Fresh photos from NASA's lunar orbiter suggest that pit craters could provide havens for humans on the moon – just as they do in 50-year-old science fiction. About 10 candidate pit craters have been identified in high-resolution imagery from NASA's Lunar Reconnaissance Orbiter, according to Mark Robinson, the principal investigator for the orbiter's camera. He features images that appears to show sunlight slanting down at an angle into holes in the ground. "They could be entrances to a geologic wonderland," Robinson says in a NASA Science News report. "We believe the giant holes are skylights that formed when the ceilings of underground lava tubes collapsed." Over at Beyond the Black, space writer Robert Zimmerman offers up a provocative pair of pictures, showing sunlight hitting a pit crater at different times during the lunar day. These observations follow up on last year's first picture of a lunar skylight, based on data from Japan's Selene spacecraft. Such pit craters are thought to be a consequence of ancient volcanic activity on the moon, with surface openings leading to the lava tubes beneath. The tubes could provide shelter from the moon's harsh surface conditions. "The tunnels offer a perfect radiation shield and a very benign thermal environment," Robinson says. "Once you get down to two meters under the surface of the moon, the temperature remains fairly constant, probably around -30 to -40 degrees C." That's the equivalent of 20 to 40 degrees below zero Fahrenheit - pretty chilly, but not as inclement as typical temperatures at the lunar surface, which swing between 225 degrees above zero during the day and 250 below zero at night. You could even imagine sealing off the openings and creating a tunnel city. That's basically what Robert Heinlein did in his tales of Luna City, published as short stories and novels in the late 1950s and 1960s. Perhaps the best-known of these works is "The Moon Is a Harsh Mistress," one of my favorites. Robinson as well as moon maven Paul Spudis of the Lunar and Planetary Institute say more observations will need to be made to confirm what's actually within the pits. "Hold off on booking your next vacation at the Lunar Carlsbad Hilton," the NASA report quotes Spudis as saying. "Many tunnels may have filled up with their own solidified lava." If it does turn out that the caves of Luna are open for business, that might lead NASA's mission planners to reconsider their next steps for human exploration. But when it comes to pit craters, the moon isn't the only game in town ... or the solar system. Mars appears to have pits as well, including one that discovered by a group of seventh-graders only recently. As I mentioned a few days ago, the Martian caves around Arsia Mons are on the short list for potential human missions. The caves could be among the best places to look for signs of past or even present life on Mars. So when I say that life's the pits on other planets ... that's meant to be a good thing.
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