The search for houses for the caves of Mars has already begun

The neighborhood is a wild card, and moving there will surely be expensive. But one of the best options for shelter when humans finally reach the red planet will be underground caves. These rocky hollows, which they exist in mass on both Earth and the Moonthey are natural buffers against the harsh conditions of Mars.

In a presentation this month at the Geological Society of America Connects 2022 meeting in Denver, researchers identified nine prime cave candidates worthy of future exploration. All of these grottoes appear to extend at least some distance underground and are close to accessible landing sites for a light rover.

These structures will provide respite from the challenging Martian environment, said University of Arizona geoscientist Nicole Bardabelias. “Everything on the surface is subject to hard radiation, it’s possible bombardment of meteorites or micrometeorites and very large day-to-night temperature swings,” he said.

To get closer to the most sought-after real estate properties on Mars, Ms. Bardabelias and his colleagues consulted the Catalog of Mars Global Cave Candidates. This compendium, based on images collected by instruments on board the Odyssey of Mars spaceship and the Mars Reconnaissance Orbiter, inventories over 1,000 candidate caves and other peculiar-looking features on Mars. (Think of this as Marcian’s first multiple listing service.)

Just as any discerning home buyer would filter search results on Zillow or StreetEasy, the researchers whittled down the catalog by imposing two criteria. First, they required a cave to be about 60 kilometers from a suitable landing site for the spacecraft. Second, they stipulated that high-resolution images would be available.

Ms. Bardabelias and his collaborators defined a suitable landing site as a site below an elevation of approximately 3,300 feet. These relatively low places are favorable landing sites because they give spaceships more time they slow down as they travel through the thin atmosphere of Marssaid Mrs. Bardabelias.

“Mars has enough of an atmosphere that you can’t discount it, but not enough to give you a significant amount of aerobraking,” he said, referring to using a planet’s atmosphere to slow down an incoming spacecraft. “If you don’t have enough space between when you hit the top of the atmosphere and where you’re supposed to land, it’s going to be very, very difficult for you to do the entry, descent and landing sequence correctly.”

The team also required that images of the upper platform be available for each cave candidate. Until the runners get closer to NASA Mars helicopter for Martian real estate photography, that honor belongs to HiRISE, or the High resolution imaging science experiment camera on board the Mars Reconnaissance Orbiter. Ms. Bardabelias is the chief operations engineer for HiRISE, which is capable of discerning Martian features about 3 feet across, but has so far captured less than 5 percent of the planet’s surface.

There were 139 apparent caves that met the team’s criteria, and Ms. Bardabelias and his collaborators manually examined the images of each. After disregarding features such as bridge-like rock formations that were obviously not caves, the team looked at the remaining pit-like features. The researchers concentrated only on those that appeared to extend some distance underground, yielding a sample of nine main cave candidates.

These possible caves, the largest of which has an opening that could swallow a football field, are worth a closer look, Ms. Bardabelias. But none of rovers currently operating on Mars they are close enough to explore any of these caverns, so that task falls, for now, to the spacecraft orbiting the red planet. HiRISE follow-up images taken from different angles and under different lighting conditions will reveal new details about these caves, Ms. Bardabelias. You can help the HiRISE team decide what to photograph next voting for your favorite cave.

We should be looking once more to the caves for refuge as we prepare to explore new worlds, said Glen Cushing, a space scientist at the US Geological Survey’s Center for Astrogeological Sciences and creator of the Mars Global Cave Candidate Catalog, not involved in the research. “This takes us all the way back to the dawn of humanity.”