As Nasa sends Cassini spacecraft to a spectacular death on Saturn, scientists describe delight and pride with mission

Andrew Griffin
NASA's Cassini spacecraft is shown diving through the plume of Saturn's moon Enceladus, in 2015, in this photo illustration: Reuters

Cassini, one of the world’s most daring spacecrafts, is about to die. But it will have lived a “bizarrely wonderful” life.

Right now, the craft is flying over the top of Saturn, gathering yet more information about the planet it has been circling for years. But within hours, its mission will come to an end.

The craft will be smashed into Saturn’s atmosphere, burning up and destroying itself, so that it doesn’t accidentally hit one of the planet’s moons and populate it with bacteria it carried back from Earth. Even that act of destruction will give us an unparalleled view of Saturn itself, as Cassini points itself towards the planet, taking pictures of it and sending back information right until its very last moment.

But before it does so, it will have shown us that the possibility of other life in our galaxy is far higher than we thought.

One of the biggest findings, for instance, was that the moon Enceladus could in fact support alien life, right within our own solar system. That was never even expected from a probe that was sent off to mostly look at Saturn, not its moons.

Cassini hasn’t just found things in our solar system, it has changed our entire view of Earth’s neighbourhood. It has filled it with the possibility of life and given us a better picture than ever before of our planet’s surroundings.

“Cassini has turned the moons of Saturn from dots of light into places, from Huygens landing on Titan, with its ice rocks and seas of methane, to the plumes of water being ejected from Enceladus, to bizarrely shaped moons like Hyperion and Pan,” said Dave Clements, an astrophysicist at Imperial College London. “It has shown us that the solar system is an even more bizarrely wonderful place than we had previously thought.”

The collision – which will happen around lunchtime in the UK on Friday – will bring to an end work by a huge range of people from 27 different countries, conducted over 20 years and collecting information that is stunning in its sheer quantity.

“In its 20-year mission, Cassini’s numbers alone are astonishing,” said Mathew Owens, professor of space physics at the University of Reading. “It’s discovered six moons, taken half a million images and returned nearly a terabyte of data that has underpinned more than 4,000 scientific papers.

“No doubt scientists will be analysing the information from its final, one-way trip into Saturn’s atmosphere for years to come. This has been a hugely successful mission and a testament to all involved.”

But those who worked on the mission say that there are no regrets – and that the mission actually did far more than was ever expected before it set off.

“We went there with certain questions,” said Caitriona Jackman, associate professor in physics and astronomy at the University of Southampton. “We wanted to chart the magnetic field of the planet, we wanted to examine the moons, we wanted to land on Titan – which we did successfully – but we’ve also had many surprises.

“For example, in charting the moons of Saturn we discovered many more moons and we also discovered that one of the moons – Enceladus – is producing geysers of water vapour from cracks on the surface. Such unexpected discoveries can change the course of a mission.

“I think it is important to emphasise that the mission doesn’t end on 15 September in the sense that the data will be there and will be actively analysed for many, many years to come.”

Like Dr Jackman, many of the UK’s scientists have a mixture of sadness that the mission is coming to an end and excitement about picking through the new data that will be sent back as it does so.

“The Cassini mission has been a tremendous adventure,” said Marek Kukula, public astronomer at the Royal Observatory Greenwich. “It’s completely changed our understanding of Saturn while sending back a stream of astonishingly beautiful images of the planet’s clouds, rings and moons, allowing us to feel almost like we’re out there with the spacecraft. I’ll definitely shed a tear when Cassini sends its last data back to Earth but I’ve no doubt that the achievements of the mission are going to be celebrated for decades to come.”

And for some, that excitement was tinged with more than a little tiredness. While the last few months have seen the mission send back unique, unanticipated findings, they’ve also been incredibly intense for all of the scientists looking to interpret them, said Michele Dougherty, professor of space physics at Imperial College London.

“I have a mixture of emotions; sadness that it is coming to an end, we have worked together so well and have produced such spectacular results and I feel so privileged to have been a part if it; real pride at what we have achieved over the years but also some feeling of relief now, the last six months have been very intense and I am pretty exhausted!”