Methane on Mars and Habitability: Challenges and Responses

Yuk L. Yung, Pin Chen, Kenneth Nealson, Sushil Atreya, Patrick Beckett, Jennifer G. Blank, Bethany Ehlmann, John Eiler, Giuseppe Etiope, James G. Ferry, Francois Forget, Peter Gao, Renyu Hu, Armin Kleinböhl, Ronald Klusman, Franck Lefèvre, Charles Miller, Michael Mischna, Michael Mumma, Sally NewmanDorothy Oehler, Mitchio Okumura, Ronald Oremland, Victoria Orphan, Radu Popa, Michael Russell, Linhan Shen, Barbara Sherwood Lollar, Robert Staehle, Vlada Stamenković, Daniel Stolper, Alexis Templeton, Ann C. Vandaele, Sébastien Viscardy, Christopher R. Webster, Paul O. Wennberg, Michael L. Wong, John Worden

Research output: Contribution to journalReview article

13 Citations (Scopus)

Abstract

Recent measurements of methane (CH4) by the Mars Science Laboratory (MSL) now confront us with robust data that demand interpretation. Thus far, the MSL data have revealed a baseline level of CH4 (∼0.4 parts per billion by volume [ppbv]), with seasonal variations, as well as greatly enhanced spikes of CH4 with peak abundances of ∼7 ppbv. What do these CH4 revelations with drastically different abundances and temporal signatures represent in terms of interior geochemical processes, or is martian CH4 a biosignature? Discerning how CH4 generation occurs on Mars may shed light on the potential habitability of Mars. There is no evidence of life on the surface of Mars today, but microbes might reside beneath the surface. In this case, the carbon flux represented by CH4 would serve as a link between a putative subterranean biosphere on Mars and what we can measure above the surface. Alternatively, CH4 records modern geochemical activity. Here we ask the fundamental question: how active is Mars, geochemically and/or biologically? In this article, we examine geological, geochemical, and biogeochemical processes related to our overarching question. The martian atmosphere and surface are an overwhelmingly oxidizing environment, and life requires pairing of electron donors and electron acceptors, that is, redox gradients, as an essential source of energy. Therefore, a fundamental and critical question regarding the possibility of life on Mars is, "Where can we find redox gradients as energy sources for life on Mars?" Hence, regardless of the pathway that generates CH4 on Mars, the presence of CH4, a reduced species in an oxidant-rich environment, suggests the possibility of redox gradients supporting life and habitability on Mars. Recent missions such as ExoMars Trace Gas Orbiter may provide mapping of the global distribution of CH4. To discriminate between abiotic and biotic sources of CH4 on Mars, future studies should use a series of diagnostic geochemical analyses, preferably performed below the ground or at the ground/atmosphere interface, including measurements of CH4 isotopes, methane/ethane ratios, H2 gas concentration, and species such as acetic acid. Advances in the fields of Mars exploration and instrumentation will be driven, augmented, and supported by an improved understanding of atmospheric chemistry and dynamics, deep subsurface biogeochemistry, astrobiology, planetary geology, and geophysics. Future Mars exploration programs will have to expand the integration of complementary areas of expertise to generate synergistic and innovative ideas to realize breakthroughs in advancing our understanding of the potential of life and habitable conditions having existed on Mars. In this spirit, we conducted a set of interdisciplinary workshops. From this series has emerged a vision of technological, theoretical, and methodological innovations to explore the martian subsurface and to enhance spatial tracking of key volatiles, such as CH4.

Original languageEnglish (US)
Pages (from-to)1221-1242
Number of pages22
JournalAstrobiology
Volume18
Issue number10
DOIs
StatePublished - Oct 2018

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habitability
Mars
Methane
mars
methane
Mars exploration
Oxidation-Reduction
planetary geology
gradients
biogeochemistry
Atmosphere
exobiology
atmospheres
biosphere
atmospheric chemistry
Exobiology
geophysics
Gases
Geology
microorganisms

