NASA experiment suggests need to dig deep for evidence of life on Mars
rovers may have to dig about 6.6 feet (two meters) or more under the Martian surface to find signs of ancient life
finding certain amino acids on Mars would be considered a potential sign of ancient Martian life
"Our results suggest that amino acids are destroyed by cosmic rays in the Martian surface rocks
A period of 20 million years is a relatively brief amount of time because scientists are looking for evidence of ancient life on the surface
Cosmic rays are high-energy particles (mostly protons and helium ions) generated by powerful events on the sun and in deep space,
Earth's thick atmosphere and global magnetic field shields the surface from most cosmic rays.
The team mixed several types of amino acids in silica, hydrated silica, or silica and perchlorate to simulate conditions in Martian soil