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Starts With A Bang

Yes, The First Humans On Mars Should Consider Becoming Cave-Dwellers

The interior of Lava River Cave, shown here, has intact wall linings that showcase the basalt interior of the lava tubes. While a “flat floor” may be rare inside lava tubes, both on Earth and Mars, and Martian lava tubes are likely much larger, the interior features should otherwise look much the same. (DAVE BUNNELL / THE VIRTUAL CAVE)

If you think life on Earth is hard, wait until you see Mars.

If you think life on Earth is hard, try living on Mars.

Mars, as photographed from the surface (L) and from space (R). The Martian surface has many unattractive features for humans, including frequent dust storms, large amounts of radiation, enormous temperature swings, and frequent micrometeorite impacts. (NASA/JPL-CALTECH/CORNELL/ASU (L); NASA (R))

With at atmosphere only 0.7% as thick as Earth’s, pure, liquid water is impossible on the Martian surface.

Seasonal frozen lakes appear throughout Mars, showing evidence of (not liquid) surface water. These are just a few of the many lines of evidence that point to a watery past on Mars, but that support the idea that pure liquid water, without any impurities in it, cannot persist on the Martian surface due to the low atmospheric pressure. (ESA/DLR/FU BERLIN (G. NEUKUM))

With no active magnetic field, cosmic and solar radiation would be lethal to unshielded surface-dwelling humans.

Mars, the red planet, has no magnetic field to protect it from the solar wind, meaning that it loses its atmosphere in a way that Earth doesn’t. Additionally, solar and cosmic radiation makes it to the Martian surface whereas Earth’s field deflects it away, posing a deadly, cancerous risk to any Martian surface-dwellers. (NASA / GSFC)

Additionally, temperatures swing by some 170 °F (93 °C) from day-to-night, presenting severe habitability challenges.

During Martian summers, dust storms frequently occur, which can effectively blot out the Sun for weeks at a time to an observer on the Martian surface. If you don’t want to get pieces of Mars’s regiolith everywhere, you’ll need some way to shelter yourself and your equipment from these frequent events. Mars can be seen before (L) and after (R) a dust storm. (NASA/JPL/MALIN SPACE SCIENCE SYSTEMS, FROM MARS GLOBAL SURVEYOR)

Finally, dust storms abound while small micrometeorites frequently impact Mars, posing threats to surface-dwellers.

Shown in the same colors that human eyes would see it, this iron-nickel meteorite represents the first time that humanity ever discovered such a meteorite on the surface of Mars, from NASA’s Opportunity rover. Mars is littered with craters large and small, and has its surface impacted by meteorites more frequently than Earth. (NASA / JPL / CORNELL)

Fortunately, there’s a subterranean solution to many of these problems: lava tubes.

Lava tubes, found on Earth, the Moon, and Mars, but expected to be on many planets, provide underground shelter from harsh surface conditions. With the appropriate infrastructure, the first Martian settlements might benefit from using such a location instead of surface-dwelling. (DAVE BUNNELL / UNDER EARTH IMAGES)

In a new study, researchers conclude that Martian lava tubes have 10–1000 times the volume of terrestrial ones.

In 2014, Steve Jurvetson took this photograph inside a lava tube in Kona, Hawaii. The human remains found inside support the idea that humans used the interiors of lava tubes for shelter. On Mars, these lava tubes could be significantly larger, possibly aiding a human endeavor to settle on Mars. (STEVE JURVETSON / FLICKR)

The reduced Martian gravity enables these tubes to reach diameters of up to 300 meters (1000 feet), with significantly longer lengths.

This illustration shows a cross-section of a Martian lava tube. There is a solid basaltic wall/lining that is formed from hardened lava, while the liquid interior can be partially or completely drained away into an underground reservoir, creating the hollow tube. (MELISSAUSBURN / WIKIMEDIA COMMONS)

The tubes themselves, meanwhile, remain structurally stable.

A lava tube “skylight” on the Martian volcano Pavonis Mons, which opens to an underground cavern 35 meters (115 feet) across. When lava flows solidify on top but continue to flow in the liquid phase underneath, lava tubes can form. These underground rivers can later drain away, leaving an empty cavity inside. (NASA / JET PROPULSION LABORATORY / UNIVERSITY OF ARIZONA)

Once boulders, dirt, and debris are removed, they could provide essential environmental shelter.

A dust storm on Mars, a common occurrence during the Martian summers. These storms were first discovered by the Mariner 9 mission in 1971. While dust storms can pose severe habitability threats to humans on the surface, the interior of a lava tube should be sufficiently shielded from this threat. (NASA/JPL-CALTECH/MSSS, FROM MARS RECONNAISSANCE ORBITER)

Dust storms, external radiation, impacts, and temperature swings would all be greatly mitigated.

The Mars Curiosity rover not only gathers large amounts of scientific information from drilling, baking, and laser-shooting various locations on the Martian surface, but also takes spectacular photos. What you cannot see, but what it has measured, is that temperatures can reach as high as 70 F during daytimes, but fall as low (in the same location) as -100 F at night. (NASA/JPL/MSSS)

With a sustained supply of food, water, power, and pressurized, breathable air, Martian lava tubes could successfully host human settlements.

Nāhuku-Thurston Lava Tube, a natural formation that’s part of Hawaii Volcanoes National Park, is a spectacular example of a large lava tube found on Earth. Owing to the reduced Martian gravity, researchers determined that Martian lava tubes could reach approximately the volume of the Empire State Building, 10 to 1000 times the volume of terrestrial lava tubes. (NPS PHOTO/D. BOYLE)

The first humans to colonize Mars might be cave-dwellers, skirting the harsh surface conditions.

Astronauts practice for space using an analog cave environment in Sardinia. The European Space Agency program is called Cooperative Adventure for Valuing and Exercising human behaviour and performance Skills (CAVES) and has sent dozens of astronauts underground. (ESA-V. CROBU)

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.

Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.


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