Cassini readies final plunge into Saturn

WASHINGTON: Nasa’s Cassini probe is counting its final hours before one last plunge into Saturn on Friday that will cap a fruitful 13year mission that greatly expanded knowledge about the gas giant.

While orbiting Saturn nearly 300 times, Cassini made major discoveries, such as the liquid methane seas of the planet’s giant moon Titan and the sprawling subsurface ocean of Enceladus, a small Saturn moon.

“Cassini-Huygens is an extraordinary mission of discovery that has revolutionized our understanding of the outer solar system,” said Alexander Hayes, assistant professor of astronomy at Cornell University.

Data collected by Cassini’s spectrometer while passing through a vapour plume at Enceladus’s south pole showed hydrogen shooting up through cracks in its ice layer.

The gas was a sign of hydrothermal activity favourable to life, scientists said in April when they unveiled the finding.

Launched in 1997 and equipped with a dozen scientific instruments, the 2.5-tonne probe entered Saturn’s orbit in 2004, landing on Titan in December of that year.

On April 22, it began the manoeuvres for its final journey.

Moving closer to Titan, the spacecraft took advantage of the massive moon’s gravitational push to make the first of 22 weekly dives between Saturn and its rings — venturing for the first time into the uncharted 1,700 mile (2,700 kilometre) space.

Cassini’s last five orbits will take it through Saturn’s uppermost atmosphere, before a final plunge directly into the planet on September 15.

Cassini flew by Titan one last time on Tuesday before transmitting images and scientific data from the flight. Mission engineers will use the information gathered from the encounter they dubbed “the goodbye kiss” to make sure the vessel is following the right path to plunge into the gas giant’s atmosphere.

“The Cassini mission has been packed full of scientific firsts, and our unique planetary revelations will continue to the very end of the mission as Cassini becomes Saturn’s first planetary probe, sampling Saturn’s atmosphere up until the last second,” said Linda Spilker, Cassini project scientist at Nasa’s Jet Propulsion Laboratory in Pasadena, California.

Cassini is expected to lose communications with Earth one or two minutes into its final dive, but 10 of its 12 scientific instruments will be working right up until the last moment to analyse the atmosphere’s composition.

That data could help understand how the planet formed and evolved.

On the eve of its final descent, other instruments will make detailed observations of Saturn’s aurora borealis, temperatures and polar storms. — AFP