After 14 years and three billion miles, Galileo is sent on a suicidal mission into Jupiter's swirling storms

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The Independent Online

The Galileo space probe - which sent back the first stunning close-up images of the moons of Jupiter - finally ended its mission yesterday with a suicide plunge into the storms and clouds that shroud the largest planet of the solar system.

After 14 years and almost 3 billion miles of space travel, Galileo, as instructed, dived into the swirling gases that surround Jupiter and burnt up as it entered the atmosphere just before 7pm.

After months of inactivity since the mission was officially wound down in February, Galileo was reactivated to transmit during its final hours, providing what scientists hope will be vital new material on Jupiter's stormy atmosphere. The last burst of information reached Earth about an hour after its destruction, the time taken for the radio signal to travel at the speed of light.

Dr Claudia Alexander, the Galileo project manager at Nasa's Jet Propulsion Laboratory in Pasadena, California, said: "It has been a fabulous mission for planetary science, and it is hard to see it come to an end.

"We're keeping our fingers crossed that, after traversing almost 3 billion miles and being our watchful eyes and ears around Jupiter, Galileo will still give us new information about Jupiter's environment even in its final hour."

Scientists decided to end Galileo's mission in this fashion because, as it finally ran out of fuel and power, it could have risked collision with Europa, one of the moons it has studied and thus contaminate the planet with microbes from Earth. Unlike other Nasa probes, Galileo was not "cleansed" before take-off because it was expected to remain in orbit and scientists are concerned that some bacteria might have survived on board.

Scientists now believe, largely through information gathered by Galileo, that underneath Europa's 15-mile thick ice crust are salty, warm-water oceans that could support life, or might have done so in the past. Contamination by microbes from Earth would prejudice any future attempt to investigate Europa.

The Galileo mission is now considered to be a huge success, although there were setbacks at the beginning. Its launch in 1989 from the Space Shuttle had been delayed by the Challenger disaster and there were other technical problems on its way to Jupiter, which it reached in 1995.

But in the past seven years Galileo has given scientists a new understanding of Jupiter and particularly its moons, discovered by the astronomer Galileo Galilei in 1610, and the mission was twice extended.

Sending a "weather probe" deep into its murky atmosphere, Galileo made extensive observations of Jupiter's equatorial cloud belts and circulating ovals of clouds, some of which have long lifetimes.

But its real discoveries have been about the planet's moons. During its first orbit, Galileo passed Io and revealed how the tiny moon had changed since the Voyager fly-by of 1979. In particular, close-up images of the Ra Petara volcano showed sulphur lava flows emerging from a central caldera. On its final orbit, Galileo observed Io's most powerful volcano, Loki, in infrared light, seeing freshly exposed material on the shores of a lava lake.

Information was also gathered on Ganymede and Callisto, ice-covered moons, as well as data on some of the many other small moons that orbit the planet.

Fred Taylor, a professor of physics at Oxford University, said: "Galileo has provided a fantastic database that will be a rich source of progress in the planetary sciences for years or decades to come."

As one chapter of space exploration closes, another opens. The Cassini space craft - a sister ship to Galileo named after another early astronomer - is on its way to Jupiter's neighbour, Saturn, carrying the European Space Agency's Huygens probe. When it arrives at the ringed giant next July, it will begin a four-year tour of the planet and its moons, including the largest, Titan.