Exploration of Jupiter disadvantages for colonization because of the severe radiation conditions prevailing in Jupiter's magnetosphere and the planet's particularly deep gravitational well. Jupiter would deliver about 36 Sv (3600 rem) per day to unshielded colonists at Io and about 5.4 Sv (540 rems) per day to unshielded colonists at Europa, which is a decisive aspect due to the fact that already an exposure to about 0.75 Sv over a period of a few days is enough to cause radiation poisoning, and about 5 Sv over a few days is fatal. Ganymede is the Solar System's largest moon and the Solar System's only
Himalia (moon) a different moon may have been involved. Himalia (moon) Himalia is the largest irregular satellite of Jupiter. It is the sixth largest Jovian satellite overall in size, and only the four Galilean moons of Jupiter have greater mass. It was discovered by Charles Dillon Perrine at the Lick Observatory on 3 December 1904 and is named after the nymph Himalia, who bore three sons of Zeus (the Greek equivalent of Jupiter). It is one of the largest planetary moons in the Solar System not imaged in detail, and the largest not including the moons of Neptune and several trans-Neptunian objects,