All Science Journal Classification (ASJC) codes

  • Agricultural and Biological Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Yung, Y. L., Chen, P., Nealson, K., Atreya, S., Beckett, P., Blank, J. G., ... Worden, J. (2018). Methane on Mars and Habitability: Challenges and Responses. Astrobiology, 18(10), 1221-1242. https://doi.org/10.1089/ast.2018.1917
Yung, Yuk L. ; Chen, Pin ; Nealson, Kenneth ; Atreya, Sushil ; Beckett, Patrick ; Blank, Jennifer G. ; Ehlmann, Bethany ; Eiler, John ; Etiope, Giuseppe ; Ferry, James G. ; Forget, Francois ; Gao, Peter ; Hu, Renyu ; Kleinböhl, Armin ; Klusman, Ronald ; Lefèvre, Franck ; Miller, Charles ; Mischna, Michael ; Mumma, Michael ; Newman, Sally ; Oehler, Dorothy ; Okumura, Mitchio ; Oremland, Ronald ; Orphan, Victoria ; Popa, Radu ; Russell, Michael ; Shen, Linhan ; Sherwood Lollar, Barbara ; Staehle, Robert ; Stamenković, Vlada ; Stolper, Daniel ; Templeton, Alexis ; Vandaele, Ann C. ; Viscardy, Sébastien ; Webster, Christopher R. ; Wennberg, Paul O. ; Wong, Michael L. ; Worden, John. / Methane on Mars and Habitability : Challenges and Responses. In: Astrobiology. 2018 ; Vol. 18, No. 10. pp. 1221-1242.
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Yung, YL, Chen, P, Nealson, K, Atreya, S, Beckett, P, Blank, JG, Ehlmann, B, Eiler, J, Etiope, G, Ferry, JG, Forget, F, Gao, P, Hu, R, Kleinböhl, A, Klusman, R, Lefèvre, F, Miller, C, Mischna, M, Mumma, M, Newman, S, Oehler, D, Okumura, M, Oremland, R, Orphan, V, Popa, R, Russell, M, Shen, L, Sherwood Lollar, B, Staehle, R, Stamenković, V, Stolper, D, Templeton, A, Vandaele, AC, Viscardy, S, Webster, CR, Wennberg, PO, Wong, ML & Worden, J 2018, 'Methane on Mars and Habitability: Challenges and Responses', Astrobiology, vol. 18, no. 10, pp. 1221-1242. https://doi.org/10.1089/ast.2018.1917

Methane on Mars and Habitability : Challenges and Responses. / Yung, Yuk L.; Chen, Pin; Nealson, Kenneth; Atreya, Sushil; Beckett, Patrick; Blank, Jennifer G.; Ehlmann, Bethany; Eiler, John; Etiope, Giuseppe; Ferry, James G.; Forget, Francois; Gao, Peter; Hu, Renyu; Kleinböhl, Armin; Klusman, Ronald; Lefèvre, Franck; Miller, Charles; Mischna, Michael; Mumma, Michael; Newman, Sally; Oehler, Dorothy; Okumura, Mitchio; Oremland, Ronald; Orphan, Victoria; Popa, Radu; Russell, Michael; Shen, Linhan; Sherwood Lollar, Barbara; Staehle, Robert; Stamenković, Vlada; Stolper, Daniel; Templeton, Alexis; Vandaele, Ann C.; Viscardy, Sébastien; Webster, Christopher R.; Wennberg, Paul O.; Wong, Michael L.; Worden, John.

In: Astrobiology, Vol. 18, No. 10, 10.2018, p. 1221-1242.

Research output: Contribution to journalReview article

TY - JOUR

T1 - Methane on Mars and Habitability

T2 - Challenges and Responses

AU - Yung, Yuk L.

AU - Chen, Pin

AU - Nealson, Kenneth

AU - Atreya, Sushil

AU - Beckett, Patrick

AU - Blank, Jennifer G.

AU - Ehlmann, Bethany

AU - Eiler, John

AU - Etiope, Giuseppe

AU - Ferry, James G.

AU - Forget, Francois

AU - Gao, Peter

AU - Hu, Renyu

AU - Kleinböhl, Armin

AU - Klusman, Ronald

AU - Lefèvre, Franck

AU - Miller, Charles

AU - Mischna, Michael

AU - Mumma, Michael

AU - Newman, Sally

AU - Oehler, Dorothy

AU - Okumura, Mitchio

AU - Oremland, Ronald

AU - Orphan, Victoria

AU - Popa, Radu

AU - Russell, Michael

AU - Shen, Linhan

AU - Sherwood Lollar, Barbara

AU - Staehle, Robert

AU - Stamenković, Vlada

AU - Stolper, Daniel

AU - Templeton, Alexis

AU - Vandaele, Ann C.

AU - Viscardy, Sébastien

AU - Webster, Christopher R.

AU - Wennberg, Paul O.

AU - Wong, Michael L.

