Mars could have played host to methane spewing microbes within the planet’s early days, scientists say, with the microbes thriving to the purpose of altering the Martian climate.
In a paper published Monday within the journal Nature Astronomy, a team of French and US researchers argue Mars could have hosted microbes in its crust just like the hydrogenotrophic bacteria found on Earth. These terrestrial bacteria devour hydrogen and expel methane gas waste, and were among the many first organisms to live in Earth’s primordial oceans.
“Mars’ crust could have provided a favourable environment for microbial life. The porous brine-saturated regolith would have created a physical space sheltered from ultraviolet and cosmic radiation,” the researchers note within the paper, adding that the quantity of microbes produced on early Mars “might have been as high as within the early Earth’s oceans.”
The researchers used climate modeling to explore the potential habitability of Mars for hydrogenotrophs through the Noachian, a geological period on Mars running from about 4.1 to three.7 billion years ago when the Red Planet could have had abundant surface water and fewer surface ice.
That modeling suggested hydrogenotrophs could have thrived within the soil, but that presents a catch — although the microbes would have been expelling methane, a greenhouse gas, they’d have been eating hydrogen, which also has a warming effect. In as little as 100,000 to 500,000 years, the bacterial activity could have modified the Martian climate, making a cooling effect which will have driven global average temperatures from around 60 degrees Fahrenheit to 10 degrees below zero.
This cool would have in turn created more ice, driving the microbes further underground.
It’s a really different story than on the early Earth, where hydrogenotrophs actually helped maintain the worldwide temperature.
The important thing difference was within the initial atmospheric conditions, the researchers notes. On Mars, with its carbon dioxide dominated atmosphere, hydrogen was a stronger greenhouse gas than methane, whereas in Earth’s nitrogen dominated atmosphere, methane was a stronger greenhouse gas.
Could any of the traditional hydrogenotrophic microbes on Mars still exist there, deep in its crust? The researchers argue it’s possible, and that, “one of the best validation of our predictions would come from the invention on present-day Mars of methanogenic life descending from the early metabolism modelled here.”
But such lifeforms would likely have needed to transition away from consuming hydrogen, perhaps evolving into extremophiles subsisting on chemical reactions —chemotrophs — or the byproducts of radioactive decay beneath the Martian surface.
“Deep chemotrophic ecosystems exist on Earth,” the researchers write within the paper. “An extant ecosystem on modern Mars is likely to be of that sort.”
Furthermore, they note, these descendants of early hydrogenotrophs might still expel methane waste gas, which might explain the strange, intermittent measurements of methane gas within the Martian atmosphere observed by scientists.
Scientists may get their answer to such questions inside the decade.
Nasa’s Perseverance Rover is currently collecting samples of Martian rock and regolith and caching them for later pick. Nasa and the European Space Agencys’ Mars Sample Return Mission will collect those samples and produce them to Earth for study in innovative laboratories equipped to reply once and for all of the query of whether there’s, or ever has been, life on Mars.