Martian life could have survived in underground tunnels, say space scientists. And the same features could provide ready-made habitats for human colonies.
The pioneering settlers would take advantage of vast subterranean caves called lava tubes, created by ancient volcanic activity on the red planet. They are believed to exist on the Moon as well.
The caverns – big enough to house streets or towns – have already been found on Earth, in locations including California, Hawaii, Australia and Lanzarote.
Italian researchers say that orbiting spacecraft will be able to use radar to locate similar structures on the Moon. As lunar bases, they would shield astronauts against deadly cosmic radiation and impacts by micro-meteorites, because the Moon has no protective atmosphere.
On Mars, similar lava tubes might have protected simple microbial life which would have been unable to thrive at the surface due to the dangerous levels of radiation. Mars has no magnetic field to deflect such radiation, unlike the Earth.
European Space Agency astronauts have already begun training in lava tubes on Lanzarote in the Canary Islands.
The latest proposals were made at the annual European Planetary Science Congress in Riga, Latvia.
Lava tubes can be formed when a flow of molten rock close to the surface develops a hard crust which then thickens to form a roof.
Alternatively, lava flowing between layers of rock can leave behind a network of empty caverns and tunnels.
Scientists from the universities of Padua and Bologna studied high-resolution data from orbiting spacecraft to compare lava tube candidates on the Moon and Mars with those on Earth.
Dr Riccardo Pozzobon, of the University of Padua, said: “Gravity has a big effect on the size of lava tubes. On Earth, they can be up to 30 metres across. In the lower gravity environment of Mars, we see evidence for lava tubes that are 250 metres in width.
“On the Moon, these tunnels could be a kilometre or more across and many hundreds of kilometres in length.”
He added: “These results have important implications for habitability and human exploration of the Moon but also for the search of extraterrestrial life on Mars.
“Lava tubes are environments shielded from cosmic radiation and protected from micrometeorites, potentially providing safe habitats for future human missions.
“They are also, potentially, large enough for quite significant human settlements.”
Skymania asked Dr Pozzobon whether he thought the lava tubes on Mars might have protected Martian microbes.
He told us: “That’s exactly the idea. The local environmental conditions within a lava tube void, shielded from cosmic radiation that sterilizes basically the whole surface of Mars up to tens of centimeters in the soil, could have provided favourable conditions for microbial life sustainability (present or past we do not know).
“Atmospheric conditions can be locally different as well, as happens in terrestrial caves. It’s a whole new topic, and we’re just scratching the surface.
“With ExoMars rover that is hopefully going to be launched in the near future, we’ll be able to drill and penetrate the ground at more than one metre (where UV and cosmic radiation have no more effect), and analyze the presence of organic compounds that could have survived at depth. And this type of discovery may be extended as well in such a well protected environment as lava tubes offer.”
Related: Dig deep to find the Martians
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