Evaluation of meteorites as habitats for terrestrial microorganisms

Results from the Nullarbor Plain, Australia, a Mars analogue site

Alastair W. Tait, Siobhan A. Wilson, Andrew G. Tomkins, Emma J. Gagen, Stewart J Fallon, Gordon Southam

Research output: Contribution to journalArticleResearchpeer-review

3 Citations (Scopus)

Abstract

Unambiguous identification of biosignatures on Mars requires access to well-characterized, long-lasting geochemical standards at the planet's surface that can be modified by theoretical martian life. Ordinary chondrites, which are ancient meteorites that commonly fall to the surface of Mars and Earth, have well-characterized, narrow ranges in trace element and isotope geochemistry compared to martian rocks. Given that their mineralogy is more attractive to known chemolithotrophic life than the basaltic rocks that dominate the martian surface, exogenic rocks (e.g., chondritic meteorites) may be good places to look for signs of prior life endemic to Mars. In this study, we show that ordinary chondrites, collected from the arid Australian Nullarbor Plain, are commonly colonized and inhabited by terrestrial microorganisms that are endemic to this Mars analogue site. These terrestrial endolithic and chasmolithic microbial contaminants are commonly found in close association with hygroscopic veins of gypsum and Mg-calcite, which have formed within cracks penetrating deep into the meteorites. Terrestrial bacteria are observed within corrosion cavities, where troilite (FeS) oxidation has produced jarosite [KFe3(SO4)2(OH)6]. Where terrestrial microorganisms have colonized primary silicate minerals and secondary calcite, these mineral surfaces are heavily etched. Our results show that inhabitation of meteorites by terrestrial microorganisms in arid environments relies upon humidity and pH regulation by minerals. Furthermore, microbial colonization affects the weathering of meteorites and production of sulfate, carbonate, Fe-oxide and smectite minerals that can preserve chemical and isotopic biosignatures for thousands to millions of years on Earth. Meteorites are thus habitable by terrestrial microorganisms, even under highly desiccating environmental conditions of relevance to Mars. They may therefore be useful as chemical and isotopic “standards” that preserve evidence of life, thereby providing the possibility of universal context for recognition of microbial biosignatures on Earth, Mars and throughout the solar system.

Original languageEnglish
Pages (from-to)1-16
Number of pages16
JournalGeochimica et Cosmochimica Acta
Volume215
DOIs
Publication statusPublished - 15 Oct 2017

Keywords

  • Astrobiology
  • Biomarker
  • Chondrites
  • Deliquescence
  • Isotopic standard
  • Mars
  • Mars analogues
  • Meteorites
  • Nullarbor Plain

Cite this

Tait, Alastair W. ; Wilson, Siobhan A. ; Tomkins, Andrew G. ; Gagen, Emma J. ; Fallon, Stewart J ; Southam, Gordon. / Evaluation of meteorites as habitats for terrestrial microorganisms : Results from the Nullarbor Plain, Australia, a Mars analogue site. In: Geochimica et Cosmochimica Acta. 2017 ; Vol. 215. pp. 1-16.
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abstract = "Unambiguous identification of biosignatures on Mars requires access to well-characterized, long-lasting geochemical standards at the planet's surface that can be modified by theoretical martian life. Ordinary chondrites, which are ancient meteorites that commonly fall to the surface of Mars and Earth, have well-characterized, narrow ranges in trace element and isotope geochemistry compared to martian rocks. Given that their mineralogy is more attractive to known chemolithotrophic life than the basaltic rocks that dominate the martian surface, exogenic rocks (e.g., chondritic meteorites) may be good places to look for signs of prior life endemic to Mars. In this study, we show that ordinary chondrites, collected from the arid Australian Nullarbor Plain, are commonly colonized and inhabited by terrestrial microorganisms that are endemic to this Mars analogue site. These terrestrial endolithic and chasmolithic microbial contaminants are commonly found in close association with hygroscopic veins of gypsum and Mg-calcite, which have formed within cracks penetrating deep into the meteorites. Terrestrial bacteria are observed within corrosion cavities, where troilite (FeS) oxidation has produced jarosite [KFe3(SO4)2(OH)6]. Where terrestrial microorganisms have colonized primary silicate minerals and secondary calcite, these mineral surfaces are heavily etched. Our results show that inhabitation of meteorites by terrestrial microorganisms in arid environments relies upon humidity and pH regulation by minerals. Furthermore, microbial colonization affects the weathering of meteorites and production of sulfate, carbonate, Fe-oxide and smectite minerals that can preserve chemical and isotopic biosignatures for thousands to millions of years on Earth. Meteorites are thus habitable by terrestrial microorganisms, even under highly desiccating environmental conditions of relevance to Mars. They may therefore be useful as chemical and isotopic “standards” that preserve evidence of life, thereby providing the possibility of universal context for recognition of microbial biosignatures on Earth, Mars and throughout the solar system.",
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Evaluation of meteorites as habitats for terrestrial microorganisms : Results from the Nullarbor Plain, Australia, a Mars analogue site. / Tait, Alastair W.; Wilson, Siobhan A.; Tomkins, Andrew G.; Gagen, Emma J.; Fallon, Stewart J; Southam, Gordon.

In: Geochimica et Cosmochimica Acta, Vol. 215, 15.10.2017, p. 1-16.

Research output: Contribution to journalArticleResearchpeer-review

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AU - Tait, Alastair W.

AU - Wilson, Siobhan A.

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AB - Unambiguous identification of biosignatures on Mars requires access to well-characterized, long-lasting geochemical standards at the planet's surface that can be modified by theoretical martian life. Ordinary chondrites, which are ancient meteorites that commonly fall to the surface of Mars and Earth, have well-characterized, narrow ranges in trace element and isotope geochemistry compared to martian rocks. Given that their mineralogy is more attractive to known chemolithotrophic life than the basaltic rocks that dominate the martian surface, exogenic rocks (e.g., chondritic meteorites) may be good places to look for signs of prior life endemic to Mars. In this study, we show that ordinary chondrites, collected from the arid Australian Nullarbor Plain, are commonly colonized and inhabited by terrestrial microorganisms that are endemic to this Mars analogue site. These terrestrial endolithic and chasmolithic microbial contaminants are commonly found in close association with hygroscopic veins of gypsum and Mg-calcite, which have formed within cracks penetrating deep into the meteorites. Terrestrial bacteria are observed within corrosion cavities, where troilite (FeS) oxidation has produced jarosite [KFe3(SO4)2(OH)6]. Where terrestrial microorganisms have colonized primary silicate minerals and secondary calcite, these mineral surfaces are heavily etched. Our results show that inhabitation of meteorites by terrestrial microorganisms in arid environments relies upon humidity and pH regulation by minerals. Furthermore, microbial colonization affects the weathering of meteorites and production of sulfate, carbonate, Fe-oxide and smectite minerals that can preserve chemical and isotopic biosignatures for thousands to millions of years on Earth. Meteorites are thus habitable by terrestrial microorganisms, even under highly desiccating environmental conditions of relevance to Mars. They may therefore be useful as chemical and isotopic “standards” that preserve evidence of life, thereby providing the possibility of universal context for recognition of microbial biosignatures on Earth, Mars and throughout the solar system.

KW - Astrobiology

KW - Biomarker

KW - Chondrites

KW - Deliquescence

KW - Isotopic standard

KW - Mars

KW - Mars analogues

KW - Meteorites

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