Life could have faded away at the beginning of March. It’s not as absurd as it sounds; it’s a bit like what happened on Earth.
But life on Earth evolved and persisted, whereas on Mars it didn’t.
Evidence shows that Mars was once hot and humid and had an atmosphere. In the ancient Noachian period, between 3.7 billion and 4.1 billion years ago, Mars also had surface water. If this is correct, Mars may have been habitable (although that doesn’t necessarily mean it was inhabited.)
Early Mars may have been hospitable to a type of organism that thrives in extreme environments here on Earth, a new study shows. Methanogens live in places like hydrothermal vents on the ocean floor, where they convert chemical energy from their surroundings and release methane as a waste product. The study shows that methanogens may have thrived underground on Mars.
The study is “early Mars habitability and global cooling by H2-based methanogens”. It is published in natural astronomy, and the main authors are Régis Ferrière and Boris Sauterey. Ferrière is a professor in the Department of Ecology and Evolutionary Biology at the University of Arizona, and Sauterey is a former postdoctoral fellow in Ferrière’s group who is now at the Sorbonne.
“Our study shows that underground, early Mars would most likely have been habitable for methanogenic microbes,” Ferrière said in a press release. However, the authors are clear that they are not saying that life definitely existed on the planet.
The article states that the microbes would have thrived in the porous, brackish rock that sheltered them from UV rays and cosmic rays. The subterranean medium would also have provided a diffuse atmosphere and moderate temperature allowing methanogens to persist.
The researchers focused on hydrogenotrophic methanogens, which take up H2 and co2 and produce methane as waste. This type of methanogenesis was one of the first metabolisms to evolve on Earth. However, its “…viability on early March has never been quantitatively assessed,” the paper says.
So far.
There is a critical difference between ancient Mars and Earth regarding this research. On Earth, most hydrogen is bound to water molecules, and very little is alone. But on Mars, it was abundant in the planet’s atmosphere.
This hydrogen could have been the energy supply that the first methanogens needed to thrive. That same hydrogen would have helped trap heat in Mars’ atmosphere, keeping the planet habitable.
“We think Mars was maybe a bit colder than Earth then, but not as cold as it is now, with average temperatures most likely hovering above the freezing point of the planet. water,” Ferriere said.
“While present-day Mars has been described as an ice cube covered in dust, we imagine early Mars as a rocky planet with a porous crust, soaked in liquid water that probably formed lakes and rivers, perhaps even seas or oceans.”
On Earth, water is either salt water or fresh water. But on Mars, this distinction may not have been necessary. Instead, all the water was brackish, according to spectroscopic measurements of Martian surface rocks.
The research team used models of the climate, crust and atmosphere of Mars to assess methanogens on ancient Mars. They also used an ecological community model of Earth-like microbes that metabolize hydrogen and carbon.
By working with these ecosystem models, the researchers were able to predict whether methanogenic populations were able to survive. But they went further; they were able to predict the effect of these populations on their environment.
“Once we produced our model, we implemented it in the Martian crust – figuratively speaking,” said the paper’s first author, Boris Sauterey.
“This allowed us to assess the plausibility of a Martian subterranean biosphere. And if such a biosphere existed, how it would have changed the chemistry of the Martian crust, and how these processes in the crust would have affected the chemical composition of the atmosphere. .”
“Our goal was to make a model of the Martian crust with its mix of rock and salt water, let gases from the atmosphere diffuse into the ground, and see if methanogens could live with that,” said Ferriere. “And the answer is, generally speaking, yes, these microbes could have made their living in the earth’s crust.”
The question became, how deep should you go to find it? It’s a question of balance, according to the researchers.
While the atmosphere contained abundant hydrogen and carbon that organisms could have used to produce energy, the surface of Mars was still cold. Not frozen like today, but much colder than modern Earth.
The microorganisms would have benefited from the warmer temperatures underground, but the deeper you go, the less hydrogen and carbon there is available.
“The problem is that even in early Mars it was still very cold on the surface, so the microbes would have had to penetrate deeper into the crust to find habitable temperatures,” Sauterey said.
“The question is how far should biology go to find the right trade-off between temperature and the availability of molecules from the atmosphere that they need to grow? We found that the microbial communities in our models would have been happier in the upper few hundred meters.”
