In December 1995,the Galileo spacecraft finnally arrived at the planet Jupiter. More than six years after it had been launched by NASA,the spacecraft's atmospheric probe, which had seperated from the orbiter four months earlier, plunged through the gas giants intense radiation belts and deep into its atmosphere. The onboard electronic systems had to be heavily shielded to protected them against the radiation and temperatures twice as hot as the Sun's surface. As the probe parachuted into Jupiter's atmosphere, pulled in by the enormous gravity, the orbiter passed close to the planet, receiving and storing information for later relay back to Earth . This was just the start of the Galileo mission - since 1995 ,the orbiter has been circling Jupiter and recording information about its weather and its planned - sized moons .
Before arriving at Jupiter, Galileo photographed the impact of Comet P/ Shoemaker- Levy 9 with Jupiter,the largest explosion ever seen in the Solar system. More recently,the spacecraft has photographed volcanic activity on the moon Io , and found evidence of water beneath the icy crust of another moon ,Europa.
Organic molecules thought to be from Mars were recently found in a 4.5 billion years old rock the fell into the Antarctic 13,000 years ago. Mineral features suggesting biological activity and possible microscope fossils of bacteria like organisms were discovered.
The main body of the spacecraft circling Jupiter is known as the Orbiter.The probe , on the left of the diagram ,descended into Jupiter's atmosphere. The probe consists of a descent module and a deceleration module , the later protects the former from excessive heat, seperating off and slowing the probes descent .
As it began its six year flight , galileo moved away from Earth towards Venus , then doubled back , using the gravitational fields of Venus and Earth to propel it toward Jupiter.
The orbiter and the probe split apart and the orbiter circles Jupiter , making approaches to all the planets large moons , It uses their gravity to change course and pick up speed with very little fuel .
The probe descended through Jupiter's atmosphere gathering data . The descent module split from the deceleration module and a parachute slowed its rate of descent . The module descended for 57 minutes before burning out .
The comet consisted of at least 21 discernible icy fragments with diameters estimated at up to two kilometres.
