Caves on Mars?

RockDoctor writes "The BBC is 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."