They would have remained nested in the upper crust for a long time. But as the communities of microbes persisted, absorbing hydrogen and carbon and releasing methane, they would have changed the environment.
The team modeled all the processes above and below ground and how they would have influenced each other. They predicted the resulting climate feedback and how it changed the atmosphere of Mars.
The team claims that over time, methanogens may have initiated global climate cooling by altering the chemical composition of the atmosphere. The brackish water in the crust would have frozen to greater and greater depths as the planet cooled.
This cooling would have ultimately made the surface of Mars uninhabitable. As the planet cooled, organisms would have been pushed further underground, away from the cold.
But the porosity of the regolith would have been clogged with ice, preventing the atmosphere from reaching these depths and starving the methanogens of energy.
“According to our results, the atmosphere of Mars would have been completely modified by biological activity very quickly, within a few tens or hundreds of thousands of years,” Sauterey said. “By removing hydrogen from the atmosphere, the microbes would have significantly cooled the planet’s climate.”
The result? Extinction.
“The problem these microbes would then have faced is that the atmosphere of Mars was pretty much gone, completely thinned out, so their source of energy would have disappeared and they would have had to find another source of energy,” he said. said Sauterey.
“Furthermore, the temperature would have dropped significantly, and they would have had to sink much deeper into the crust. At this time, it is very difficult to say how long Mars would have remained habitable.”
The researchers also identified places on the Martian surface where future missions have the best chance of finding evidence of the planet’s ancient life.
“Populations near the surface would have been the most productive, thus maximizing the likelihood of biomarkers being retained in detectable amounts,” the authors write in their paper. “The first meters of the Martian crust are also the most easily accessible to exploration given the technology currently on board Martian rovers.”
According to the researchers, Hellas Planitia is the best place to look for evidence of this early subterranean life because it remained ice-free. Unfortunately, this region is home to powerful dust storms and not suitable for rover exploration. According to the authors, if human explorers ever visit Mars, then Hellas Planitia is an ideal exploration site.
Life on ancient Mars is no longer a revolutionary idea, and hasn’t been for a long time. So the most interesting part of this research might be how life has changed its environment. This happened on Earth and led to the development of more complex life after the Great Oxygenation Event (GOE).
Early Earth was also inhabited by simple life forms. But Earth was different; organisms have developed a new way to harness energy. There was no oxygen in Earth’s early atmosphere, and Earth’s first inhabitants thrived in its absence. Then came the cyanobacteria, which use photosynthesis as an energy source and produce oxygen as a byproduct.
Cyanobacteria loved oxygen, unlike Earth’s first tenants. The cyanobacteria grew into mats that created a region of oxygenated water around them in which they thrived.
Eventually, the cyanobacteria oxygenated the oceans and atmosphere until the Earth became toxic to other life forms. Methanogens and other early life on Earth cannot handle oxygen.
Scientists don’t quite call the death of all these primitive organisms an extinction, but the word comes close. Some ancient microbes or their descendants survive on modern Earth, grown in oxygen-poor environments.
But it was Earth. On Mars, there was no evolutionary leap to photosynthesis or anything else that led to a new way of acquiring energy. Eventually Mars cooled and froze and lost its atmosphere. Is Mars dead now?
It is possible that Martian life found refuge in isolated places in the Earth’s crust.
A 2021 study used modeling to show that there could be a source of hydrogen in the crust of Mars, a source that is being replenished. The study showed that radioactive elements in the crust could break down water molecules by radiolysis, making hydrogen available for methanogens. Radiolysis has allowed isolated communities of bacteria in water-filled fissures and pores in the earth’s crust to persist for millions, if not billions of years.
And the Deep Carbon Observatory found that life buried in the Earth’s crust contains up to 400 times the mass of carbon of all humans. The DCO also found that the deep underground biosphere is almost twice as large as the world’s oceans.
Could there still be life in the crust of Mars, feeding on hydrogen created by radiolysis? There are puzzling detections of methane in the atmosphere that are still unexplained.
Many scientists believe that Mars’ subsurface is the most likely place to support life in the solar system, other than Earth, of course. (Sorry, Europa.) Maybe so, and maybe we’ll find it someday.
This article was originally published by Universe Today. Read the original article.
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