Nitrogen isotope ratios trace high-pH conditions in a terrestrial Mars analog site.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32133401.
- Also identified by DOI 10.1126/sciadv.aay3440 and PMC identifier 7043907.
- Licence recorded as CC BY-NC.
- Because redistribution is not established, this page shows the abstract only. Follow the links below for the full text.
Abstract
High-pH alkaline lakes are among the most productive ecosystems on Earth and prime targets in the search for life on Mars; however, a robust proxy for such settings does not yet exist. Nitrogen isotope fractionation resulting from NH<sub>3</sub> volatilization at high pH has the potential to fill this gap. To validate this idea, we analyzed samples from the Nördlinger Ries, a Miocene impact crater lake that displayed pH values up to 9.8 as inferred from mineralogy and aqueous modeling. Our data show a peak in δ<sup>15</sup>N of +17‰ in the most alkaline facies, followed by a gradual decline to around +5‰, concurrent with the proposed decline in pH, highlighting the utility of nitrogen isotopes as a proxy for high-pH conditions. In combination with independent mineralogical indicators for high alkalinity, nitrogen isotopes can provide much-needed quantitative constraints on ancient atmospheric <i>P</i>co<sub>2</sub> (partial pressure of CO<sub>2</sub>) and thus climatic controls on early Earth and Mars.