The Mars spacecraft may have to dig deeper than expected to find traces of life

Mars explorers may have to dig deeper for signs of ancient life.

New research shows that certain protein-building amino acids that could be evidence of ancient life on Earth Mars more susceptible to radiation than scientists thought, meaning any amino acids left behind by life forms might only survive if they were buried deep beneath the planet’s surface.

“Our results show that amino acids are destroyed by cosmic rays in Martian surface rock and regolith at a much faster rate than previously thought,” Alexander Pavlov, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement. statement. “Current Mars rover missions are drilling to about two inches (about five centimeters). At that depth, it would take only 20 million years to completely destroy the amino acids.”

Related: Possible sign of Martian life? Curiosity rover finds ‘tantalizing’ Red Planet organics

While 20 million years may seem like a very long time, it is a brief period in the development of the planet and life. That’s especially true when you consider that roaming signs of life like curiosity was looking at Mars would have been present billions of years ago, when Mars was more like Earth.

The team found that the presence of liquid water, which was abundant on Mars billions of years ago, and perchlorate (a charged ion of a chlorine atom surrounded by four oxygen atoms) can accelerate the breakdown of amino acids. The findings were conveyed by the first experiment to mix amino acids with simulated Martian soil.

Research shows that we don’t dig deep enough beneath the Martian surface to find signs of life. To address this problem, searches could shift their focus to locations where geological processes have brought buried rock to the surface.

“Missions with shallow drill sampling should look for recently exposed outcrops – for example, recent micro-craters less than 10 million years old or material ejected from such craters,” Pavlov said.

How Mars lost its magnetosphere

One of the main reasons Earth is more hospitable to life than Mars is because of its strong magnetic field, magnetospherearound our planet.

Magnetosphere protects earth’s atmosphere from solar wind (charged particles from the sun) and other stellar fragments ( cosmic rays) by causing them to travel down magnetic field lines and out behind Earth, similar to how a boat creates an arc shock as it moves through water.

These charged particles can degrade or destroy organic molecules as they penetrate the meter of solid rock, ionizing and destroying everything in their path. radiation from sun can also stripping the planet’s atmosphere a key factor in its ability to retain liquid water.

Billions of years ago, Mars lost its magnetic field, atmosphere and, finally, much of the liquid water that sustains life. It means looking for lifeon Mars involves looking for signs of ancient biological activity in Martian rocks through indicators such as amino acids.

To test how effective our current search is, the team of scientists mixed different types of amino acids in silica, hydrated silica, or silica and perchlorate to simulate conditions on Martian soil, and then sealed the samples in test tubes under vacuum to simulate thin Martian air.

While some of these samples were kept at the same temperatures as those on the Martian surface, others were cooled to minus 67 degrees Fahrenheit (minus 55 degrees Celsius). All samples were exposed to highly energetic gamma rays to simulate the cosmic ray exposure that rocks on the Martian surface would have experienced about 80 million years ago.

“Our work is the first comprehensive study in which the destruction (radiolysis) of various amino acids was studied under various Mars-relevant factors (temperature, moisture content, perchlorate abundance) and radiolysis rates were compared,” Pavlov said. “It turned out that the addition of silicates, and in particular silicates with perchlorates, greatly increased the rate of amino acid breakdown.”

Researchers haven’t found amino acids on Mars yet, but they have found these molecules on meteorite, including one from the Red Planet. But how do these complex chemicals form in Meteorite Mars RBT 04262 discovered in Antarctica in 2004, remains unclear.

Since meteorites are typically ejected from at least 3.3 feet (1 meter) below the Martian surface, the new research implies that the amino acids in RBT 04262 may have been shielded from harsh solar radiation and cosmic rays.

The results also show that complex organic molecules that Mars crossed Curiosity and Perseverancehas been discovered, which intrigues scientists but is not an indicator of life, may have been altered over time by radiation exposure.

The team’s research was published June 26 in the journalAstrobiology.

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