Early life on Mars may have wiped out early life on Mars, new study suggests

(ORDO NEWS) — Life could have disappeared on early Mars. This is not as absurd as it seems; something like what happened on Earth.

But life evolved and persisted on Earth, but not on Mars.

Evidence shows that Mars was once warm and humid, and the atmosphere. During the ancient Noah period, between 3.7 billion and 4.1 billion years ago, Mars also had surface water. If so, Mars could be habitable (though that doesn’t necessarily mean it was habitable).

A new study shows that early Mars may have been hospitable to a type of organism that thrived under extreme conditions. environment here on earth.

Methanogens live in places like hydrothermal vents on the ocean floor, where they convert the chemical energy of the environment and release methane as waste. The study shows that methanogens could have thrived underground on Mars.

The study is titled “Early Martian Habitability and Global H2-Based Methanogen Cooling”. It is published in the journal Nature Astronomy , and the senior authors are Régis Ferrière and Boris Soterey.

Ferrier is a professor in the Department of Ecology and Evolutionary Biology at the University of Arizona, and Sautres is a former postdoctoral fellow in Ferrier’s group now at the Sorbonne.

“Our study shows that underground early Mars could very likely have been habitable for methanogenic microbes,” Ferrier said in a press release. However, the authors make it clear that they are not claiming that life definitely existed on the planet.

The paper says the microbes could have thrived in the porous, salty rock, which shielded them from ultraviolet radiation and cosmic rays. The underground environment also provided a diffuse atmosphere and moderate temperatures, which allowed methanogens to persist.

The researchers focused on hydrogenotrophic methanogens, which take up H 2 and CO 2 and produce methane as a waste product. This type of methanogenesis was one of the earliest types of metabolism to appear on Earth. However, its“…viability on early Mars has never been quantified,” the paper says..

With respect to this study, there is a critical difference between ancient Mars and Earth. On Earth, most of the hydrogen is bound to water molecules, and very few are on their own. But on Mars there was a lot of it in the atmosphere of the planet.

This hydrogen could have been the source of energy needed for the early methanogens to thrive. That same hydrogen would help keep the heat in Mars’ atmosphere, making the planet habitable.

“We think Mars might have been a little colder than Earth at the time, but not as cold as it is now. now that the average temperature is likely to hover above the freezing point of water,” Ferrier said. porous crust soaked with liquid water, which probably formed lakes and rivers, perhaps even seas or oceans.

On Earth, water is either salty or fresh. But on Mars, this distinction may not have been necessary. Instead, all the water was salty, according to spectroscopic measurements of Martian surface rocks.

The research team used models of the climate, crust, and atmosphere of Mars to estimate methanogens on ancient Mars. They also used the ecological community model of terrestrial microbes that metabolize hydrogen and carbon.

By working with these ecosystem models, the researchers were able to predict whether methanogen populations could survive. But they went further; they were able to predict what effect these populations had on the environment.

“After we created our model, we put it to work in the Martian crust figuratively speaking,” said Boris Soteri, the first author of the article.

“This allowed us to assess how plausible a Martian underground biosphere would be. And if such a biosphere existed, how would it change the chemical composition of the Martian crust, and how would these processes in the crust affect the chemical composition of the atmosphere.

“Our goal was to create a model of the Martian crust with its mixture of rocks and salt water, let gases from the atmosphere diffuse into the earth, and see if methanogens could live with it,” Ferrier said. “And the answer is, generally speaking, yes, these microbes could make a living in the planet’s crust.”

The question was how deep would you have to go to find them? According to the researchers, it’s a matter of balance.

Although the atmosphere contained large amounts of hydrogen and carbon that organisms could use for energy, the surface of Mars was still cold. Not frozen like it is today, but much colder than modern Earth.

Microorganisms would benefit from warmer temperatures underground, but the deeper you go, the less hydrogen and carbon is available.

“The problem is that even on early Mars it was still very cold on the surface, so microbes had to go deeper into the crust to find a habitable temperature,” Soteri said.

“The question is, how deep does biology have to go to find the right compromise between temperature and the presence of molecules from the atmosphere necessary for their growth? We found that the microbial communities in our models would be happiest within a few hundred meters.”

