Click for full figure.

In a new paper detailing work they first began in 2019, scientists have now carefully mapped the extensive lava tubes that appear to radially descend westward from the caldera of Alba Mons, the volcano on Mars that has the largest surface area but with a relatively low peak.

The mapped population of 331 lava tube systems has a mean length of 36.2 km, with a total length in the western flank geologic map quadrangle of ∼12,000 km. Individual lava tube systems extend up to ∼400 km, and it is likely that some of our mapped lava tubes are connected such that the total number is actually smaller and lengths (average and maximum) longer.

The map above, figure 10 of their paper, shows volcanic ridges as yellow, collapsed lava tube segments as red, and collapsed lava tube on the volcanic ridge as maroon. The wider map below, shows where this region is located, and gives the larger context.

The white rectangle on Alba Mons’ western slopes marks the area covered by the map above.

The scientists estimate that these tubes formed approximately two billion years ago. More important, the evidence suggests that long sections of the tubes remain intact.

This suggests that Alba Mons may host numerous targets for astrobiological exploration with a range in specific conditions (elevation, latitude, and degree of connectivity to the surface), some of which might promote habitability. Lava tubes are most readily thought of as exploration targets for the access they may provide to a sheltered near/subsurface environment. Lava tubes may be loci of both volcanic heat and depressions that collect or concentrate water or ices. The collapse features observed along lava tube systems on the western flank of Alba Mons provide an abundance of these, but the uncollapsed extents of the lava tube systems could facilitate exploration through near-surface drilling of subsurface cavities partially to nearly completely sealed from the Martian surface. [emphasis mine]

This region is located about 750 miles east of the candidate landing zone for SpaceX’s Starship spacecraft, and sits smack dab in the middle of the mid-latitudes where orbital data has found extensive glacial features. Thus, these tubes, especially those sections sealed from the outside world, could harbor large quantities of water ice.

Though lots of near surface ice has been found at the Starship landing zone, any human colony there will need to do a lot of construction to create protection from radiation and sealed environments for the colonists. The lava tubes however would provide natural shielding from radiation, an interior space that can quickly be sealed, and a less harsh thermal environment, since the temperature would not experience the day/night cycle.

Putting a colony in these tubes however will likely involve politics. Because, as the paper notes, these tubes might also be ideal locations for finding past (or even existing) Martian life, there is going to be opposition should anyone want to put a colony within them. Scientists will fear contamination, both of that Martian life as well as the humans who make contact with it. Others will want to protect that Martian life from any contact. And of course there will be a third group who will oppose any exploration there, merely out of fear.

I suspect it will be the Martian colonists themselves who will eventually move into this region, and they will do so when they decide they are self-sufficient enough to ignore the oppressive dictates of their rulers on Earth.