Research published in Nature Astronomy has revealed that microbes can survive and thrive in atmospheres that are dominated by hydrogen, an environment very different from Earth’s nitrogen and an oxygen-rich atmosphere. Hydrogen is a much lighter gas than nitrogen or oxygen, and an atmosphere rich in hydrogen would extend much further upwards compared to a rocky planet. Therefore, this atmosphere might be easier to detect and study with powerful telescopes, compared to planets with more compact atmospheres, like our own planet.
The results of the study, led by MIT astronomer Sara Seager, show that simple life forms could inhabit planets with hydrogen-rich atmospheres, suggesting that once next-generation telescopes, such as NASA’s James Webb space telescope launch, astronomers could have state of the art tools that will allow them to look for alien life on distant planets whose atmosphere is dominated by hydrogen.
Seager and her colleagues observed how microbes survived and thrived in a laboratory-created atmosphere dominated by hydrogen.
“There’s a diversity of habitable worlds out there, and we have confirmed that Earth-based life can survive in hydrogen-rich atmospheres,” Seager explained.
“We should definitely add those kinds of planets to the menu of options when thinking of life on other worlds, and actually trying to find it.”
To understand more about potentially habitable worlds that are very different from what Earth is like today, we can look at what a primitive Earth looked like millions of years ago. Back then, the atmosphere looked very different from the air we breathe today. The young planet had not yet received oxygen and was made up of a gas soup, which included carbon dioxide, methane, and a very small fraction of hydrogen.
Hydrogen gas remained in the atmosphere for possibly billions of years, until what is known as the Great Oxidation Event, and the gradual accumulation of oxygen.
The small amount of hydrogen that remains today is consumed by certain ancient lines of microorganisms, including methanogens, organisms that live in extreme climates, such as deep within the ice, or within the desert floor, and gobble up hydrogen, along with carbon dioxide, to produce methane.
To find out more what kind of alien lifeforms we may encounter, studying organisms such as methanogens is of great importance. Scientists routinely study the activity of methanogens grown in laboratory conditions with 80 percent hydrogen. But there are very few studies exploring the tolerance of other microbes to hydrogen-rich environments.
“We wanted to demonstrate that life survives and can grow in a hydrogen atmosphere,” revealed Seager, whose study offers evidence that alien life does not necessarily have to be similar to us.
For all we know, there are lifeforms on a distant exoplanet that need elements that are hazardous for us in order to survive. Since we haven’t yet found confirmation of life on another cosmic body besides Earth, we can’t possibly know that kind of life forms exist in the universe, all we can do at this time is experiment and simulate.