Mathematics – Logic
Scientific paper
Sep 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009dps....41.5403s&link_type=abstract
American Astronomical Society, DPS meeting #41, #54.03
Mathematics
Logic
Scientific paper
The abiotic fixation of nitrogen is critical to planetary evolution and the potential for life on terrestrial planets. A non-biological source of nitrogen, in a biochemically accessible form, is necessary for the origin and early evolution of life. Loss of nitrogen can result in atmospheric pressures too low for liquid water and will impact planetary habitability and hydrological processes.
Shock heating of a non-reducing atmosphere produces NO and this has been well studied. Our understanding of the subsequent reactions was, in the past, theoretical. It was postulated that NO was photochemically converted to HNO which then, in surface waters, reacts to form nitrate and nitrite.
This chemistry, including reactions in both the gas phase and the liquid phase, has now been studied experimentally. Our work has observed that there are multiple pathways for the fixation. One pathway observed is consistent with the theoretically predicted route via the formation of HNO. Interestingly, this pathway is coupled to photochemical formation of formaldehyde from CO through the formation of HCO. In the presence of liquid water, this pathway leads to the formation of nitrate and nitrite. In the presence of water vapor, but no liquid water, HNO appears to mostly dimerize to form N2O.
A second pathway involves the formation of NO2 from CO2 and NO. This pathway becomes more dominant without water, but the reaction of NO2 with even adsorbed water can lead to the formation of nitric acid.
Finally, with FeS suspended in liquid water, the direct reduction of NO to ammonia is observed. This last pathway represents the most efficient way to reduced nitrogen, with product yields well above 20% (nitrite/nitrate, from the first two pathways can also be reduced to ammonia thought the overall efficiency suffers).
We wish to thank the NASA Astrobiology Institute for support.
Basa Ranor C. B.
Khare Bishun
Rodoni David
Summers David P.
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