Nitrogen Oxide Concentrations in Natural Waters on Early Earth
Name
2018GC008082.pdf
Description
Published version
Size
1.68 MB
Format
Adobe PDF
Checksum (MD5)
fd244c82c48dd892647a607ae109bd38
Author(s)
Ranjan, Sukrit
Todd, Zoe R.
Rimmer, Paul R.
Sasselov, Dimitar D.
Babbin, Andrew R.
Date Issued
April 2019
Journal
Geochemistry, Geophysics, Geosystems
Publisher
American Geophysical Union (AGU)
Citation
Ranjan, Sukrit, et al. “Nitrogen Oxide Concentrations in Natural Waters on Early Earth.” Geochemistry, Geophysics, Geosystems 20, 4 (April 2019): 2021–39. © 2019 The Authors
Version
Final published version
Abstract
A key challenge in origins-of-life studies is estimating the abundances of species relevant to the chemical pathways proposed to have contributed to the emergence of life on early Earth. Dissolved nitrogen oxide anions (NO-[subscript x]), in particular nitrate (NO-[subscript 3]) and nitrite (NO-[subscript 2]), have been invoked in diverse origins-of-life chemistry, from the oligomerization of RNA to the emergence of protometabolism. Recent work has calculated the supply of NO-[subscript x] from the prebiotic atmosphere to the ocean and reported steady state [NO-[subscript x] to be high across all plausible parameter space. These findings rest on the assumption that NO-[subscript x] is stable in natural waters unless processed at a hydrothermal vent. Here, we show that NO-[subscript x] is unstable in the reducing environment of early Earth. Sinks due to ultraviolet photolysis and reactions with reduced iron (Fe[superscript 2+]) suppress [NO-[subscript x]] by several orders of magnitude relative to past predictions. For pH = 6.5–8 and T = 0–50 °C, we find that it is most probable that [NO-[subscript x]] <1μM in the prebiotic ocean. On the other hand, prebiotic ponds with favorable drainage characteristics may have sustained [NO-[subscript x]] ≥1μM. As on modern Earth, most NO-[subscript x] on prebiotic Earth should have been present as NO-[subscript 3], due to its much greater stability. These findings inform the kind of prebiotic chemistries that would have been possible on early Earth. We discuss the implications for proposed prebiotic chemistries and highlight the need for further studies of NO-[subscript x] kinetics to reduce the considerable uncertainties in predicting [NO-[subscript x]] on early Earth.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Terms of Use
Creative Commons Attribution-NonCommercial-NoDerivs License
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DOI of Published Version
https://doi.org/10.1029/2018GC008082
