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Some microbes can not only survive, but also replicate in an atmosphere made entirely of hydrogen. These important findings suggest that life could appear in a variety of extraplanetary environments that scientists previously discounted.
Life never ceases to amaze us
Billions of years ago, Earth had very small amounts of hydrogen in its primordial atmosphere, down to about 0.1%. Molecular hydrogen persisted in the atmosphere for hundreds of millions of years until the Great Oxidation Event.
Today, the little hydrogen that is produced is quickly consumed by microorganisms, oxidized in the atmosphere or lost in space.
Astrophysicists believe that many rocky exoplanets, super-terrestrial exoplanets (an extrasolar planet with a mass higher than Earth, but substantially below the ice giants of the Solar System), and even rocky planets (planets outside the solar system) They can have a hydrogen-abundant atmosphere under certain conditions.
Some examples of such planets include Trappist-1 d, e, f, and g, and LHS 1132b.
Given that it seems likely that there are some hydrogen-dominated atmospheres beyond our solar system, and considering that such rocky planets are easier to detect than those with nitrogen or CO2-dominated atmospheres, MIT researchers wanted to investigate the viability of life. on such planets
The research team performed growth experiments in a bioreactor system on two species of microorganisms: Escherichia coli and the yeast Saccharomyces cerevisiae.
These simple organisms are representative of prokaryotic and eukaryotic microorganisms, respectively.
“We note that we chose a 100% H2 gas environment as a control. Actual H2-dominated atmospheres will always have other gaseous components that are products of planetary geology or atmospheric photochemistry. Furthermore, rocky planets will have to be colder than Earth, have a more massive surface gravity than Earth, and / or a replenishment mechanism to maintain an atmosphere dominated by H2, “the authors wrote in their study.
Surprisingly, both organisms could reproduce normally in a 100% hydrogen atmosphere. However, they do so at slower speeds than in oxygenated air.
E. coli it reproduced twice as slowly, while the yeast was about 2.5 orders of magnitude slower. The authors argue that a lack of oxygen is responsible for the reduced replication rate.
E. coli It also synthesizes an impressive number of volatile molecules that can be detected on worlds light years from Earth.
“That an organism as simple as E. coli, and a single species, has a sufficiently diverse metabolic machinery capable of producing a range of gases with useful spectral characteristics is very promising for the detection of biosignature gases in exoplanets. While most gases are produced in small quantities on Earth, there are exoplanet environments where gases if produced in large quantities could accumulate, “the authors wrote in their article published today in the journal. Astronomy of nature.
