Probes designed to find life on Mars do not drill deep enough to find the living cells that scientists believe may exist well below the surface of Mars, according to research led by UCL (University College London). Although current drills may find essential tell-tale signs that life once existed on Mars, cellular life could not survive the radiation levels for long enough any closer to the surface of Mars than a few metres deep beyond the reach of even state-of-the-art drills.
The study, published in the journal Geophysical Research Letters (GRL), maps out the cosmic radiation levels at various depths, taking into account different surface conditions on Mars, and shows that the best place to look for living cells is within the ice at Elysium, the location of the newly discovered frozen sea on Mars.
The lead author, Lewis Dartnell, UCL Centre for Mathematics and Physics in the Life Sciences & Experimental Biology (CoMPLEX), said: "Finding hints that life once existed proteins, DNA fragments or fossils would be a major discovery in itself, but the Holy Grail for astrobiologists is finding a living cell that we can warm up, feed nutrients and reawaken for studying.
"It just isnt plausible that dormant life is still surviving in the near-subsurface of Mars within the first couple of metres below the surface in the face of the ionizing radiation field. Finding life on Mars depends on liquid water surfacing on Mars, but the last time liquid water was widespread on Mars was billions of years ago. Even the hardiest cells we know of could not possibly survive the cosmic radiation levels near the surface of Mars for that long."
Survival times near the surface reach only a few million years. This means that the chance of finding life with the current probes is slim. Scientists will need to dig deeper and target very specific, hard-to-reach areas such as recent craters or areas where water has recently surfaced.