[rosser]

If you want to colonize Europa, you'll have to dig a lot deeper than on Mars or the moon. Cosmic ray dosage on the lunar surface is around 30 rem/year. On Mars, it averages 50.

On Europa, it's around 500-600 rem per day. That's a fatal dose.

[tjmc]

Indeed it is. Colonizing the surface of Europa would be madness without serious shielding. What's the dose under a 200m thick ice sheet though?