Saturn probe’s suicide may solve final riddle

EVEN as Nasa’s Cassini probe hurtled towards its final, fiery destruction in the atmosphere above Saturn, controllers back on Earth were hoping it would reveal one final secret.

The 20-year mission to investigate the ringed planet and its moons had been hailed as one of the dazzling successes of space exploration, yet it had so far failed to solve one of Saturn’s most intriguing riddles: why the northern hemisphere has a shorter day than the southern. Scientists believe the answer lies in the mosaic of magnetic fields near the planet’s surface.

The only way to pass through them, however, was as part of a suicide dive.

Yesterday, as the 22-foot craft buffeted through Saturn’s upper layer of clouds, scientists at Jet Propulsion Laboratory in Pasadena, California, were left praying the machine could keep stable long enough to collect and transmit the vital data.

Teams will now spend months poring over the new information, but the early indications look positive – the probe was beaming back information right until the end.

“Cassini performed exactly as she was supposed to,” said Professor Jonathan Lunine, from Cornell University, New York, while Lord Rees, the Astronomer Royal, described the final descent as the “grand finale of the greatest scientific and engineering achievements in space exploration.”

Saturn’s out-of-sync hemispheres have baffled scientists since Cassini first spotted the variation when it arrived in 2004. While the northern hemisphere completes a full rotation in approximately 10.6 hours, in the south it takes 10.8 hours.

Dr Daniel Brown, an astronomer at Nottingham Trent University, said cracking this conundrum would yield insights into the science of planet formation in general.

Cassini discovered seven new moons, observed raging storms on Saturn, and shed new light on the planet’s famous rings.

One of the most significant findings was that of an ocean under the icy surface of Enceladus which may harbour life.

At almost every stage, the project has been supported by British scientists, including Professor John Zarnecki, president of the Royal Astronomical Society, who said: “The mission has not only been a wonderful scientific success, but has also shown what can be achieved when scientists and engineers from across the world can work together with a common purpose to realise lofty goals.”