How life on Earth could help us find life on Mars

In our continuing search for another life in the universe, one place has always seemed promising: Mars. It is a rocky planet like Earth, orbiting the same star, and at a distance where water could have been present on the planet.

Today, however, Mars is an arid wasteland. Any water that once had on its surface hundreds of millions of years ago no longer exists, while its atmosphere is a thin layer of the thickest barrier it ever could have been. But could the planet have harbored life in the past, and is there a chance that some life on Mars may have survived today?

While we still can’t answer those questions, we are closer than ever to finding out. And with a series of new missions on the horizon, new clues begin to emerge.

Deserts

On Earth, life survives in a wide variety of places, from the Sahara deserts to the frozen glaciers of Antarctica. The surface of Mars today has similarities to some of these places, so if we can find life in these places on Earth, perhaps it is also on Mars.

Dr. Dirk Schulze-Makuch from the Technical University of Berlin, Germany coordinated the Habitability of Martian Environments (HOME) project, which studied the soil collected from the Atacama Desert in South America and examined which microbes were present, if the would have. The results showed that life was fascinatingly resilient.

“We show that even in the hyperharid nucleus, there is still active microbial life,” said Dr. Schulze-Makuch. “We found several survival mechanisms. For example, some microbes use water directly from the atmosphere, so they don’t need rain.”

The team also created different soils and salty brines that mimicked some of the conditions on Mars. By introducing microbes into these analogues of Mars, they could determine what kind of life could survive below the surface of Mars.

“We were primarily interested in Extremophiles (life that survives in extreme places on Earth),” said Dr. Schulze-Makuch. “For the brine experiments we used planococcus halocryophilus (a microbe that can live in very salty and very cold conditions). We found that it had a very high tolerance.”

While we can mimic the conditions on Mars, however, we can’t exactly replicate them. The surface of Mars has much higher levels of radiation than anywhere on Earth, and there is much less water available on Mars than in the driest deserts on Earth.

“There are many microbes that can survive amazingly in conditions that are getting very close to Mars,” said Dr. Schulze-Makuch. “But you would have to test on Mars to be absolutely sure.”

Water

Understanding how much water there was on Mars in the past is crucial to understanding its potential habitability. We know that on Earth, almost anywhere we find water we find life. So if Mars was once much wetter than it is today, the chances of habitability increase considerably.

We have found evidence of ancient water on Mars in a variety of places. NASA’s Curiosity rover may have found an ancient lake bed, while the northern hemisphere of Mars appears to have once contained a large ocean. Now scientists want to take these studies even further.

Dr. Alberto Fairén of the Spanish Center for Astrobiology in Madrid, Spain, coordinates a project called MarsFirstWater. This project aims to calculate how much water could have been on Mars in its first billion years, whether it was liquid water or ice, how long it was there, and where it was.

Using data from past, present and future Mars missions, both on Earth and on Mars itself, such as NASA’s upcoming Perseverance rover, which will launch in July 2020, and Europe’s Rosalind Franklin rover planned for launch. in 2022, the project aims to Rebuild and map the surface of ancient Mars like never before.

“Between 4.5 and 3.5 billion years ago, Mars is believed to have had an active surface hydrosphere that included glaciers, rivers, lakes, deltas, and perhaps even a hemispheric ocean the size of the Mediterranean Sea,” said Dr. Fairén.

The early emerging image from Mars, he says, suggests that his summers were similar to winters in Iceland and his winters were similar to winters in Antarctica.

Stripped off

An earlier study by Dr. Fairén, called IcyMARS, concluded that ancient Mars may have been colder than people expected, but still humid enough to be habitable. At some point in its history, this water was stripped from Mars when the planet’s core cooled for unknown reasons, and its atmosphere was blown away by the solar wind.

“As a result, Mars became (the) extremely cold planet it is today,” said Dr. Fairén.

MarsFirstWater will search for any biomarkers like microbial lipids on Mars that may be evidence of life once they survive in this most habitable ancient site. Checking the chemical processes that took place in Martian rocks, for example, could tell us how much liquid water was present, allowing us to determine what kind of life might have survived there. The project will also search for biomarkers in the Martian geological record that are similar to those produced by microbes on Earth.

The team already has some initial results. They have discovered that some types of microbes found on Earth could prevent water on Mars from freezing in ice due to their biological processes, while some signs of ancient life could remain in wet clays below the Martian surface today that could be studied. by the rovers.

The next phase in the search for life on Mars will be to put all these clues together and use the data from the next missions to look for new signs of life. “We already know that Mars was habitable,” said Dr. Fairén. “The next question to answer is whether it was actually inhabited.”

Perseverance and ExoMars may not be enough; Instead, a life detection mission that can take samples from Mars directly for signs of life may be necessary to be sure. But there is little doubt that an answer to one of the best questions of our time is within reach.

“We know that the environmental conditions on early Mars were habitable,” said Dr. Schulze-Makuch. “There were lakes, oceans, it was raining. There could have been life.”

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