Today, however, Mars is a barren wasteland. Any water that it could ever have on its surface hundreds of millions of years ago is gone, while its atmosphere is a thin layer compared to how thick it could once have been. But could Mars have supported life in the past, and is there a possibility that some kind of life has survived today?
While we can’t answer these questions yet, we are closer than ever to finding out. And with new missions on the horizon, new clues begin to emerge.
Deserts
On Earth, life survives in a wide variety of places, from the deserts of the Sahara to the frozen glaciers of Antarctica. The surface of Mars currently has similarities to some of these places, so if we can find life in these areas of Earth, maybe we can find it on Mars as well.
Dr. Dirk Schulze-Makuch of the Technical University of Berlin, Germany, coordinated the Habitability of Martian Environments (HOME) project, which studied soil collected from the Atacama Desert in South America and examined which microbes were present. The results showed that life was fascinatingly tough.
” We show that even in the hyper-arid nucleus, there is still active microbial life ,” explained 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 Martian analogs, they could determine what kind of life might survive under the surface of Mars today.
“We were mainly interested in the Extremophiles (life that survives in extreme places on Earth),” said 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 he had a really high tolerance. “
While we can mimic conditions on Mars, we cannot replicate them exactly. The surface of Mars has much higher radiation levels 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 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 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 are greatly increased.
We have found evidence of ancient water on Mars in a wide variety of places. NASA’s Curiosity rover may have found an ancient lake bed, while the northern hemisphere of Mars may have contained a large ocean . Scientists want to take these studies even further.
Researcher Alberto Fairén, from the Spanish Astrobiology Center in Madrid, Spain, coordinates a project called MarsFirstWater . This project aims to calculate how much water there could have been on Mars in its first billion years, be it 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, such as NASA’s upcoming Perseverance rover, due to launch in July 2020, and Europa’s Rosalind Franklin rover, planned for launch in In 2022, the project aims to reconstruct and map the surface of ancient Mars like never before.
“Between 4.5 and 3.5 billion years ago, it is believed that Mars had an active surface hydrosphere that included glaciers, rivers, lakes, deltas and perhaps even a hemispheric ocean the size of the Mediterranean Sea,” Fairén said.
The emerging image of an early Mars suggests that its summers were similar to winters in Iceland and its winters resembled winters in Antarctica.
An earlier study by Dr. Fairén, called IcyMARS, concluded that ancient Mars may have been colder than previously thought, but still humid enough to be habitable. At some point in its history, water was stripped from the planet when its core cooled for unknown reasons, and its solar wind blew its atmosphere away.
“As a result, Mars became (into) the extremely cold planet that it is today,” says Fairén.
MarsFirstWater will look for any biomarkers such as microbial lipids on Mars that may represent evidence of life once they survive in this region. 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. The project will also look 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 into ice due to their biological processes, while some signs of ancient life could remain in moist clays below the current Martian surface that could be studied. by the rovers.
The next phase in the search for life on Mars will be to put together all these clues and use the data from upcoming missions to search for new signs of life. “We already know that Mars was habitable,” says Fairén. “The next question to answer is whether it was actually inhabited.”
Yes indeed; the Perseverance and ExoMars missions might not be enough. It would take a life detection mission that can sample Mars directly for signs of life to be sure. But there is little doubt that an answer to one of the best questions of our time is at our fingertips.
“We know that environmental conditions on early Mars were habitable,” said Dr. Schulze-Makuch. ‘There were lakes, oceans, it was raining. There could have been life. “
Original article
This article was originally published in Horizon, the EU Research and Innovation Magazine
