Cassini starts its five final orbits around Saturn before final plunge

Scientists are hoping for one final burst of data from Cassini, a NASA spacecraft that has been studying Saturn for 13 years.

As the probe begins its final five orbits around Saturn, an astronomer whose career was inspired by the Cassini mission says she hopes its legacy will live on. 

Dubbed the Grand Finale, the final dives began on Monday and will end with Cassini's final death plunge on 15 September. Its closest approach to Saturn will be 1630km, and it will use its rocket thrusters to avoid crashing prematurely. 

No spacecraft has ever ventured this close to Saturn, which is the second biggest planet in our Solar System. It is surrounded by rings made up of ice and rocks, varying in size from a fingernail to a mountain. 

The Cassini probe reached Saturn in 2004, seven years after it set out on its journey. Next month, it will end its mission by crashing through Saturn’s atmosphere, burning up like a meteor. Read more.

With little left to lose, scientists are now daring to perform the final dives, which will better measure the planet’s magnetic fields and go further in understanding its structure. More knowledge on how Saturn was formed could help astronomers study other planets in the Solar System and beyond. The final dives will also gather more scientific data on Saturn’s rings, their mass and features. 

Affelia Wibisono, an astronomer at the Royal Observatory Greenwich, told Professional Engineering Cassini was the reason she studied planetary science. She said it’s a mission that was extended several times because it “keeps on giving”. 

“No one expected it to still be here 13 years after it got there,” Wibisono said. “For me, personally, it’s a bitter-sweet moment. Cassini discovered loads of great things. Hopefully, its legacy will continue and we will send more spacecraft to Saturn.” 


The gas giant (Credit: Nasa)

Over the course of its mission, Cassini discovered seven new moons orbiting Saturn and revealed amazing features about two of the better-known ones: Titan and Enceladus. On Titan, it studied the atmosphere and found rivers, lakes and sand dunes. The moon, with a temperature of 180 degrees Celsius, has several important similarities with what the Earth was like early on in its formation, explained Wibisono.

Enceladus, she said, is covered by an icy crust and has volcanoes that spew out ice instead of lava. The liquid water beneath those volcanoes, and the existence of hydrothermal vents, have given scientists a reason to search for creatures lurking in this alien world. According to Wibisono, the moon is “the best place to look” for signs of life in the Solar System.

Cassini’s project manager at NASA's Jet Propulsion Laboratory, Earl Maize, is confident the dives will go according to plan. “Thanks to our past experience," he's quoted as saying on NASA's website, "we understand how the spacecraft will behave at the atmospheric densities our models predict."

In a statement, Linda Spilker, a scientist working on the Cassini project, said that by plunging into Saturn's atmosphere, Cassini would become the first atmospheric probe of the gas giant. 

The craft has been locked into a collision course with Saturn to avoid damaging any moons or rings, and to make sure that future missions are not jeopardised.