They would have remained in the upper part of the earth’s crust for a long time. But as the microbial communities persisted by taking in hydrogen and carbon and releasing methane, they would change the environment.

The team modeled all of the above and underground processes and their impact. each other. They predicted the resulting climate feedback and how it changed the Martian atmosphere.

The team says that over time, methanogens would initiate global climate cooling as they changed the chemical composition of the atmosphere. Salt water in the Earth’s crust would freeze to greater and greater depths as the planet cooled.

This cooling would eventually render the surface of Mars uninhabitable. When the planet cooled, the organisms would go deeper underground, away from the cold.

But the pores in the regolith would clog up with ice, preventing the atmosphere from reaching these depths, and depriving methanogens of energy.

“According to our results, the Martian atmosphere would have been completely changed by biological activity very quickly, within a few tens or hundreds of thousands of years,” Sauteri said. “By removing hydrogen from the atmosphere, microbes have dramatically cooled the planet’s climate.”

Early life on Mars may have wiped out early life on Mars new study suggests 1
Each row represents a freezing point for a particular type of brine. The orange scale represents height. The superimposed areas shaded in white correspond to the probability of the presence of ice on the surface

Result? Extinction.

“The problem that these microbes would then face was that the atmosphere of Mars had practically disappeared, completely thinned, so their energy source was gone, and they would have to look for an alternative energy source,” Sauterey said.

“Besides, the temperature would drop significantly, and they would have to go deeper into the crust. At this point it is very difficult to say how long Mars would have remained habitable.”

The researchers also identified locations on the surface of Mars where future missions have the best chance of finding evidence of ancient life on the planet.

“Near-surface populations might have been the most productive, maximizing the likelihood of retaining biomarkers in detectable amounts,” the authors write in their paper. “The first few meters of the Martian crust are also the most accessible to study, given the technology currently used on Martian rovers.”

According to the researchers, the Hellas Plain is the best place to look for evidence of this early underground life because it remained free of ice.

Unfortunately, this region is home to powerful dust storms and is not suitable for rover exploration. According to the authors, if human explorers ever visit Mars, then Hellas Planitia would be the perfect place to explore.

Life on ancient Mars is no longer a revolutionary idea. So the more interesting part of this study might be how early life changed the environment. This happened on Earth and led to the development of more complex life after the Great Oxygenation Event (GOE).

The early Earth was also inhabited by simple life forms. But the Earth was different; organisms have developed a new way of using energy.

There was no oxygen in the Earth’s early atmosphere, and the first inhabitants of the Earth thrived in its absence. Then came cyanobacteria, which use photosynthesis for energy and produce oxygen as a by-product.

Cyanobacteria loved oxygen, but the first inhabitants of the Earth did not. The cyanobacteria grew in mats that created an area of ​​oxygenated water around them in which they thrived.

Eventually, cyanobacteria oxygenated the oceans and atmosphere until Earth became toxic to other life. Methanogens and other early life forms on Earth can’t handle oxygen.

Scientists don’t exactly call the death of all these primitive organisms extinction, but the word is close. Some ancient microbes or their descendants survive on modern Earth, driven into an oxygen-poor environment.

But it was Earth. On Mars, there was no evolutionary leap into photosynthesis or anything that would lead to a new way of getting energy. Eventually Mars cooled, froze and lost its atmosphere. Mars is now dead?

Perhaps Martian life has taken refuge in isolated places in the planet’s crust.

A 2021 study used simulations to show that there could be a source of hydrogen in the subsurface. The crust of Mars, which replenishes itself.

The study showed that radioactive elements in the Earth’s crust can split water molecules by radiolysis, making hydrogen available to methanogens. Radiolysis allowed isolated communities of bacteria to persist in water-filled cracks and pores in the earth’s crust for millions, perhaps billions of years.

And the Deep Carbon Observatory has found that life hidden in the earth’s crust contains up to 400 times the mass of carbon of all humans. The DCO also found that the deep subsurface biosphere is nearly twice the volume of the world’s oceans.

Could life still exist in the Martian crust, feeding on hydrogen produced by radiolysis? There are mysterious detections of methane in the atmosphere that are still unexplained.

Many scientists believe that the interior of Mars is the most likely place in the solar system for life, other than Earth, of course. (Sorry, Europe.) Maybe, and maybe one day we will find it.


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