Planetary science: Life under a hydrogen atmosphere

Microorganisms can survive and grow in a 100% hydrogen atmosphere, according to a paper published in Nature Astronomy this week. The findings suggest life could potentially thrive in a much broader variety of exoplanetary environments than is usually considered.

Rocky exoplanets more massive than Earth, can retain a significant amount of hydrogen in their atmosphere. Such hydrogen-rich atmospheres are likely to be more extended than Earth-like ones, making the exoplanet atmospheres easier to detect. High abundances of hydrogen are not usually considered conducive to life, but research on the viability of life in these environments is lacking.

Sara Seager and colleagues conducted laboratory-based growth experiments on Escherichia coli and yeast, which are representative of prokaryote and eukaryote microorganisms, respectively. The authors exposed cultures of E. coli and yeast to a 100% hydrogen atmosphere. They found that both organisms could reproduce normally, albeit at lower rates than in air. E. coli reproduced around two times slower, while yeast was around 2.5 times slower, which was due to the lack of oxygen, the authors argue.

Microorganisms like E. coli produce a great variety of gases, including potential biosignature gases, which could build up in sizeable abundances and eventually become detectable.