A new NASA experiment suggests the search for life on Mars may require digging deeper following the discovery that cosmic rays likely quickly destroy amino acids that would be found on the red planet’s surface.
The discovery of amino acids on Mars would be a significant step in the search for Martian life, as they are a key component to building proteins in terrestrial life.
“Our results suggest that amino acids are destroyed by cosmic rays in the Martian surface rocks and regolith at much faster rates 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 (around five centimeters). At those depths, it would take only 20 million years to destroy amino acids completely. The addition of perchlorates and water increases the rate of amino acid destruction even further,” he added.
The research also demonstrated that current drilling by rovers on Mars would be unlikely to discover any signs of ancient life at their current depths.
“Missions with shallow drill sampling have to seek recently exposed outcrops – e.g., recent microcraters with ages less than 10 million years or the material ejected from such craters,” Pavlov observed.
Unlike on Earth, where the thick atmosphere and magnetic field shield against most cosmic rays, Mars has no such current protections (though some have suggested it did in the past). The growing evidence of water on Mars, however, has also led to new efforts to discover other evidence from amino acids in the planet’s rocks.
In the NASA experiment, the research team created test tubes sealed in conditions seeking to mirror those of the surface of Mars. The samples were also blasted with gamma radiation to simulate conditions on the red planet.
“Our work is the first comprehensive study where the destruction (radiolysis) of a broad range of amino acids was studied under a variety of Mars-relevant factors (temperature, water content, perchlorate abundance) and the rates of radiolysis were compared,” said Pavlov. “It turns out that the addition of silicates and particularly silicates with perchlorates greatly increases the destruction rates of amino acids.”
Amino acids have not yet been discovered on Mars. Researchers remain hopeful, however, as such materials have been found in some meteorites, including at least one from Mars.
In 2009, researchers at NASA’s Goddard Space Flight Center reported “the discovery of an excess of the left-handed form of the amino acid isovaline in samples of meteorites that came from carbon-rich asteroids.” The finding has led to some speculation that life even began in space.
The discovery did show that meteoroids carry similar amino acids to those found on Earth. The researchers also noted that organic matter has been observed on Mars by both the Curiosity and Perseverance rovers, but the signs could have also been created by non-biological forces.