angus houston must have seen some map but there can be crevices and gullies. and the fact they are tracking the terrain. they are keeping 30 meters above the sea floor. if the sea floor takes a dive so does the vehicle. >> there is a crunch depth for the vehicle. the pressure could -- >> my understanding is that 4500 is their comfortable operating depth and they could get down to 4900. but you don't want to go near that boundary. >> it does raise the question whether they will be experiencing this kind of aborted mission frequently. >> it does. and i don't know if david knew how deep it was. and i heard him saying the programming of it. what other programming things have to be reset when it comes back up. we were talking about doing 18 square miles a day. at this rate there's no way they