Most of Mars is extremely inhospitable to life, but there may be an alternative solution. Areas near cave entrances should, in theory, be protected from some of the harmful radiation that bombards the planet’s surface.
As Mars does not have a global magnetic field or dense atmosphere like Earth, its surface is exposed to dangerous ultraviolet (UV) and ionizing space radiation, which would pose a problem for native life and human explorers alike. Anything alive on the Martian surface would be exposed to radiation doses that are 900 times greater, on average, than it would experience on Earth.
However, images of the planet taken from orbit have shown what appear to be cave entrances, and the interior of these caves can be shielded from these harmful rays. Daniel Viúdez-Moreiras, from the National Institute of Aerospace Technology in Spain, now calculated how much ultraviolet radiation would still reach different types of caves at various locations on Mars.
He found that, in many cases, ultraviolet radiation levels inside caves would be about 2 percent of surface levels. These radiation levels are low enough to be relatively safe, yet high enough to support organisms that need light to produce energy through photosynthesis.
It is not clear whether ionizing radiation – potentially even more dangerous than UV – would be blocked in the same way, but it is likely, according to Viúdez-Moreiras. “Ionizing radiation doesn’t exactly behave like UV radiation,” he says. “However, ionizing radiation is also expected to be strongly attenuated in pit craters and cave skylights.”
The consequences of this are twofold: caves can be safe places for human explorers to hide from the extreme conditions of the Martian surface, and they can also be some of the best places to look for signs of life on the Red Planet. No lander or rover has ever visited a cave on Mars, but doing so would be the best way to find out if they are actually habitable, says Viúdez-Moreiras.