Theory and observation for the search for life on exoplanets via atmospheric ‘biosignature gases’ is accelerating, motivated by the capabilities of the next generation of space- and ground-based telescopes. The most observationally accessible rocky planet atmospheres are those dominated by molecular hydrogen gas, because the low density of H2 gas leads to an expansive atmosphere. The capability of life to withstand such exotic environments, however, has not been tested in this context. We demonstrate that single-celled microorganisms (Escherichia coli and yeast) that normally do not inhabit H2-dominated environments can survive and grow in a 100% H2 atmosphere. We also describe the astonishing diversity of dozens of different gases produced by E. coli, including many already proposed as potential biosignature gases (for example, nitrous oxide, ammonia, methanethiol, dimethylsulfide, carbonyl sulfide and isoprene). This work demonstrates the utility of laboratory experiments to better identify which kinds of alien environments can host some form of possibly detectable life.
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We supplied the source data for Figs. 2 and 3, which you can find as supplementary files as well as at https://dspace.mit.edu/handle/1721.1/123824. The other data that support the plots within this paper and other findings of this study are available from the authors on request.
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We thank A. Babbin for use of his laboratory and S. Smirga for assistance. We thank M. Slabicki and C. de Boer for providing us with a sample of yeast Saccharomyces cerevisiae S288C. We also thank J. Petkowska-Hankel for help with Fig. 1 and Z. Zhan for Fig. 4. Seed funding for this work came from the Templeton Foundation Grant ‘The Alien Earths Initiative’, ID 43769. Funding for this work came from the MIT Professor Amar G. Bose Research Grant Program.
The authors declare no competing interests.
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E. coli culture OD measurement data.
Oxygen partial pressures in E. coli experiments
Composite photos of yeast cells in hemocytometer used for cell counting.
Yeast hemocytometer cell counting data.
Oxygen partial pressures in yeast experiments.
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Seager, S., Huang, J., Petkowski, J.J. et al. Laboratory studies on the viability of life in H2-dominated exoplanet atmospheres. Nat Astron 4, 802–806 (2020). https://doi.org/10.1038/s41550-020-1069-4