Between the lack of air and the constant bombardment of radiation and micrometeorites, humans will need some serious shelter before we can feel at home on the Moon or Mars. While inflating or 3D printing our houses could be one way to pack light for the long trip, the most efficient method might just be to move into the natural shelter that's already there. Now astronomers have systematically analyzed possible lava tubes on the Moon and Mars, and found they may be just what Red Planet realtors are looking for.
Living underground is the easiest way to escape the harsh conditions of the lunar or Martian surface, and scientists have already found a few candidates. NASA has found hundreds of deep pits in the pock-marked rock of the Moon that could make good hidey-holes from the elements, and there's evidence of sprawling networks of lava tubes below the surface.
It's the latter that caught the eye of researchers from the Universities of Padova and Bologna. Here on Earth, lava flows can leave behind tunnels in solid rock after the molten-hot fluid drains, creating what are known as lava tubes, and the team wanted to find the best candidates for these tunnels on the Moon and Mars.
To do so, the scientists studied high-resolution Digital Terrain Models, put together from data gathered by spacecraft, and compared these lava tubes on Earth, Mars and the Moon to see how viable they may be as shelter. And the results confirmed previous research that suggested they may be big enough to build cities inside, thanks to the lessened stresses of gravity keeping them up.
"The comparison of terrestrial, lunar and Martian examples shows that, as you might expect, gravity has a big effect on the size of lava tubes," says Riccardo Pozzobon, a researcher on the study. "On Earth, they can be up to 30 m (98 ft) across. In the lower gravity environment of Mars, we see evidence for lava tubes that are 250 m (820 ft) in width. On the Moon, these tunnels could be 1 km (0.6 mi) or more across and many hundreds of kilometers in length.
"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 flux, potentially providing safe habitats for future human missions. They are also, potentially, large enough for quite significant human settlements."
The problem is, it's tricky to find these lava tubes under all that rock. To get around that, researchers from the University of Trento have presented the concept for a spacecraft that could detect the caverns from orbit. The system would use radar to map out the size and shape of lava tubes, as well as determine their composition. That information could then inform suitable sites for eventual human colonies.
"The studies we have developed show that a multi-frequency sounding system is the best option for detecting lava tubes of very different dimensions," says Leonardo Carrer, lead researcher on the Trento study. "The electromagnetic simulations show that lava tubes have unique electromagnetic signatures, which can be detected from orbit irrespective of their orientation to the radar movement direction. Therefore, a mission carrying this instrument would enable a crucial step towards finding safe habitats on the Moon for human colonization."
Both studies were presented at the European Planetary Science Congress in Riga, Latvia, last week.