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2009 Annual Science Report

VPL at University of Washington Reporting  |  JUL 2008 – AUG 2009

Postdoctoral Fellow Report: Mark Claire

Project Summary

I am interested in how biological gases affect the atmosphere of Earth (and possibly other planets.) Specifically, I use computer models to investigate how biogenic sulfur gases might build up in a planetary atmosphere, and if this would lead to observable traces in Earth’s rock record or in the atmospheres of planets around other stars. I’m also working on how anaerobic oxidizers of methane affected the rise of oxygen on Earth, and if evolutionary changes in nitrogen-using bacteria may have changed global N2 levels and planetary climate.

4 Institutions
3 Teams
2 Publications
0 Field Sites
Field Sites

Project Progress

This document reports on activities during the first five months of my NAI/NPP postdoctoral fellowship. Significant model development was undertaken, and a first publication on the astronomical detection of biogenic sulfur gases – the first such biosignatures described for an anoxic planet – is nearly ready for submission.

For the biogenic sulfur project (described in Project Report “Detectability of Biosignatures”), I enhanced the VPL photochemical model to enable simple user changes for chemical species, reaction rates, and boundary conditions. I also helped compile the chemical reaction tables for biogenic sulfur gases.

During the period of performance, I also added chlorine species to the model as described in Project Report “Understanding the Early Mars Environment”. The publication relating to this work (Catling et al. 2009) focused on modern Earth and Mars environments, but has enabled the first investigation of chlorine species on the Archean earth, which is underway.

In addition, I worked to complete a number of additional VPL related projects during this time period. These include:

  • I enhanced my numerical model for the early Solar flux, which I hope to publish during the next performance period. Working with VPL co-investigator Martin Cohen, I extended the results of Ribas et al. 2005 into the near UV. A portion of this work was published with colleagues from the Ames team (Goldblatt et al. 2009), and plays a significant role in estimating the climatic effects of the Faint Young Sun.
  • I collaborated with Emily Beal and Chris House of the PSU team on a combined laboratory/modeling study of how anaerobic oxidizers of methane may have modulated atmospheric chemistry during and after the great oxidation event. (Beal et al. 2009, in review)

References:
Beal, E., Claire, M, and House, C.. “The effect of sulfate concentration on the rate of the anaerobic oxidation of methane” in review, 2009.
Catling, D., Claire, M., Zahnle, K., Quinn, R., Clark, B., Hecht, M., Kounaves, S. “Atmospheric origins of perchlorate on Mars and in the Atacama”, in press JGR, 2009
Goldblatt C., Claire, M., Lenton, T., Matthews, A., Watson, A., Zahnle, K. “Nitrogen-enhanced greenhouse warming on the early Earth” in press, Nature Geosciences, 2009

Publications

  • Catling, D. C., Claire, M. W., Zahnle, K. J., Quinn, R. C., Clark, B. C., Hecht, M. H., & Kounaves, S. (2010). Atmospheric origins of perchlorate on Mars and in the Atacama. Journal of Geophysical Research, 115. doi:10.1029/2009je003425

  • Claire, M., Catling, D. & Zahnle, K.  (2008).  First Results froms a Time-dependent 1D early Earth Photochemical Model.  Astrobiology, 8(2): 423.