Wisdom Of The Week

Why explore extraterrestrial caves? Partly for the same reasons scientists venture into caves on Earth. They’re protected from weather and (on other worlds) from meteoric bombardment, so their geological formations serve as frozen records of the planet’s past. Then there’s the life question. Liquid water on Mars is likely to exist underground, at depths where ice is melted by warmth from the planet’s interior. In caves, the temperature stays relatively stable, so they would also offer refuge from the 200-degree Fahrenheit day-night swings on the surface. Most important, they offer protection from radiation. Since Mars’ protective magnetic field flickered out eons ago, the constant barrage of cosmic rays on the surface likely would have destroyed any exposed critters. If life moved underground to escape, caves are a good place to look for fossil evidence of their tenancy. It’s even possible that in some Martian caves, life still exists.

“This is where the action is in terms of exploration,” says Penny Boston, a veteran cave scientist who just left the New Mexico Institute of Mining and Technology to become director of the NASA Astrobiology Institute, the agency’s focal point in the search for extraterrestrial life. Recently she’s been a leading advocate for what may strike many as a novel idea: that the ideal place to search for alien biology is not on the Martian surface, where NASA’s rovers have been looking, but beneath it.

- Mars, Underground: Looking for life on other planets? Go deep