The nitrogen cycle on Mars: Impact decomposition of near-surface nitrates as a source for a nitrogen steady state |
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Authors: | Curtis V Manning Christopher P McKay Kevin J Zahnle |
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Institution: | NASA-Ames Research Center, MS 245-3, Moffett Field, CA 94035-1000, USA |
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Abstract: | Nitrogen isotopes appear to be escaping from Mars at approximately the primordial ratio 14N/15N ≈ 275 and to have an atmospheric nitrogen depletion time scale of about 800 Myr. For the standard model of a progressive decline of an initial inventory of atmospheric nitrogen, having no source of N, the agreement of the isotopic ratio of escaping N with primitive nitrogen would be coincidental. Here we propose a steady state model in which nitrates, produced early in Mars' history, are later decomposed by the current impact flux. The detection of near-surface nitrates can discriminate between the standard and the steady state models. Based on current estimates of N loss to space, we predict a quantity of nitrates equivalent to 60 ± 30 mbars for a steady state, or a global layer of about 3 m of pure NaNO3. |
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Keywords: | Mars atmosphere Mars surface Atmospheres evolution Impact processes |
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