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Nitrogen Cycling and Biosignatures in a Hyperarid Mars Analog Environment
Jianxun Shen1, Aubrey L Zerkle1, Mark W Claire1
1School of Earth and Environmental Sciences and Centre for Exoplanet Science, University of St Andrews, St Andrews, United Kingdom.
Astrobiology
|October 15, 2021
Summary
The Atacama Desert
Area of Science:
- Astrobiology
- Geochemistry
- Microbiology
Background:
- The hyperarid Atacama Desert, a Mars analog, has significant soil nitrate due to minimal leaching.
- Understanding nitrogen (N) cycling is crucial for extraterrestrial life detection.
Purpose of the Study:
- Investigate nitrogen cycling and organic matter dynamics in Atacama's nitrate-rich soils.
- Analyze isotopic signatures across a rainfall gradient to infer microbial processes.
Main Methods:
- Analyzed nitrate and organic carbon/nitrogen concentrations and isotopic compositions (δ15N, δ18O, Δ17O).
- Inferred microbial pathways using metagenomic and enzyme activity data.
- Examined sites across a natural rainfall gradient (<10 mm to >15 mm annual precipitation).
Main Results:
- Atmospheric isotopic signatures are preserved in driest sites (<10 mm rainfall).
- Biological cycling overprints atmospheric signatures in wetter sites (>15 mm rainfall).
- Unique N cycle pathways identified: nitrifier denitrification, alternative nitrification, and organic N loss.
Conclusions:
- Nitrate assimilation is key in hyperarid Mars-like conditions.
- Nitrogen cycling on Mars may involve nitrate assimilation and water-oxygen exchange.
- Early Mars' wetter conditions could have supported life with traceable isotopic markers.
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