Possible signs of life discovered on Mars: what attracted the attention of scientists

NASA scientists have discovered a gas on Mars that is produced by living things on Earth. This made researchers wonder what might be hiding on the Red Planet.

A constant flow of methane from Gale Crater was found by the Curiosity rover. The gas appears at different times of the day, and its level fluctuates depending on the season, sometimes 40 times higher than standard indicators, the Daily Mail writes.

Although NASA has not yet found life on Mars, scientists believe that the source of methane is deep underground. The team suggests that the gas may be trapped under hardened salt and only seep out when the temperature on Mars rises - or when Curiosity drives over the crust and cracks it.

On Earth, this simple molecule, composed of one carbon atom and four hydrogen atoms, is usually a sign of life: it is a gas released by animals when they digest food.

Curiosity has been roaming the surface of Mars since 2012. Scientists say that the constant flow of methane from the crater is the most amazing thing that NASA's rover has seen since then. This is the only place on the planet where Curiosity has detected the gas. But no one has noticed cows or people on Mars who have just eaten a large portion of cabbage, the publication reminds.

In laboratory experiments that simulate the conditions of the Martian soil, scientists have modeled the following possible situation.

For a long time, salts, a substance known as "regolith," have been released from beneath the rocky, dusty surface of the planet. These salts are called perchlorates, and they are abundant on Mars.

Perchlorates, which are toxic, are found in the ice beneath the planet's surface. If there is too little atmosphere, this ice gradually evaporates. And when this salty vapor filters through the regolith, it leaves a piece of itself behind.

When enough of these salts accumulate in the regolith, they form a kind of shell - like dried sand that has turned into a brittle crust or a piece of coffee grounds after drinking espresso.

"On Mars, such a process can occur naturally over a long period of time in shallow permafrost regions, and it is possible that enough salt can accumulate in the upper layer to form a seal," the scientists write in a new study published in the journal JGR Planets.

As the salt steam rises, methane also appears. Its source is still a mystery. It may come from some living creatures or from geological processes beneath the planet's surface that are still invisible to scientists.

Wherever it comes from, it is trapped under this salt crust.

By pumping different concentrations of perchlorate through a simulated Mars regolith, scientists found that it takes three to 13 days to form this impenetrable crust. A 5 or 10 percent concentration of perchlorate was also required to create a solid salt crust.

Scientists injected neon gas under the crust as a substitute for methane, confirming that the layer was strong enough to hold the gas underneath. But then, when the planet's temperature rises at certain times of the day or in certain seasons, this crust breaks, releasing methane outward. And that's when the methane can end up in the air.

However, it's not just temperature that can cause crustal cracking.

The crust is probably about two centimeters thick. And Curiosity is heavy enough to penetrate it, the scientific community writes.

"To test this hypothesis, it would be useful to measure methane when the rover has just arrived at a site with a large number of high-salt elements (e.g., salt veins). Another test would be to try to breathe in Martian air while drilling into a salt-rich surface," they say.

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