Since the Voyager probes sped by in the 1980s, Jupiter has been visited by several human probes – most significant among them Galileo, which was specifically sent to the giant planet and conducted six years of research there been 1995 and 2003. Galileo ended its mission by by deliberately crashing into Jupiter’s atmosphere, where it would have disintegrated due to friction or been crushed by gravity (or some combination of both). Since then, scientists have been hoping to repeat their success with another major probe mission, of which the first, Juno, is expected to launch in 2011. At the moment, however, only two missions have proceeded beyond the concept stage and have some real likelihood of being launched.
2011: JUNO (NASA)
NASA’s new Juno space probe should have been launched last year, but has been delayed due to budget cuts. Juno is the next most ambitious space probe after successful expeditions to Jupiter (Galileo), Saturn (Cassini), and Pluto (New Horizons). Assuming it launches on schedule, it will reach Jupiter five years later, in 2016, and then begin a minimum two-year research mission. One of its principal objectives will be studying Jupiter’s atmosphere, looking for water and oxygen. It will also investigate the planet’s magnetic field, gravitational field, and – hopefully – get a sense of its internal core, which is believed to be a roughly Earth-sized rocky sphere.
Juno will also be testing a new power system. Previously, all space probes to the outer solar system operated on nuclear power, because the Sun’s light is too weak at such great distances to allow a solar-powered probe to operate effectively. However, solar panels have become sufficiently efficient in recent years that NASA plans to operate Juno on solar power. The far more expensive nuclear generators will therefore be conserved for other, equally ambitious projects.
2020: EUROPA JUPITER SYSTEM MISSION (NASA and ESA)
In 2020 (or thereabouts), NASA and the European Space Agency plan to launch a joint probe to Jupiter, currently called the Europa Jupiter System Mission (EJSM). Closer to launch, as is common for such missions, a more imaginative name will be selected. EJSM will actually consist of several independent components, launched to Jupiter together before splitting up to carry out their separate missions: a European probe sent to the moons of Ganymede and Callisto; an American probe sent to Io and Europa; and, possibly, Russian and Japanese probes to Europa and Jupiter itself, respectively. If the Russian project is ever completed, it would include a lander that would study Europa from its surface. They are also considering launching their Europa probe independently, though this seems particularly unlikely given perennial budget shortages in the Russian space program.
The overall objective of EJSM, like most of the more recent missions to Mars, is to assess the likelihood of life evolving in the Jupiter moon system. There have been several hypotheses put forward in the last fifty years which can be tested by this mission, including subterranean oceans on Europa and Ganymede. NASA is testing ideas for a submarine called Endurance, which might one day be capable of drilling through the surface of Europa and then exploring its underground ocean.
The ESA is currently considering several ambitious projects for the next decade, and it remains possible that the EJSM will be cancelled in future funding cycles.
CANCELLED MISSIONS
As with most planets, Jupiter is beginning to collect a significant number of proposed probe missions which, for budgetary reasons, have been either cancelled or indefinitely postponed. Such dead missions have been put forward by all three major space powers – the United States, Russia, and the European Union. For example, a mission to Jupiter’s moons – referred to as the Jupiter Icy Moons Orbiter – was developed before being officially cancelled in 2005. Prior to that, another moon project, the Europa Orbiter, had also been developed and then cancelled. Various concepts for a Europa mission remain, chiefly to investigate the suspected presence of a subterranean ocean on that strange moon.
