Dig deep to find the Martians

Space probes to Mars need to dig deep if they are to find alien life, UK experts said today. Any Martian microbes are hiding several feet down to escape deadly radiation from space and the Sun, their report reveals.

The picture is a Nasa artist’s impression of a future deep-drilling lander. Image credit: NASA

Many scientists believe that living cells exist on the Red Planet, possibly in a form of suspended animation. Drills on current Mars missions can find signs suggesting that there was once life on Mars, but any alien remains they find will be dead.

Scientists at University College London say this is because microbes could not survive the radiation levels for long enough any closer to the surface of Mars than a few metres deep. That is beyond the reach of even state-of-the-art drills.

Unlike Earth, Mars does not have a magnetic field, thick atmosphere or oceans of water to shield the planet against deadly radiation levels. The UCL scientists’ study, published in the journal Geophysical Research Letters, maps out the cosmic radiation levels at various depths on Mars.

It takes into account different surface conditions on Mars and shows that the best place to look for living cells is within the ice at Elysium, a newly discovered frozen sea near the Martian equator.

Lead author of the UCL study, Lewis Dartnell, 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.”

He added: “It just isn’t 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.

The team found that the best places to look for living cells on Mars would be within the ice at Elysium because the frozen sea is relatively recent. It is believed to have surfaced in the last five million years and so has been exposed to radiation for a relatively short amount of time. Ice is also relatively easy to drill into.

Other ideal sites include recent craters, because their surface material has been exposed to less radiation, and the gullies recently discovered in the sides of craters which are thought to have flowed with water in the last five years. The UCL team carried out tests to study the effects of radiation on different types of surface – dry rock, water ice and rock with layers of permafrost.

Related: Martian life may be hidden in tunnels that could home humans too

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