africa 8694Morocco201454.8Chassignite
(Dunite)
Northwest Africa 8705(?)Morocco20146.2Shergottite
(Intermediate Permafic Olivine-Phyric)
Northwest Africa 10153 / 10645 / 10659 / 10720 / 11013Algeria or Mauritania2014119 / 12 / 7.2 / 1015 / 20.81Nakhlite
(Augite-Olivine-Rich Cumulate)
Northwest Africa 10281 / (?)10299Morocco2014765 / 339Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 10134(?)Morocco201425.4Shergottite
(Enriched Mafic Intersertal)
Northwest Africa 10169 / (?)10344 / (?)12002Morocco201522 / 20 / 5Shergottite
(Enriched Permafic Poikilitic)
Northwest Africa 10171Morocco201523.4Shergottite
(?Enriched Mafic Intersertal)
Northwest Africa 10416Mali2015964Shergottite
(Depleted Permafic Olivine-Phyric)
Yamato 002192 / 002712Yamato Mountains, Antarctica200032.1 / 72.9Shergottite
(?Enriched Mafic Diabasic)
Northwest Africa 10414(?)Morocco201539.8Shergottite
(?Enriched Mafic Pigeonite-Phyric)
Northwest Africa 10558(?)Morocco201514.3Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 10567Chwichiya, Morocco2015323Shergottite
(Intermediate Permafic Microgabbroic)
Northwest Africa 10618(?)Morocco201693.8Shergottite
(Enriched Permafic Poikilitic)
Northwest Africa 10697(?)Mauritania2016151Shergottite
(Intermediate Permafic Poikilitic)
Northwest Africa 10693Mauritania2016111Shergottite
(Depleted Permafic Olivine-Phyric)
Northwest Africa 10761Morocco2016473Shergottite
(Intermediate Mafic Gabbroic)
Northwest Africa 11251Morocco2015266Shergottite
(Enriched Permafic Diabasic)
Northwest Africa 10808Mauritania2016188Shergottite
(Enriched Permafic Poikilitic)
Northwest Africa 11065(?)Morocco201676.3Shergottite
(Intermediate Permafic Poikilitic)
Northwest Africa 10961Morocco20162220Shergottite
(Intermediate Ultramafic Poikilitic)
Northwest Africa 11214(?)Mauritania2016477Shergottite
(Intermediate Ultramafic Poikilitic)
[Unnamed 16](?)Mauritania2016148Shergottite
(?Depleted Permafic Olivine-Phyric)
Northwest Africa 11057(?)Mauritania20163660Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 11073(?)Mali2016247.7Shergottite
(Enriched Mafic Aphyric)
Northwest Africa 11043 / [Unnamed 19]Mali2016544 / 450Shergottite
(Intermediate ?Permafic Poikilitic)
Northwest Africa 11115(?)2016246.8Shergottite
(Enriched Permafic Olivine-Phyric)
Northwest Africa 11255Morocco20171099Shergottite
(Enriched Mafic Aphyric)
Northwest Africa 11300(?)201771.6Shergottite
(Intermediate Mafic Gabbroic)
Northwest Africa 11339Morocco2017161Shergottite
(Enriched Mafic Aphyric)
Northwest Africa 11261 / ?10818(?)Algeria or Mauritania2017114 / 166.2Shergottite
(Intermediate Ultramafic Poikilitic)
Northwest Africa 11509Mali2017500Shergottite
(‘Intermediate’ Permafic Olivine Gabbroic)
[Unnamed 25](?)2018460Shergottite
(?Intermediate ?Ultramafic ?Poikilitic)
