Exploration of Jupiter reach Europa after a 6.5 year cruise. The spacecraft would fly by the moon 32 times to minimize radiation damage. Because of the possibility of subsurface liquid oceans on Jupiter's moons Europa, Ganymede and Callisto, there has been great interest in studying the icy moons in detail. Funding difficulties have delayed progress. The "Europa Orbiter" was a planned NASA mission to Europa, which was canceled in 2002. Its main objectives included determining the presence or absence of a subsurface ocean and identifying candidate sites for future lander missions. NASA's "JIMO" ("Jupiter Icy Moons Orbiter"), which was canceled in 2005, and
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