With so much interest at the moment in finding and mapping caves off world, such as on Mars (see one sample document at http://www.asgsb.org/bulletins/v16n2/v16n2p121-131.pdf), what kind of equipment could possibly be used for this type of activity?
I was thinking about this earlier and considered whether radar could be used at different wavelengths to bounce of different materials at different depths, similar to the technique used for mapping the sea bed from orbit since people couldnt do this in person.
Then later robotic mapping using radar mounted on rovers before any kind of manned expeditions to do more detailed mapping.
It's a new area and I was interested to get views on how this could possibly be done.