Northwest Africa 11955Mauritania2018272Shergottite
(Enriched Permafic Gabbroic)
Northwest Africa 12210(?)2018151.4Shergottite
(Enriched Permafic Poikilitic)
Caleta el Cobre 022Chile2016474Nakhlite
(Augite-Olivine-Rich Cumulate)
Northwest Africa 12323(?)Mali or Niger2018447Shergottite
(Intermediate Mafic Gabbroic)
Asuka 12325Nansen Ice Field, Antarctica201228.02Shergottite
Ramlat Fasad 057Oman201613.1Shergottite
(?Intermediate Permafic Microgabbroic)
Northwest Africa 2424(?)201658Shergottite
(Intermediate Permafic Olivine-Phyric)
Northwest Africa 11866(?)Morocco201823.3Shergottite
(?Enriched Mafic Diabasic)
Northwest Africa 12262 / 12335 / 12522 / 12525 / 12550 / ?12594 / [Unnamed 37] / Ouargla 003 / [Unnamed 47] / 12908 / 12960 / 12965 / 13115 / 13187(?)Algeria2018-20193294 / 3970 / 1128 / 15 / 16.4 / 150 / 1860 / 68.4 / 2450 / 86 / 94 / 75.1 / 1524 / 1600Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 12269 / [Unnamed 48] / ?12919(?)Algeria20181679 / 320 / 7.5Shergottite
(Enriched Mafic Intersertal)
[Unnamed 33](?)2018~500Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 12241 / 12837Algeria20181150 / 4147Shergottite
(Intermediate ?Permafic Olivine Gabbroic Orthocumulate)
Northwest Africa 12418Morocco201831.8Shergottite
(Intermediate Permafic Poikilitic)
Northwest Africa 12450Morocco201814.2Shergottite
(Depleted Permafic Olivine-Phyric)
Northwest Africa 12536(?)Morocco201864.4Shergottite
(Intermediate Permafic Olivine-Phyric)
Northwest Africa 12564(?)Mauritania20181918Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 12392(?)2018502Shergottite
(?Enriched Mafic Diabasic / Augite-Poor)
[Unnamed 40](?)Mauritania2019~3000Shergottite
(Intermediate Mafic Aphyric)
Northwest Africa 12632(?)Mauritania201964.85Shergottite
(Enriched Mafic Gabbroic)
Northwest Africa 12542(?)Mauritania20181082Nakhlite
(Augite-Olivine-Rich Cumulate)
Swayyah 002Morocco20194523Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 12690(?)Niger20199095Shergottite
(?Enriched Mafic Diabasic)
Gadamis 001Libya20197000Shergottite
(Enriched Mafic Diabasic)
Northwest Africa 13179(?)Mauritania2019175Shergottite
(Depleted Ultramafic Olivine Microwebsteritic)
Rafsa 001Algeria2019127.6Shergottite
(Intermediate Permafic Olivine-Phyric)
Northwest Africa 13031(?)2019211Shergottite
(Intermediate Permafic Pyroxene-Phyric)
Northwest Africa 13204Morocco201976.8Shergottite
(?Enriched Mafic Diabasic)
Northwest Africa 13038(?)2019587Shergottite
(Intermediate Mafic Intersertal)
Northwest Africa 13227(?)20192300Shergottite
(?Intermediate Permafic Olivine Gabbroic)
[Unnamed 55](?)20193652Shergottite
(Intermediate Permafic Poikilitic)
[Unnamed 56]Libya2019244.5Shergottite
(Enriched Mafic Aphyric)
[Unnamed 57](?)201945Shergottite
(?Intermediate Ultramafic Poikilitic)
New EntryTBD20XX0Unknown