AU - Worden, John

PY - 2018/10

Y1 - 2018/10

N2 - Recent measurements of methane (CH4) by the Mars Science Laboratory (MSL) now confront us with robust data that demand interpretation. Thus far, the MSL data have revealed a baseline level of CH4 (∼0.4 parts per billion by volume [ppbv]), with seasonal variations, as well as greatly enhanced spikes of CH4 with peak abundances of ∼7 ppbv. What do these CH4 revelations with drastically different abundances and temporal signatures represent in terms of interior geochemical processes, or is martian CH4 a biosignature? Discerning how CH4 generation occurs on Mars may shed light on the potential habitability of Mars. There is no evidence of life on the surface of Mars today, but microbes might reside beneath the surface. In this case, the carbon flux represented by CH4 would serve as a link between a putative subterranean biosphere on Mars and what we can measure above the surface. Alternatively, CH4 records modern geochemical activity. Here we ask the fundamental question: how active is Mars, geochemically and/or biologically? In this article, we examine geological, geochemical, and biogeochemical processes related to our overarching question. The martian atmosphere and surface are an overwhelmingly oxidizing environment, and life requires pairing of electron donors and electron acceptors, that is, redox gradients, as an essential source of energy. Therefore, a fundamental and critical question regarding the possibility of life on Mars is, "Where can we find redox gradients as energy sources for life on Mars?" Hence, regardless of the pathway that generates CH4 on Mars, the presence of CH4, a reduced species in an oxidant-rich environment, suggests the possibility of redox gradients supporting life and habitability on Mars. Recent missions such as ExoMars Trace Gas Orbiter may provide mapping of the global distribution of CH4. To discriminate between abiotic and biotic sources of CH4 on Mars, future studies should use a series of diagnostic geochemical analyses, preferably performed below the ground or at the ground/atmosphere interface, including measurements of CH4 isotopes, methane/ethane ratios, H2 gas concentration, and species such as acetic acid. Advances in the fields of Mars exploration and instrumentation will be driven, augmented, and supported by an improved understanding of atmospheric chemistry and dynamics, deep subsurface biogeochemistry, astrobiology, planetary geology, and geophysics. Future Mars exploration programs will have to expand the integration of complementary areas of expertise to generate synergistic and innovative ideas to realize breakthroughs in advancing our understanding of the potential of life and habitable conditions having existed on Mars. In this spirit, we conducted a set of interdisciplinary workshops. From this series has emerged a vision of technological, theoretical, and methodological innovations to explore the martian subsurface and to enhance spatial tracking of key volatiles, such as CH4.

AB - Recent measurements of methane (CH4) by the Mars Science Laboratory (MSL) now confront us with robust data that demand interpretation. Thus far, the MSL data have revealed a baseline level of CH4 (∼0.4 parts per billion by volume [ppbv]), with seasonal variations, as well as greatly enhanced spikes of CH4 with peak abundances of ∼7 ppbv. What do these CH4 revelations with drastically different abundances and temporal signatures represent in terms of interior geochemical processes, or is martian CH4 a biosignature? Discerning how CH4 generation occurs on Mars may shed light on the potential habitability of Mars. There is no evidence of life on the surface of Mars today, but microbes might reside beneath the surface. In this case, the carbon flux represented by CH4 would serve as a link between a putative subterranean biosphere on Mars and what we can measure above the surface. Alternatively, CH4 records modern geochemical activity. Here we ask the fundamental question: how active is Mars, geochemically and/or biologically? In this article, we examine geological, geochemical, and biogeochemical processes related to our overarching question. The martian atmosphere and surface are an overwhelmingly oxidizing environment, and life requires pairing of electron donors and electron acceptors, that is, redox gradients, as an essential source of energy. Therefore, a fundamental and critical question regarding the possibility of life on Mars is, "Where can we find redox gradients as energy sources for life on Mars?" Hence, regardless of the pathway that generates CH4 on Mars, the presence of CH4, a reduced species in an oxidant-rich environment, suggests the possibility of redox gradients supporting life and habitability on Mars. Recent missions such as ExoMars Trace Gas Orbiter may provide mapping of the global distribution of CH4. To discriminate between abiotic and biotic sources of CH4 on Mars, future studies should use a series of diagnostic geochemical analyses, preferably performed below the ground or at the ground/atmosphere interface, including measurements of CH4 isotopes, methane/ethane ratios, H2 gas concentration, and species such as acetic acid. Advances in the fields of Mars exploration and instrumentation will be driven, augmented, and supported by an improved understanding of atmospheric chemistry and dynamics, deep subsurface biogeochemistry, astrobiology, planetary geology, and geophysics. Future Mars exploration programs will have to expand the integration of complementary areas of expertise to generate synergistic and innovative ideas to realize breakthroughs in advancing our understanding of the potential of life and habitable conditions having existed on Mars. In this spirit, we conducted a set of interdisciplinary workshops. From this series has emerged a vision of technological, theoretical, and methodological innovations to explore the martian subsurface and to enhance spatial tracking of key volatiles, such as CH4.

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Yung YL, Chen P, Nealson K, Atreya S, Beckett P, Blank JG et al. Methane on Mars and Habitability: Challenges and Responses. Astrobiology. 2018 Oct;18(10):1221-1242. https://doi.org/10.1089/ast.2018.1917