One of the requirements for the LROC mission is to supply NASA with data for evaluation of Constellation Program landing sites. Information, like the locations of potentially useful lava tubes, will be included in this information and used to select Constellation landing and outpost sites.
Ian: Is there any indication to suggest the Marius Hills skylight could access an underground network of tunnels?
Carolyn: It is hard to say whether the MHH might access an underground network of tunnels. It is a possibility, because we know that lava tubes on Earth can be many kilometers long.
In the paper, using geometry, we calculated that the tube width might be on the order of 370 meters, but it could be anywhere from meters to kilometers long. Remote observations cannot answer this question for us - it's like we're trying to see an entire room by looking through a keyhole.
Ground-based exploration could answer this question. For example, Haruyama and Japanese colleagues, including Hideaki Miyamoto (also a co-author), have tested whether ground penetrating radar (GPR) might be useful in detecting intact sub-surface lava tubes. They tested their technique at Mt. Fuji, and were successful. It would certainly be interesting to do a GPR study in any region of the Moon where lava tubes might be present!