Mars is a pretty hostile place for visitors. Having lost its magnetic field and most of its atmosphere, the Red Planet’s surface is exposed to high levels of cosmic radiation, which we are shielded from by Earth’s magnetosphere. In large doses, the highly ionizing rays can penetrate tissue leading to radiation sickness or even death. Therefore, when the first astronauts land on Mars there needs to be adequate shelter to protect them from the planet’s inhospitable conditions.
Scientists have discovered that the habitats that could offer this protection are underground lava tubes. Found on terrestrial planets, as well as moons, lava tubes are formed when channels of lava cool and harden to form igneous rock. When the lava flow beneath ultimately stops and drains out, a natural subsurface cave is left behind. Whilst on Earth these tubes reach only about 30 meters (100 feet across), on Mars, where there is less gravity, they can be up to 250 meters (820 feet) in width.
A new study, published on the preprint server arXiv, has identified three candidate lava tubes that could serve as home sweet home for future visitors, as well as a possible site for discovering previous microbial life on Mars. Located in the large Hellas impact basin in Mars’ southern hemisphere, the lava tubes sit in close vicinity of the ancient volcanic mountain Hadriacus Mons.
Radiation at this lower-lying region of Mars has already measured at levels considerably less than the rest of the planet’s surface. To add to the allure of these caverns, experiments by the study authors in lava tubes on Earth suggest that they could shield a further 82 percent of incoming radiation. Whilst this exposure would still be significantly more than on Earth, a reduction of any kind would be welcomed by crewed missions.
Lava tubes have previously been suggested by scientists as possible habitats on the Moon, where these lunar caverns are vast enough to fit the historic city center of Riga inside. But to find these underground nooks on Mars, Professor Antonio Paris and colleagues had to scour images from cameras onboard NASA’s Mars Reconnaissance Orbiter (MRO) for clues. These come in the form of pit crater chains – a series of round depressions caused by the collapsing or sinking of a surface above a hollow void.
Another giveaway of lava tubes are “skylights”– the open entrances to these caves. On Earth, astronauts use skylights to access lava tubes for training, but on Mars, the authors suggest that these openings could even be sealed off, to enable the caverns to be warmed up and pressurized with breathable air.
Regardless, “these natural caverns would provide the crew protection from excessive radiation exposure, shelter them from the bombardment of micrometeorites… and provide them a degree of protection from extreme temperature fluctuations,” the authors wrote in their paper, accepted for publication by the Journal of the Washington Academy of Sciences.
Although lava tubes are a rather unusual place to call home, they could well be the most comfortable place to be on the Red Planet.