Publications

Life on Venus

Our hypothesized life cycle for the hypothetical microbial life in the Venusian atmosphere. The paper includes a detailed description of  the extreme challenges to life of any kind in the Venusian atmosphere.

Seager, S., Petkowski, J. J., Gao, P., Bains, W., Bryan, N. C., Ranjan, S., & Greaves, J. (2020).
The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere. Astrobiology.

People wonder about silicon-based life. Pure silicon-based life is impossible primarily because of the instability of  silicon molecules in water and ubiquitous silica formation. Surprisingly, we found that sulfuric acid as a liquid environment supports a much larger diversity of organosilicon chemistry than liquid water does.

Petkowski, J. J., Bains, W., & Seager, S. (2020).
On the Potential of Silicon as a Building Block for Life. Life, 10(6), 84.

Phosphine

Discovery paper of PH3 in the Venusian atmosphere and its implications for the presence of life.
Greaves, Jane S., Richards, Anita M. S., Bains, William, Rimmer, Paul B., Sagawa, Hideo, Clements, David L., Seager, Sara, Petkowski, Janusz J., Sousa-Silva, Clara, Ranjan, Sukrit, Drabek-Maunder, Emily, Fraser, Helen J., Cartwright, Annabel, Mueller-Wodarg, Ingo, Zhan, Zhuchang, Friberg, Per, Coulson, Iain, Hoge, Jim. (2020).
Phosphine Gas in the Cloud Decks of Venus. Nature Astronomy, in press.

A supplementary paper to the PH3 on Venus discovery paper. Here we expand on the arguments that no known atmospheric, surface, or subsurface chemistry can explain the presence of PH3.
Bains, William, Petkowski, Janusz J, Seager, Sara, Ranjan, Sukrit, Sousa-Silva, Clara, Rimmer Paul, Zhan, Zhuchang, Greaves, Jane, Richards, Anita. (2020).
Phosphine on Venus Cannot be Explained by Conventional Processes. Astrobiology under revision.

We present a new model for the biological production of phosphine in specific anaerobic environments, where the combined action of phosphate reducing and phosphite disproportionating bacteria can produce phosphine (PH3).
Bains, W., Petkowski, J. J., Sousa-Silva, C., & Seager, S. (2019).
New Environmental Model for Thermodynamic Ecology of Biological Phosphine Production. Science of The Total Environment, 658, 521-536.

Many scientists are not aware or do not believe phosphine is produced by life. In this paper we list and then dispel the four main arguments against (too toxic, no direct evidence of production from a specific species, too energetically costly to produce, unstable in O2-rich environment ) We postulate that anaerobic life persisting in anoxic (O2-free) environments may exploit trivalent phosphorus chemistry much more extensively, in contrast to O2-dependent life for which phosphine is highly toxic.
Bains, W., Petkowski, J. J., Sousa-Silva, C., & Seager, S. (2019).
Trivalent Phosphorus and Phosphines as Components of Biochemistry in Anoxic Environments. Astrobiology, 19(7), 885-902.

We make the case for PH3 as a biosignature gas on exoplanets. The main conclusion is massive amounts of PH3 need to be produced by life on an exoplanet in order to generate enough PH3 to accumulate in the atmosphere for hypothetical remote sensing detection.
Sousa-Silva, C., Seager, S., Ranjan, S., Petkowski, J. J., Zhan, Z., Hu, R., & Bains, W. (2020).
Phosphine as a Biosignature Gas in Exoplanet Atmospheres. Astrobiology, 20(2), 235-268.

Phosphine Discovery in the Venusian Atmosphere

On September 14, 2020 Dr. Jane Greaves of Cardiff University announced that she detected phosphine in Venus’ atmosphere using the James Clerk Maxwell Telescope (JCMT) in Hawaii, and the Atacama Large Millimeter Array (ALMA) observatory in Chile.

The MIT team, led by Prof. Sara Seager, Dr. Janusz Petkowski, and Dr. Willliam Bains followed up the new observation with an exhaustive analysis of all known processes, other than life, that could have produced phosphine in Venus’ harsh, sulfuric environment. Based on the many scenarios they considered, the team concluded that there is no explanation for the phosphine detected in Venus’ clouds, other than the presence of life or chemical processes that are not yet known to occur on rocky planets.

MIT Initiative press release will follow when it is available (Sept. 14).

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