Caves on Mars ?

RockDoctor writes: The BBC are reporting that the photo-surveying of Mars has revealed seven suspected cave entrances in the Arsia Mons volcanic area. This has been hinted at before — long sinuous channels in the same region have been interpreted as collapsed "lava tube" caves — but the scale of the suggested entrances (sheer drops of 80 to 130m from the surrounding surface) makes my troglodytic hands twitch for my abseiling gear. 130m would be a bit challenging for a successful base jump though ... hmmm ... ideas ... thin atmosphere ... rocket packs ...