PMID- 34339294
OWN - NLM
STAT- MEDLINE
DCOM- 20211015
LR  - 20211015
IS  - 1557-8070 (Electronic)
IS  - 1557-8070 (Linking)
VI  - 21
IP  - 8
DP  - 2021 Aug
TI  - Nitrogen Fixation at Early Mars.
PG  - 968-980
LID - 10.1089/ast.2020.2273 [doi]
AB  - The Mars Science Laboratory (MSL) recently discovered nitrates in Gale Crater 
      (e.g., Stern et al., 2015; Sutter et al., 2017). One possible mechanism for 
      ancient nitrate deposition on Mars is through HNOx formation and rain out in the 
      atmosphere, for which lightning-induced NO is likely the fundamental source. This 
      study investigates nitrogen (N(2)) fixation in early Mars' atmosphere, with 
      implications for early Mars' habitability. We consider a 1 bar atmosphere of 
      background CO(2), with abundance of N(2), hydrogen, and methane varied from 1% to 
      10% to explore a swath of potential early Mars climates. We derive 
      lightning-induced thermochemical equilibrium fluxes of NO and HCN by coupling the 
      lightning-rate parametrization from the study of Romps et al. (2014) with 
      chemical equilibrium with applications, and we use a Geant4 simulation platform 
      to estimate the effect of solar energetic particle events. These fluxes are used 
      as input into KINETICS, the Caltech/JPL coupled photochemistry and transport 
      code, which models the chemistry of 50 species linked by 495 reactions to derive 
      rain-out fluxes of HNOx and HCN. We compute equilibrium concentrations of cyanide 
      and nitrate in a putative northern ocean at early Mars, assuming hydrothermal 
      vent circulation and photoreduction act as the dominant loss mechanisms. We find 
      average oceanic concentrations of  approximately 0.1-2 nM nitrate and  approximately 0.01-2 mM cyanide. HCN 
      is critical for protein synthesis at concentrations >0.01 M (e.g., Holm and 
      Neubeck, 2009), and our result is astrobiologically significant if secondary 
      local concentration mechanisms occurred. Nitrates may act as high-potential 
      electron acceptors for early metabolisms, although the minimum concentration 
      required is unknown. Our study derives concentrations that will be useful for 
      future laboratory studies to investigate the habitability at early Mars. The 
      aqueous nitrate concentrations correspond to surface nitrate precipitates of 
       approximately 1-8 x 10(-4) wt % that may have formed after the evaporation of surface waters, 
      and these values roughly agree with recent MSL measurements.
FAU - Adams, Danica
AU  - Adams D
AUID- ORCID: 0000-0001-9897-9680
AD  - Department of Geological and Planetary Sciences, California Institute of 
      Technology, Pasadena, California, USA.
FAU - Luo, Yangcheng
AU  - Luo Y
AD  - Department of Geological and Planetary Sciences, California Institute of 
      Technology, Pasadena, California, USA.
FAU - Wong, Michael L
AU  - Wong ML
AD  - Department of Astronomy and Astrobiology Program, University of Washington, 
      Seattle, Washington, USA.
AD  - Virtual Planet Laboratory, University of Washington, Seattle, Washington, USA.
FAU - Dunn, Patrick
AU  - Dunn P
AD  - Space Sciences Laboratory, University of California, Berkeley, Berkeley, 
      California, USA.
FAU - Christensen, Madeline
AU  - Christensen M
AD  - Department of Geological and Planetary Sciences, California Institute of 
      Technology, Pasadena, California, USA.
AD  - Bellarmine Preparatory, Tacoma, Washington, USA.
FAU - Dong, Chuanfei
AU  - Dong C
AUID- ORCID: 0000-0002-8990-094X
AD  - Department of Astrophysical Sciences, Princeton University, Princeton, 
      California, USA.
FAU - Hu, Renyu
AU  - Hu R
AD  - Department of Geological and Planetary Sciences, California Institute of 
      Technology, Pasadena, California, USA.
AD  - Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 
      California, USA.
FAU - Yung, Yuk
AU  - Yung Y
AD  - Department of Geological and Planetary Sciences, California Institute of 
      Technology, Pasadena, California, USA.
AD  - Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 
      California, USA.
LA  - eng
PT  - Journal Article
PT  - Research Support, U.S. Gov't, Non-P.H.S.
DEP - 20210730
PL  - United States
TA  - Astrobiology
JT  - Astrobiology
JID - 101088083
RN  - 0 (Nitrates)
SB  - IM
MH  - Atmosphere
MH  - Extraterrestrial Environment
MH  - *Mars
MH  - Nitrates
MH  - *Nitrogen Fixation
OTO - NOTNLM
OT  - Astrobiology
OT  - Early Mars
OT  - Nitrate.
OT  - Nitrogen fixation
EDAT- 2021/08/03 06:00
MHDA- 2021/10/16 06:00
CRDT- 2021/08/02 17:12
PHST- 2021/08/03 06:00 [pubmed]
PHST- 2021/10/16 06:00 [medline]
PHST- 2021/08/02 17:12 [entrez]
AID - 10.1089/ast.2020.2273 [doi]
PST - ppublish
SO  - Astrobiology. 2021 Aug;21(8):968-980. doi: 10.1089/ast.2020.2273. Epub 2021 Jul 
      30.