According to a new NASA lab experiment, rovers may have to dig about two meters or more below the surface of Mars to find signs of ancient life, because ionizing radiation from space breaks down small molecules such as amino acids relatively quickly.
Amino acids can be made by life and by non-biological chemistry. However, finding certain amino acids on Mars would be considered a potential sign of ancient life on Mars, as they are widely used by terrestrial life as a component to build proteins. Proteins are essential for life because they are used to make enzymes that speed up or regulate chemical reactions and to make structures.
“Our results suggest that cosmic rays in the surface rocks and regolith of Mars are destroying amino acids much faster than previously thought,” said Alexander Pavlov of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Current Mars rover missions drill down to about two inches (about five centimeters). At those depths, it would take only 20 million years to completely destroy amino acids. The addition of perchlorates and water increases the rate of amino acid destruction even further.” 20 million years is a relatively short time, as scientists look for evidence of ancient surface life that would have been present billions of years ago when Mars was more like Earth.
This result suggests a new search strategy for missions limited to sampling at shallow depths. “Missions with shallow cores should look for recently exposed outcrops — for example, recent micro-craters less than 10 million years old or the material ejected from such craters,” said Pavlov, lead author of a study. paper about this research published June 24 in Astrobiology.
cosmic rays are high-energy particles (usually protons and helium ions) generated by powerful events on the sun and in deep space, such as solar flares and exploding stars† They can break down or destroy organic molecules when they penetrate meters (meters) into a solid rock, ionizing and destroy everything in their path.
Earth’s thick atmosphere and global magnetic field shield its surface from most cosmic rays. In his youth, Mars also had these characteristics, but lost this protection as he got older. However, there is evidence that billions of years ago, the thicker atmosphere allowed liquid water to persist on the surface of the Red Planet. Because liquid water is essential for life, scientists want to know if life originated on Mars, and are looking for evidence of ancient life on Mars by examining Martian rocks for organic molecules such as amino acids.
The team mixed different types of amino acids in silica, hydrated silica or silica and perchlorate to simulate the conditions in Martian soil and sealed the samples in test tubes under vacuum conditions to simulate the thin Martian air. Some samples were kept at room temperature, about the warmest ever on the surface of Mars, while others were cooled to a more typical minus 67 degrees Fahrenheit (minus 55 degrees Celsius). The monsters are blasted with different levels of gamma rays – a type of highly energetic light – to simulate doses of cosmic rays to those received from about 80 million years of exposure to the surface rocks of Mars.
The experiment is the first to mix amino acids with simulated Martian soil. Previous experiments tested gamma rays on pure amino acid samples, but it is highly unlikely that a large cluster of a single amino acid will be found in a billion-year-old rock.
“Our work is the first comprehensive study examining the destruction (radiolysis) of a wide range of amino acids under a variety of Mars-relevant factors (temperature, water content, perchlorate abundance) and comparing the rates of radiolysis,” Pavlov said. . “It turns out that the addition of silicates and especially silicates with perchlorates greatly increases the destruction rate of amino acids.”
Although no amino acids have been found on Mars yet, they are discovered in meteorites, including one from Mars. “We identified several straight-chain amino acids in the Astrobiology Analytical Lab in Goddard in the Antarctic Mars meteorite RBT 04262 that we believe to be from Mars (no contamination by terrestrial biology), although the mechanism of formation of these amino acids in RBT 04262 remains unclear,” said Danny Glavin, a co-author of the paper at NASA Goddard. “Since Mars meteorites are typically ejected from depths of at least 3.3 feet (one meter) or more, it’s possible that the amino acids in RBT 04262 were shielded from cosmic rays.”
Organic Matter Found on Mars by NASA’s Curiosity and Perseverance vagabonds; however, it is not a conclusive sign of life, as it may have originated from non-biological chemistry. The results of the experiment also imply that it is likely that the organic material observed by these rovers has been altered by radiation over time and therefore not as it was when it was formed.
The research was funded by NASA under grant number 80GSFC21M0002, 15-EXO15_2-0179 and NASA’s Planetary Science Division Internal Scientist Funding Program through the Fundamental Laboratory Research (FLaRe) work package.
Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of any press releases posted on EurekAlert! by sponsoring institutions or for the use of information through the EurekAlert system.
#NASA #experiment #suggests #dig #deep #evidence #life #Mars