The researchers presented their study this week in the journal natural astronomy. Their theory is that microbes altered the planet’s atmosphere and thus caused an ice age that wiped them out.
Arguably, this discovery provides bleak perspectives on existence for some. Lead author Boris Souteri says that life – even simple life forms such as microbes – “can often cause their own extinction”. Researcher at the Sorbonne University.
– The results are a bit bleak, but I think it’s also very motivating. Souteri says they are challenging us to reconsider how the biosphere and the planet affect each other.
life below earth
The Sauterey research team assessed the habitability of the surface of Mars about 4 billion years ago. To achieve this, they used climate and terrain models. At that time there was probably a lot of water on the planet. Thus, perhaps the conditions of life were more favorable.
Their guess is that microbes that feed on hydrogen and produce methane as a waste product may have thrived. The idea is that this happened a few centimeters underground. If so, it would provide these microbes with sufficient protection against radiation to allow them to survive.
Wherever there was ice on Mars, these organisms spread in the same way that life spread on Earth in their time.
Mars at that time had a thin atmosphere rich in carbon dioxide. Sotteri’s team believes that the warm, humid climate early in Mars’ history would have reacted strongly as much of the hydrogen disappeared.
Models show that the temperature may have dropped by as much as 200 degrees. Organisms that remained close to the surface then had to bury themselves deeply to try to survive.
On Earth, where nitrogen dominates the atmosphere, the picture was different. The researchers believe that the microbes may have contributed to the stabilization of temperature conditions.
Future models of the Martian climate should take the French study into account, says SETI researcher Kaveh Pahlivan.
Pahlivan recently led another study that concluded that Mars was initially a wet planet. It is believed that warm seas have been there for millions of years. The atmosphere afterwards was denser with a high hydrogen content. Hydrogen may act as a greenhouse gas, before eventually rising into the atmosphere and disappearing into space.
However, the French study, which focuses on the climatic impact of potential microbes, is based on a period when carbon dioxide dominated the Martian atmosphere. Thus, it is not related to the previous period, according to Pahlifan.
—What their study shows, however, is that if there was life on Mars during this period, it would have had a significant impact on the climate, he says.
Search for clues
French scientists also have suggestions on where to look for signs of ancient life that could help confirm their theory.
The Hellas Planeta easy undiscovered area is one. Jezero crater II on the northwest edge of the Isidis Planita Plain region, where the NASA Perseverance spacecraft is currently collecting rock samples. The plan is to be brought to Earth within a decade.
The next item on Boris Souteri’s to-do list is also clear: Searching for signs that microbes are still persistent, deep underground on the red plant.
Is it conceivable that Mars is still inhabited by microorganisms that arose in such a primitive biosphere? And if so – where?
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