Jupiter, the biggest planet, contains 75% of all the non-solar matter in our solar system. Is it a star that failed to become big enough to ignite, or is it a planet that was too big to solidify? Is the Gas Giant an essential protector of life on Earth, pulling asteroids and other space junk into its orbit, instead of letting them drift around and possibly hit our planet? Why is it surrounded with lethal radiation? Does studying the moons of Jupiter -- especially the ice covered Europa and the Volcanic -- teach us much about how Earth itself was formed? And does the study of these bodies teach us about the behavior of the Earth, for example increasing our understanding of earthquakes such as the ones that recently hit Japan?
NASA's first Jupiter mission; Galileo -- launched in 1989 from the Space Shuttle Atlantis; arrived at Jupiter in 1993, and ended up plunging into the Jovian atmosphere in 2003 -- gave us some partial answers. The men and women who controlled Galileo did an outstanding job keeping the crippled probe operating for as long as it did. The mission was an example of NASA's Science team at its best.
The newest Jupiter mission is called Juno; it is scheduled to be launched from Florida on an Atlas V rocket in August, and to arrive at its destination in July 2016. Its orbit will provide scientists with their first look at Jupiter's North and South poles. Compared to Galileo it is a fairly modest spacecraft whose sensors are limited in both capability and cost. Juno is what NASA calls a "New Frontiers"-class mission, those whose costs are capped at 1.1 billion dollars.
If all goes well, the next mission to Jupiter after Juno will be launched sometime around 2020. Planetary scientists at the National Research Council, as part of their "Dacadal Survey," apparently decided that they wanted, as their number two priority (number one is a Mars Sample Return mission), to launch a new "Flagship" mission to Jupiter. Called the Jupiter Europa Orbiter (JEO), this probe is currently estimated to cost about $4.7 billion. If funded, this mission would be carried out in close collaboration with the European Space Agency (ESA).
This new probe would first go into orbit around Jupiter and fly by a number of the Jovian Moons. These maneuvers would slow the spaceship down enough so that after two and a half years it would enter orbit around Europa. Once there, it would use a special set of instruments to study the ice sheet and to examine what scientists believe to be the ocean of liquid water within Europa.
Unfortunately, it looks as if neither NASA nor ESA will have the funds needed to begin work on this mission, or any other "Flagship" mission, any time soon. Space budgets are tight all over the world, and NASA is engaged in a tug of war with Congress over the future of America's manned space program. Funding for space science may end up as a collateral victim of this fight. Flagship missions require large investments, but they do pay major dividends in both science, technology, and even consumer products. Until this year, planetary scientists were counting on NASA's being able to fund at least one of these Flagship missions this decade, but the Obama administration's recent proposed cuts to NASA's science funding, and the ongoing fight over the whole federal budget, makes it doubtful that the US space agency will be able to find the money to begin work on the Jupiter Europa Orbiter mission in 2011 or 2012.
It would be a sad day indeed for America if our current political and budgetary difficulties were to prevent us from beginning work on what could be an exciting and valuable program,which, if it is successfully launched will probably be providing important information about our local cosmic environment until at least 2029, if not beyond.