A team of NASA scientists has suggested that Mars rovers may need to dig deeper than first thought to give them the best chance of finding evidence of ancient microbial life on the distant planet.
The team’s recent research found that cosmic rays from the sun break down small molecules such as amino acids — the basic building blocks of life — much faster than expected. The existence of certain amino acids is key in scientists’ quest to prove that microbial life once existed on Mars.
“Our results suggest that amino acids are being destroyed by cosmic rays in the surface rocks and regolith of Mars 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 2 inches (about 5 centimeters). At those depths, it would take only 20 million years to completely destroy amino acids.”
As scientists look for evidence of life on Mars from billions of years ago, when the planet was more Earth-like, the material collected at these shallow depths may not be as useful as first thought. Earth’s thick atmosphere and global magnetic field protect the planet from most cosmic rays, but Mars lost this protection billions of years ago. Back when it had a thicker atmosphere, the red planet contained liquid water. “Since liquid water is essential for life, scientists want to know if life originated on Mars and look for evidence of ancient life on Mars by examining Martian rocks for organic molecules such as amino acids,” NASA said.
The scientists’ findings suggest that samples of Martian rock should be extracted from a depth of about 2 meters, where such evidence should remain intact.
Since NASA’s Perseverance rover can only drill a few inches, the development could prompt the team behind the current Mars mission to adopt a new strategy for the rover, which is collecting rock monsters on the red planet for the last 10 months.
A solution proposed by the scientists involves extracting samples from exposed outcrops such as microcraters that are less than 10 million years old, or from the material ejected from impacts involving these craters.
The space agency also points out that although amino acids have not yet been found on Mars, they are in meteorites, including one from the red planet. “We identified several straight-chain amino acids in the Astrobiology Analytical Lab at Goddard in the Antarctic Mars meteorite RBT 04262 that we believe to have originated on Mars (no contamination from terrestrial biology), although the mechanism of formation of these amino acids in RBT 04262 remains unclear,” said Danny Glavin of NASA Goddard, who was also involved in the recent study. “Because Martian meteorites are typically ejected from depths of at least 3.3 feet (a meter) or more, it is it is possible that the amino acids in RBT 04262 were protected from cosmic rays.”
NASA’s Jet Propulsion Laboratory, which oversees the current Mars mission, has yet to comment on the findings. Perseverance has already collected some samples for later return to Earth so scientists can analyze the material in advanced labs. However, the team can now redirect the rover to the kind of locations mentioned in the scientists’ study.