We’ll probably look at the gases in its atmosphere the first time we look for signs of life on a planet circling another star (an exoplanet). As the number of known Earth-like planets rises, we may soon discover gases associated with life on Earth in the atmosphere of an exoplanet.
But what if extraterrestrial life has a chemical that differs from ours? Expanding our search beyond planets like our own to include those with a hydrogen atmosphere, according to a recent research published in Nature Astronomy, boosts our odds of finding evidence of life utilizing atmospheres.
The atmosphere of an exoplanet may be studied when it passes in front of its star. The star’s light must pass through the planet’s atmosphere to reach us during transit, and part of it is absorbed.
The gases that make up the atmosphere are revealed by looking at the star’s spectrum (light split down by wavelength) to determine what light is absent due to the transit. One of the long-delayed James Webb Space Telescope’s missions is to document extraterrestrial atmospheres.
The presence of biological activity is one of the most fundamental interpretations of an environment with a chemical makeup that differs from what we anticipate. This is the current state of affairs on the planet. Methane (CH4), which naturally combines with oxygen to produce carbon dioxide, is found in our planet’s atmosphere. Biological activity, on the other hand, guarantees that there is never a shortage of methane.
Another way to look at it is that if photosynthetic bacteria hadn’t freed oxygen from carbon dioxide during the so-called “great oxygenation event” 2.4 billion years ago, oxygen would not exist at all.
Take a peek outdoors of locations with a lot of oxygen.
The authors of the new study propose that we begin looking at planets larger than Earth that have hydrogen-dominated atmospheres. There may be no free oxygen present since hydrogen and oxygen are such a combustible mix.
In 1937, fire destroyed the hydrogen-filled Hindenberg airship. On a planet with an oxygen-free hydrogen atmosphere, such a conflagration would be impossible. Murray Becker of the Associated Press contributed to this photo.
Hydrogen is the universe’s lightest molecule, and it can quickly escape into space. A rocky planet with enough gravity to support a hydrogen atmosphere would have to be a “super-Earth” with a mass of two to ten times Earth’s.
The hydrogen might have emerged from a chemical process involving iron and water, or it could have come directly from the gas cloud in which the planet formed.
The density of a hydrogen-dominated atmosphere falls 14 times slower as you rise than a nitrogen-dominated atmosphere like the Earth’s.
As a result, the atmosphere of the planet has a 14-fold larger envelope, as observed in spectrum data. We’d have a higher chance of directly seeing such an environment with an optical telescope if the environment had more dimensions.
In the lab, hydrogen is breathed.
The researchers utilized laboratory studies to show that E. coli bacteria (which may be found in billions in your intestines) can survive and flourish in a hydrogen-only environment. They were able to show the same effect using a variety of yeast.
While intriguing, this contributes nothing to the case that life may thrive in a hydrogen-rich environment. Many deep-sea bacteria already exist by metabolizing hydrogen, and there is even a multicellular species that spends its whole life on the Mediterranean’s bottom in an oxygen-free habitat.
Spinoloricus is a tiny multicellular species that does not appear to require oxygen to survive. The scale bar measures 50 micrometers in length.
It’s quite unlikely that the Earth’s atmosphere, which began without oxygen, ever contained more than 1% hydrogen. Rather than mixing oxygen and carbon to make carbon dioxide, early life may have had to metabolize by combining hydrogen and carbon to generate methane.
Gases that have a distinct biosignature.
The study did, however, provide a noteworthy result. According to the researchers, when E. coli products are exposed to hydrogen, they produce a “astonishing variety” of gases.
In a hydrogen environment, several of these, such as dimethylsulfide, carbonyl sulfide, and isoprene, may be detectable “biosignatures.” This increases the chances of finding life on an extrasolar planet, but only if we know what to look for.
However, metabolic activities that use hydrogen are inefficient compared to those that use oxygen. Astrobiologists, on the other hand, believe that hydrogen-breathing life is a well-established idea. Some logically based science fiction, like as David Brin’s Uplift trilogy, has featured sentient hydrogen breathers.
According to the authors of the study, molecular hydrogen can act as a greenhouse gas in large amounts. This might maintain the surface of a planet warm enough for liquid water, and so surface life, for longer than it would otherwise.
The authors make no mention of the possibility of life on giant gas planets such as Jupiter. Nonetheless, by widening the pool of habitable planets to include super-Earths with hydrogen-rich atmospheres, scientists have effectively doubled the number of worlds we may examine in search of the first signals of extraterrestrial life.
