Sarah Stewart Johnson

Sarah Stewart Johnson
Assistant Professor
512 ICC

Assistant Professor

Sarah Stewart Johnson’s scientific research focuses on the evolution of planetary environments, particularly with regard to the search for life on Mars. She has created models of the early Martian atmosphere, completed field seasons in Antarctica, Australia and Madagascar, conducted research at the Niels Bohr Institute in Copenhagen, and worked on the NASA Science Team for the Opportunity and Spirit Mars Rovers.

Sarah also worked as a White House Fellow for the President’s Science Advisor during the first term of the Obama Administration. Just prior to joining the Georgetown faculty in 2014, she was a Junior Fellow in the Harvard Society of Fellows.

She is a Goldwater, Truman, and Rhodes Scholar, and a National Science Foundation Graduate Fellow. She holds a B.A. in mathematics and environmental studies from Washington University in St. Louis, a second B.A. in philosophy, politics and economics and M.Sc. in biology from Oxford University, and a Ph.D. in planetary science from the Massachusetts Institute of Technology.

  • Ph.D. Massachusetts Institute of Technology
  • M.Sc Oxford University
  • B.A. Oxford University
  • B.A. Washington University in St. Louis

Areas of Expertise: space exploration, Mars, climate, geobiology


Johnson, S. S., et al., 2015. Insights from the metagenome of an acid salt lake: the role of biology in an extreme depositional environment.  PLOS ONE.

Johnson, S. S., O-Rings, 2014.  Best American Science and Nature Writing. Boston: Houghton Mifflin Harcourt, p. 107-114.

Johnson, S. S., et al., 2009.  Fate of SO2 in the ancient Martian atmosphere: implications for transient greenhouse warming. Journal of Geophysical Research, 114, E11011.

Johnson, S. S., et al., 2008.  Sulfur-induced Greenhouse Warming on Early Mars. Journal of Geophysical Research, 113, E08005.

Isenbarger, T. A., et al., 2008.  The most conserved genome segments for life detection on Earth and other planets. Origins of Life and Evolution of Biospheres, 38(6), 517–533.

Johnson, S. S., et al., 2007.  Ancient Bacteria Show Evidence of DNA Repair. Proceedings of the National Academy of Sciences, 104(36), 14401-14405.

Herkenhoff, K. E., et al., 2006, Overview of the Microscopic Imager Investigation during Spirit’s first 450 sols in Gusev crater. Journal of Geophysical Research. 111, E02S04.

McLennan, S. M., et al., 2005. Provenance and diagenesis of the evaporate-bearing Burns formation, Meridiani Planum, Mars. Earth and Planetary Science Letters, 240, 95 – 121.

Ehlmann, B. L., et al., 2005.  Hydrologic and Isotopic Modeling of Alpine Lake Waiau. Pacific Science, 59(1), 1-15.

Arvidson, R. E., et al., 1999, Aerobot Measurements Successfully Obtained During Solo Spirit Balloon Mission. Eos Trans. AGU, 80(14), 153, doi:10.1029/99EO00106.