|MadSci Network: Astronomy|
Hi Jen! A good place to start finding Callisto information is at the Nine Planets website: http://www.seds.org/nineplanets/nineplanets/callisto.html Humans have, of course, already sent probes to study Callisto. The last of these, Galileo, is still in orbit around Jupiter and has produced enormous amounts of new data on that planet and its satellites. So we certainly have the technology to launch craft to Jovian orbit and conduct robot operations there. However, your question seems to suggest whether we could send people to study Callisto. Using today's technology, the answer would be a borderline "yes": but it would be an extraordinarily difficult and costly venture, difficult if not impossible to "sell" to politicians or the public. To date, no humans have ever travelled beyond 400 000 km from the Earth - and Callisto is 1500 times further away. Three cosmonauts survived over a year in low Earth orbit, with regular supply craft supporting their needs, but Galileo took nearly six years to reach Jupiter (having used flybys of Venus and the Earth, twice, to boost its speed and reduce its need for propellant) and Galileo is, of course, a one-way trip: there are no plans to bring it home. No doubt any potential space travellers to Callisto would prefer to come back! In practical terms this means that they would have to carry return propellant with them, plus all their life support and logistical needs for at least twelve years. Solar flares and the immense radiation fields of Jupiter would require heavyweight shielding, and scientists have little evidence on how weightlessness would affect the body over a decade or more. Galileo masses just over two tonnes in Jupiter orbit, and was launched with a rocket stage from the space shuttle Atlantis in 1989. Any manned craft would necessarily mass hundreds of times more than this, and would require multiple shuttle launches to assemble the craft in Earth orbit. So the answer is yes, it would be technically feasible to send people to Callisto, using today's technology, but it would be extremely difficult. Finally, there's other "real estate" near by that would help prepare explorers for long range journeys like this: long-duration bases on the Moon, trips to Mars and near-Earth asteroids would be essential to gain experience and the technologies needed for future deep space explorations. Regards, Andy Goddard
Try the links in the MadSci Library for more information on Astronomy.