For a current list of classified specimens, click here

How did the martian meteorites get here?

Meteoroid impact is the only natural process capable of launching martian rocks to Earth. To be ejected from Mars a rock must reach the escape velocity of 5.4 km/sec, which is more than five times the muzzle velocity of a hunting rifle. An impact capable of ejecting the martian meteorites into space would have left a crater of 10-100 km. The meteorites spent several million years in space before landing at various sites on Earth.

Earth Science and Solar System Exploration Division, Johnson Space Center

Scientists think that martian meteorites found on Earth have been ejected from the red planet by asteroid impacts. Calculations suggest that there are two ways this can happen. First, an asteroid at least ten kilometers (six miles) wide could fall straight down to the martian surface. The impact crater left behind in this event would be round and at least a hundred kilometers wide.

It’s equally possible that a smaller asteroid, perhaps one kilometer in diameter, might be able to knock material free from Mars, if it approached the martian surface at a very low angle. In this case, the asteroid would swoop in more like an airplane landing than a rock falling straight down. Its impact crater would be elliptical and smaller, as small as ten kilometers wide.

Martian meteorites ALH84001 found in Allan Hills region of Antarctica

No one can say exactly what trajectory ALH84001 took when it spalled off the planet. Scientists will only say that it drifted among the planets of the inner solar system until it encountered Earth some 13,000 years ago. But, in light of the two possibilities suggested above, scientists now think they may know the place on Mars where ALH84001 originated. This is important because identification of the meteorite’s site of origin may have a bearing on future Mars missions.

Planetary scientist Nadine Barlow of the University of Central Florida led the search for the source crater. With the help of a comprehensive crater catalog that she had compiled while doing her graduate work at the University of Arizona in the mid-1980s, and taking into account a number of distinctive characteristics of the meteorite itself, Barlow was able to narrow the search to two possible source craters on Mars.

Because of its great age, the meteorite must have come from the most ancient of martian terrain. Because the meteorite was chipped off Mars only 16 million years ago – very recently on a geologic timescale – Barlow reasoned that the source crater must still exhibit young features, such as a sharp crater rim and an unweathered blanket of ejected material surrounding the crater.

Also, ALH84001 shows evidence of a shock event that preceded its ejection from Mars. In other words, while it was still a part of the martian crust, an asteroid or comet impact may have occurred in the same vicinity. Thus older craters may be found near the source crater. And there is one more clue to the meteorite’s origin. The presence of carbonates in the meteorite suggests that the impact site was located in a watery region.

Barlow’s study used her own crater catalog to identify two possible sites of origin for ALH84001. Both are small, elliptical types located in the heavily cratered southern highlands of Mars. The first crater is located in the Sabaeus Sinus region of Mars just south of the planet’s equator. It is located less than 10 kilometers from the second candidate, an older crater in an area that also shows some possible evidence of ancient river and flooding activity.

Region of mars
Sabaeus sinus region of mars
Sabaeus Sinus region of Mars

Why aren’t martian meteorites red?

The oxidized iron produced by weathering in surface rocks gives Mars its red color, but the less-weathered igneous rocks just below the surface are gray or black. None of the martian meteorites are weathered surface samples, but are all igneous rocks crystallized from molten lava near Mars’ surface. They include five different rock types, which do not all appear to be geologically related to each other.

What do they tell us about Mars?

Martian meteorites tell us about several processes occuring at various times throughout Mars’ history. The story begins with mars’ differentiation into core, mantle and crust very soon after planet formation at 4.5 billion years ago. The oldest martian meteorite crystallized from a magma soon thereafter. The younger martian meteorites show us that igneous volcanism continued until at least 1.3 billion years and probably 170 million years. Impacts occurred on the surface throughout Mars’ history.

Many of the martian meteorites show some evidence of interaction with liquid water. Some have igneous minerals with a little water, but most have alteration products (especially salts and clays) caused by weathering. Studies of the lightest elements that make up the atmosphere tell us that Mars’ atmospheric evolution was very different from Earth. Some of the lightest gases from Mars’ atmosphere were lost to space throughout time.

What don’t Martian meteorites tell us and why do we need sample returns?

We do not know where the meteorites came from on the surface of Mars, therefore we can’t use them for “ground truth” for remote sensing studies. We can only infer that one is from the old cratered terrain of the southern highlands and that the rest are from the young volcanic terrain in the northern plains.

The martian meteorites are all igneous rocks and do not tell us as much about mars’ water and atmosphere as we could learn from studies of old sediments and soils. Igneous rocks are not the best candidates for searching from martian life. Sample return missions directed to both old sedimentary rocks and young volcanic rocks are needed for “ground truth” and to better understand volatiles and possible life on Mars.

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