Cue the X-file theme song, because there really is literally a hole in the Moon. Just published in the Geophysical Research Letters on November 16, a study details a new finding from photographs obtained during the 20-month mission of the Japanese lunar orbiter SELENE, better known as Kaguya, which ended last June when the spacecraft was intentionally crashed into the Moon.
The photos reveals a hole measuring some 65 meters wide located in the Marius Hills region, an area known for volcanic domes on the Nearside. The hole appears to be at least some 80-85 meters deep. Most craters of that width are generally only 15 meters in depth.
Several German researchers collaborating with the Japanese team have determined that the hole was not caused by a meteorite impact or volcanic eruption. They are speculating that the hole is most likely a skylight caused by the collapse of the top of a lava tube at some point.
While lava tubes are fairly common on Earth, these tubes have not found on the Moon raising questions about lunar volcanism. If the existence of the lunar lava tube is confirmed, then it will be the first such geological feature to be found on the Moon. The lava tube could also serve potentially as a site for a lunar base as noted in the editor's highlight to the article in GRL.
One of the true ironies of the Apollo program is that the Marius Hills was a targeted leading site for one of the Apollo lunar landings. The destination was originally proposed for Apollo 15 , but the commander of the mission Dave Scott indicated he preferred Hadley-Apennine site. The Marius Hills site got bumped to Apollo 16, then Apollo 18, and then rescheduled for Apollo 20. Apollo 18-20 were later cancelled. Had the hole had been discovered back in the early '70s, the find could have significantly altered the course of the Apollo program.
Source: Deep hole spotted on moon Science News
More sources: I have since found several more links to articles about this possible skylight published last month:
First Moon "Skylight" Found -- Could House Lunar Base? National Geographic
Found: first 'skylight' on the moon New Scientist
Note: As I have not used the 'Breaking' in a diary title for several months, please forgive me for using the term a little broadly this time around. The story obviously came out last week but was overshadowed by the discovery of a significant amount of water on the Moon by LCROSS. And no the site is not where the LCROSS impacted which occured near the polar region of the Moon.
Update: Thank you all for recommending this diary! :)