Mars spacecraft may have to dig deeper than thought to find traces of life
Mars rovers may have to dig deeper to find signs of ancient life. New research shows that certain proteinbuilding amino acids that could be evidence of ancient life on Mars are more susceptible to radiation than scientists thought, meaning any amino acids left by life-forms might have only survived if they were buried deep beneath the planet’s surface. “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,” Alexander Pavlov, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said. “Current Mars rover missions drill down to about two inches (around five centimetres). At those depths, it would take only 20 million years to destroy amino acids completely.”
While 20 million years might seem like an incredibly long time, this is a brief period in the development of planets and life. That’s especially true when you consider that the signs of life that rovers such as Curiosity are searching for on Mars would have been present billions of years ago. The team discovered that the presence of liquid water, which was abundant on Mars billions of years ago, and perchlorate (charged ions of a chlorine atom surrounded by four oxygen atoms) could have sped up the destruction of amino acids.
To address the problem, searches could shift their focus to locations where geological processes have brought buried rock to the surface. “Missions with shallow drill sampling have to seek recently exposed outcrops – for example, recent microcraters with ages less than 10 million years or the material ejected from such craters,” Pavlov said. “Our work is the first comprehensive study where the destruction 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,” Pavlov said.