June 10, 2023
Early life on Mars may have wiped out early life on Mars, a new study suggests

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

Life may have been extinct on early Mars. This is not as absurd as it sounds. that’s how it happened on Earth.

But life on Earth evolved and persisted, while on Mars, it did not.

Evidence suggests 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 this does not necessarily mean that it was inhabited.)

A new study suggests that early Mars may have been host to a type of organism that thrives in extreme environments here on Earth. Methanogens live in places like hydrothermal vents on the ocean floor, where they convert chemical energy from their environment and release methane as waste. The study suggests that methanogens may have thrived underground on Mars.

The study is “Early habitability of Mars and global cooling by H2-based methanogens.” It is published on Astronomy of Nature, and senior authors are Regis 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 now at the Sorbonne.

“Our study shows that subsurface, early Mars would very 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 paper says the microbes would have thrived in the porous, salty rock that protected them from UV and cosmic rays. The subterranean environment would also provide a diffuse atmosphere and moderate temperature that allowed methanogens to persist.

The researchers focused on hydrotrophic methanogens, which recruit H2 and CO2 and produce methane as waste. This type of methanogenesis was one of the first metabolisms to develop on Earth. However, its “…sustainability on early Mars 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 by itself. But on Mars, it was abundant in the planet’s atmosphere.

This hydrogen could be the energy supply early methanogens need to thrive. The same hydrogen would help trap heat in the Martian atmosphere, keeping the planet habitable.

“We think Mars may have been a bit cooler than Earth at the time, but not as cold as it is now, with average temperatures probably hovering above the freezing point of water,” Ferrière said.

“While today’s 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 likely 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 salty, according to spectroscopic measurements of Martian surface rocks.

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

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

“Once we built our model, we put it to work on the Martian crust – figuratively speaking,” said the paper’s first author, Boris Sauterey.

“This allowed us to assess how plausible a Martian subsurface biosphere would be. And if such a biosphere existed, how it would have modified the chemistry of the Martian crust and how those 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 the mixture of rock and salt water, let the gases from the atmosphere diffuse into the soil, and see if methanogens could live on it,” Ferrière said. “And the answer is, generally speaking, yes, these microbes could have made a living in the crust of the planet.”

The question became, how deep would you have to go to find it? It’s a matter of balance, according to the researchers.

While the atmosphere held plenty 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 have benefited from the higher temperatures in the soil, but the deeper you go, the less hydrogen and carbon is available.

“The problem is that even early on Mars, it was still very cold on the surface, so microbes would have to go deeper into the crust to find habitable temperatures,” Sauterey said.

“The question is, how deep does biology need to go to find the right trade-off between temperature and the availability of molecules from the atmosphere that they needed to grow? We found that the microbial communities in our models would be happiest in the upper hundreds of meters. “

They would stay nestled in the upper crust for a long time. But as the microbial communities persisted, taking in hydrogen and carbon and releasing methane, they would have changed the environment.

The team modeled all the above and below ground processes and how they would have affected each other. They predicted the resulting climate feedback and how it changed the Martian atmosphere.

The team says that over time, methanogens would have initiated global climate cooling as they changed the chemical composition of the atmosphere. The salty water in the crust would have frozen to greater and greater depths as the planet cooled.

This cooling would eventually make the Martian surface uninhabitable. As the planet cooled, organisms would have been driven further underground, away from the cold.

But the porosity in the regolith would have been plugged by ice, preventing the atmosphere from reaching these depths and starving the 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,” Sauterey said. “By removing hydrogen from the atmosphere, microbes would have dramatically cooled the planet’s climate.”

Each row represents the freezing point for a different type of brine. The orange color scale represents elevation. Overlapping areas with white shading correspond to the possibility of surface ice. (Boris Sauterey and Regis Ferrière)

The result? Disappearance.

“The problem these microbes would have is that the Martian atmosphere basically disappeared, completely thinned out, so their energy source would be gone and they would have to find an alternative energy source,” Sauterey said.

“Furthermore, the temperature would have dropped significantly and they would have had to go much deeper into the crust. At the moment, it is very difficult to say how long Mars would have remained habitable.”

The researchers also identified spots 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 be the most productive, thus maximizing the likelihood of maintaining biomarkers in detectable amounts,” the authors write in their paper. “The first few meters of the Martian crust are also the most easily accessible for exploration, given the technology currently used in Mars 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 hosts severe dust storms and is unsuitable 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 around for a long time. So the most interesting part of this research may be how early life changed its 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 populated by simple life forms. But Earth was different. organisms evolved a new pathway to harness energy. There was no oxygen in Earth’s early atmosphere, and Earth’s first inhabitants thrived in its absence. Next came cyanobacteria, which use photosynthesis for energy and produce oxygen as a byproduct.

Cyanobacteria liked oxygen and Earth’s first inhabitants 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 Earth life cannot handle oxygen.

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

But this was Earth. On Mars, there was no evolutionary leap in photosynthesis or anything else that led to a new way of obtaining energy. Eventually, Mars cooled and froze and lost its atmosphere. Is Mars dead now?

It is possible that Martian life took refuge in isolated locations in the planet’s crust.

A 2021 study used modeling to show that there may be a source of hydrogen in the Martian crust, one that is replenished. The study showed that radioactive elements in the crust could split water molecules by radiolysis, making hydrogen available to methanogens. Radiolysis allowed isolated communities of bacteria in water-filled cracks and pores in the Earth’s crust to persist for millions, possibly 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 the volume of the world’s oceans.

Could there still be life in the Martian crust, feeding on hydrogen created by radiolysis? There are puzzling detections of methane in the atmosphere that are still unexplained.

Many scientists believe that the subsurface of Mars is the most likely place in the Solar System to host life, other than Earth, of course. (Sorry, Europe.) Maybe it is, and maybe we’ll find it one day.

This article was originally published by Universe Today. Read the original article.

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