Astronomers bid farewell to $3.9 billion Saturn spacecraft

Tampa : Global astronomers bid farewell Friday to NASA's famed Cassini spacecraft, which launched 20 years ago to circle Saturn and transformed the way we think about life elsewhere in the solar system.

Cassini, an international project that cost $3.9 billion and included scientists from 27 nations, has run out of rocket fuel as expected after a journey of some 4.9 billion miles (7.9 billion kilometers). 

Its death plunge into the ringed gas giant -- the furthest planet visible from Earth with the naked eye -- is scheduled for shortly after the spacecraft's final contact with Earth at 7:55 am (1155 GMT).

Cassini's well-planned demise is a way of preventing any damage to Saturn's ocean-bearing moons Titan and Enceladus, which scientists want to keep pristine for future exploration because they may contain some form of life.

"It will be sad to see Cassini go on Friday, especially as the instrument we built is still working perfectly," said Stanley Cowley, professor of solar planetary physics at the University of Leicester.

"But we recognize that it is important to bring the mission to an end in a tidy and controlled manner."

Three other spacecraft have flown by Saturn -- Pioneer 11 in 1979, followed by Voyager 1 and 2 in the 1980s.

But none have studied Saturn in such detail as Cassini, named after the French-Italian astronomer Giovanni Domenico Cassini, who discovered in the 17th century that Saturn had several moons and a gap in between its rings.