Journal Article

Laboratory studies on the viability of life in H2-dominated exoplanet atmospheres

Seager, S., Petkowski, J. J., Pajusalu, M., Huang, J.

2020

Overview

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 H 2 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 H 2 -dominated environments can survive and grow in a 100% H 2 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. Escherichia coli bacteria and yeast cultures (representative prokaryotes and eukaryotes) have been tested under laboratory conditions in a 100% H 2 atmosphere. They can reproduce normally, with lower growth rates, producing a range of biosignature gases. Exoplanets with a H 2 -dominated atmosphere might thus not be totally hostile to some forms of life.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/33 / 639/33/34 / 704/445 / Astronomy / Astrophysics and Cosmology / Atmosphere / Carbonyl compounds / E coli / Laboratories / Microorganisms / Nitrous oxide / Physics / Physics and Astronomy / Yeast