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
Exploration of Mars years beyond their specification. As of 10 June 2018, two rovers were on the surface of Mars beaming signals back to Earth ("Opportunity" of the Mars Exploration Rover mission and "Curiosity" of the Mars Science Laboratory mission), with six orbiters surveying the planet: "Mars Odyssey", "Mars Express", "Mars Reconnaissance Orbiter", "Mars Orbiter Mission", MAVEN, and the Trace Gas Orbiter, which have contributed massive amounts of information about Mars. The stationary lander "InSight" is investigating the deep interior of Mars. No sample return missions have been attempted for Mars and an attempted return mission for Mars' moon Phobos ("Fobos-Grunt") failed. On