Hello, friends!  Welcome to Our Place in Space: A to Z!  For this year’s A to Z Challenge, I’ll be taking you on a partly imaginative and highly optimistic tour of humanity’s future in outer space.  If you don’t know what the A to Z Challenge is, click here to learn more.  In today’s post, L is for…

LAVA TUBE HABITATS

The surface of Mars is not a safe place for humans.  Martian dust storms can be really scary.  The temperature fluctuates wildly from a bit too cold to waaaaay too cold, and there’s basically no protection against all the deadly radiation raining down on the planet from space.  Fortunately, humans in the distant future won’t need to live on the surface of Mars.  Mars is offering us free housing in the form of underground lava tubes.

Mars was once a volcanically active world.  In fact, the largest volcano in the entire Solar System is on Mars.  Lower gravity means volcanoes can grow much larger on Mars than they ever could on Earth.  But Mars hasn’t been volcanically active for a long, long time.  The volcanos stopped erupting and the lava stopped flowing billions of years ago.  Today, all those oversized Martian volcanoes are extinct, and all the lava tubes around them are now empty.

So what exactly is a lava tube?  Well, have you ever seen rivers of lava (either in real life or in videos) flowing down the side of an active volcano?  You know how the surface of these lava rivers starts to cool off, forming a blackened crust?  Eventually, this crusty surface lava will become thick enough and solid enough to form a roof over the lava river, while the rest of the lava continues to flow freely underneath.  This is how lava tubes form.

On Earth, lava tubes can get pretty large.  They can be wide enough and tall enough for multiple people to walk through them comfortably.  On Mars, lava tubes could (theoretically) be even larger—almost half a kilometer wide, perhaps!  Once again, this is because of the reduced Martian gravity, which allows all sorts of natural structures to grow larger on Mars than they ever could on Earth.

In the future, sections of these lava tubes could be sealed off and pressurized with air.  Dust storms could rage on the Martian surface while human colonists remain safely underground.  All that natural rock would insulate us against the extreme temperature variations on the surface, and the rock would also serve as a natural barrier against all that radiation raining down from space.  With relatively little effort, we could convert the smaller lava tubes into comfortable and cozy human habitats.  Or, using those half kilometer-wide tubes, we could build much larger and more robust human communities.

At the moment, though, finding lava tubes that would be suitable for human habitation is tricky.  Lava tubes are underground.  Therefore, fully intact lava tubes are not visible in photos taken by our orbiting space probes.  The only Martian lava tubes we currently know about are the ones where the roof has either partially or fully collapsed.  This leaves us with a bit of a Catch-22 scenario: any lava tube we can currently find is structurally compromised and, therefore, might not be suitable for human habitation.

But that seems to me like a limitation of our current Mars exploration program.  As NASA, the E.S.A., and other human space agencies send more and more orbiters, landers, and rovers to Mars, I’m sure new techniques (seismography, gravity mapping, etc.) can be used to find all the lava tubes hidden beneath the Martian surface.

Want to Learn More?

Here’s a short paper advocating for more research about lava tubes on Mars and also on the Moon.

And here’s a ten minute video from Fraser Cain describing what we currently know about Martian and Lunar lava tubes in more detail.