There's a LOT of radiation in those belts around Jupiter - "Europa receives about 5.40 Sv of radiation per day.[19] (5.0 Sv is already considered lethal acute dose) from Jupiter's large radiation belts (10 times stronger than Earth's Van Allen radiation belts), and is a severe health threat to colonists without adequate radiation shielding. The satellite has only a very weak magnetosphere, which leaves it exposed to radiation by Jupiter and also the solar wind."

From Wikipedia https://en.wikipedia.org/wiki/Terraforming_of_Europa#Magneti...