Some scientists believe that if we want to find life on Mars we should dig deep below the planet's surface and beyond the reach of any currently planned missions. The reason for this is because within the first several yards of the planet's surface, there are too many lethal doses of cosmic radiation:
Unlike Earth, Mars is no longer protected by a global magnetic field or thick atmosphere. As a result, the planet has been vulnerable to radiation from space for billions of years.
“Even the hardiest cells we know of could not possibly survive the cosmic radiation near the surface of Mars for that long,” said study leader Lewis Dartnell of University College London.
Dartnell and his team developed a radiation dose model that calculates how much solar and galactic radiation Mars is subjected to. They tested three surface soil scenarios and calculated particle energies and radiation doses on the surface and at various depths underground. From this, they calculated the length of time that the hardiest known cells on Earth could survive.
The team believes a good place to look for living cells on the red planet is in ice from a frozen sea recently discovered on Elysium Plantia, a major volcanic region on Mars. Scientists think the sea formed only within the last five million years.