Clues to life on Mars from the Atacama Desert

The idea that there might once have been living organisms on Mars is a fascinating one, and even more so is the notion that some form of very primitive life might still be there. However, clues as to where the evidence for past or present life could be found are coming from a very strange direction, namely studies of the Atacama Desert in Chile, South America.

The Atacama Desert is one of the driest places on Earth and thus offers a reasonably close parallel to conditions on Mars – or at least to Mars as it might have been in fairly recent geological time.

The point is that microbes – very simple life forms – can survive for many years in water-free environments and reactivate when water again becomes available. This has been shown to happen in the Atacama Desert, where microbes survive in a dormant state in salt crusts (see picture) that absorb any water that happens to be around. This need not even be liquid water, because salt can take water directly from the air.

The question is therefore whether similar conditions could exist on Mars, given that it is known that there was once abundant liquid water on the planet that could have given rise to salt deposits as it evaporated. Indeed, such deposits have been discovered in Mars’s southern uplands. Modern Mars is not totally devoid of water, although most of it exists as ice at the north polar cap and beneath the surface. There are also very small amounts of water vapour in the thin atmosphere of the planet.

Given the much drier conditions on Mars, it is conceivable that evolutionary processes might have worked differently than on Earth, such that lifeforms could have survived on Mars that would not have done so on Earth. It is therefore going to be very interesting for future rover missions to explore the salt deposits on Mars to see if primitive life has survived. If it can do so in the Atacama, there is a reasonable chance that this is also possible in comparable environments on Mars.

© John Welford