Update: Juno launched successfully at 1625 GMT on 5 August from
Cape Canaveral Air Force Station in Florida Jupiter is, quite
literally, the biggest mystery in the solar system. But that
will hopefully change after the launch of NASA's Juno mission on
Friday. About 15 years ago, NASA's Galileo mission revealed
curious inconsistencies in the planet's atmosphere. Models of
the solar system suggest Jupiter formed near its current
location, just outside the solar system's "frost line", a
boundary beyond which water vapour condenses. Yet when Galileo
launched a probe into the planet's atmosphere in 1995, the probe
found surprisingly little water. Did the probe hit a rare dry
spot on Jupiter? Or is all of Jupiter depleted in water? Juno
will try to find out by searching the planet for water's
signature at six different microwave frequencies, which will
reveal the molecule's concentration from the top of the
atmosphere to pressures of about 100 Earth-atmospheres. If the
whole planet is dry, our very understanding of