Water that once flowed across the surface of Mars was hot enough for alien life to survive, scientists have discovered. Asteroid impacts created craters surrounded by water-filled vents where temperatures reached between 50 C and 150 C, their new research shows. 

Heavily cratered martian highlands photographed by one of NASA’s Viking orbiters. Credit: NASA

Martian bugs could have thrived in such conditions. On Earth, microbes have been discovered living in similar waters, such as in the volcanic thermal springs at Yellowstone Park in the USA.

On Mars, which is covered with craters, the energy from the impacts was what heated the water in hydrothermal fractures, the scientists believe.

Researchers from the University of Leicester and the Open University, both in the UK, came to their conclusions after studying meteorites from Mars that fell to Earth.

One type, which has samples in London’s Natural History Museum, is called a nakhlite. They were found to have veins running through them that are filled with minerals which are produced by water.

By examining pieces of nakhlites under highly powerful microscopes, scientists at Leicester’s Department of Physics and Astronomy were able to discover more about the conditions under which the minerals formed.

Their results were then run through computers at the Open University in Milton Keynes to test what processes might have occurred on Mars. This showed them that in martian history the water was initially at a temperature of around 150 C and contained a lot of carbon dioxide from which carbonates formed. It then cooled to around 50 C forming the clays.

Planetary scientist Dr John Bridges, of Leicester, said: “Rovers on Mars – the Mars Exploration rovers Spirit and Opportunity, and the Mars Science Laboratory rover Curiosity – are studying rocks to find out about the geologic history of the Red Planet.

“While the orbiters and rovers are studying the minerals on Mars, we also have meteorites from Mars here on Earth. They come in three different groups, the shergottites, the nakhlites and the chassignites. Of most interest for the question of water on Mars are the nakhlites, because this group of Martian meteorites contains small veins, which are filled with minerals formed by the action of water near the surface of Mars.”

Dr Bridges added: “The mineralogical details we see tell us that there had been high carbon dioxide pressure in the veins to form the carbonates. Conditions then changed to less carbon dioxide in the fluid and clay minerals formed. We have a good understanding of the conditions minerals form in, but to get to the details, chemical models are needed.”

Dr Susanne Schwenzer, of the Open University’s Department of Physical Sciences, said: “Until John’s study was finished, I used the findings from orbiters around Mars, and modelled each of the new minerals individually. Before we had the detailed study of the nakhlite meteorites, we did not know that carbonates are forming first, followed by the clays. Therefore I was very excited to see the details of the new mineralogical study.”

She added: “The driving force heating the water might have been an impact into the Martian surface. And you only have to look at a map of Mars to see how numerous those are on the martian surface.”

Results from the research has been published this week in the journal Earth and Planetary Science Letters.