The values from the newmars forum have no references, so I have no idea where they got them from (and they look extremely small and wrong - those are in "rems/day", mine are *rads per second*. The values I used are from a 2001 paper on the subject which I do reference, so I'd advise you to use those unless you can find a referenced source that's more accurate.Ganymede39;s magnetosphere doesn't provide much protection at all. If you look at the numbers I quoted, the radiation is focussed at Ganymede's poles (which is where the field lines of the magnetic field are coming in and so any particles trapped in them are bombarding the surface - that's why we get aurorae, because our atmosphere is in the way) and lower at the equator, but they're still deadly either way. The radiation anywhere on ganymede would still kill unprotected human (ignoring vacuum/temperature effects) in less than a minute - heck, even on Callisto a human would get a fatal dose in about two minutes.
As for digging underground, you only have to be exposed at the surface long enough to dig a hole to get under cover (or to shovel enough ice over yourself as extra protection) - once you've got that far then you can safely dig away with a metre or two of ice above your head - nuclear damper technology would also probably help too.
As for digging underground, you only have to be exposed at the surface long enough to dig a hole to get under cover (or to shovel enough ice over yourself as extra protection) - once you've got that far then you can safely dig away with a metre or two of ice above your head - nuclear damper technology would also probably help too.