When Earth was still a young and temperamental planet, it had frequent volcanic outbursts. So did the Moon — and Mars.
What all those massive eruptions left behind are underground lava tubes. When the upper layers of ancient lava flows started to cool and harden, there would still be rivers of lava bubbling underneath. It eventually melted or drained into the rocks below and left behind enormous tunnels that could have been havens for life which was otherwise unable to survive in the sunlight. Billions of years later, scientists are eyeing these remnants of subsurface magma flows for exploration (which could answer the persistent question of whether there was ever life on Mars) and even as potential astronaut habitats.
“Besides providing a window into geological history, lava tubes offer environmental conditions that are relatively stable and likely to be more hospitable than those found on a planet’s surface,” said geologist Sid Perkins in a study recently published in PNAS. “If Mars ever hosted life, it may have moved into such refugia as the planet evolved and surface conditions became increasingly harsh.”
Early Mars is thought to have had an environment similar to that of early Earth. It actually had an atmosphere, and is also thought to have had liquid water, both conditions that would have been hospitable to life as we know it. Could aliens have been crawling in there? Since Mars got radiation-blasted into a frozen desert, some scientists believe that hypothetical ancient life-forms may have retreated to the lava tubes for a last chance at staying alive. The chance that Martian life may have escaped to lava tubes and may even still exist.
Potential life and astronaut shelter is why NASA geologist Laura Kerber came up with the ingenious concept for the Moon Diver. A lunar lander would take this cave-diving robot to its destination, where the robot would be lowered into a skylight (above) on the surface of a lava tube and use its suite of instruments and sensors to probe around and explore as far as its 984-foot tether (also a lifeline for power and communications) would allow. Some of its hypersensitive instruments meant to analyze it geologically and search for life would include three hi-res cameras, a spectrometer to look into the chemistry of minerals.
The Moon Diver’s microscope would be capable of imaging things—such as organic chemicals or biofilms formed by living or fossilized microbes—at different wavelengths that would make them impossible to see with the naked eye. Suddenly, the concept of ancient aliens is not so farfetched.
“Exploring lava tubes on the moon and Mars might yield information not only about those bodies and their impact histories but also about the Earth and the Sun,” Perkins said.
The problem for the Moon Diver is that it would have to get everything done between the lunar sunrise and sunset. After the sun goes down on the Moon, its equipment would be at risk of damage from the blistering cold and possibly unable to restart. Nights on Mars can get as freezing as -100 degrees Fahrenheit at night around its equator, still nothing compared to the -280 degrees of a lunar night.
Lunar lava tubes have been considered for human habitation before. Martian tubes have the same potential. It sounds convenient, but could be dangerous, which is why robots like the Moon Diver are needed to find out how safe they are in addition to searching for fossilized aliens or signs of geological phenomena. The top layers that first cooled when lava flowed underneath can be up to a hundred feet deep, but that still doesn’t make it impossible for them to cave in. Moonquakes and Marsquakes happen. The interior itself could be a hazardous zone full of regolith.
If we really are going to shoot for the moon in less than four years, and possibly send humans to Mars within the next decade or so, exploring lava tubes could reveal anything from built-in habitats to signs of extraterrestrial life. NASA better send cave-diving bots out there soon.