The Cassini spacecraft will go out in a blaze of glory crashing into Saturn

Thanks for the memories (e.g. methane lakes and new moons)

The Cassini spacecraft has been an incredible success. It launched almost 19 years ago on a mission to visit Saturn and explore its many moons. To get there it needed to spin around Venus in 1998 and once again in 1999 for the gravity assist. It did the same to Earth and then Jupiter on its voyage across the solar system. The scientific riches delivered by the mission can’t be overstated. For nearly 12 years Cassini has made breathtaking discoveries and changed many of our assumptions about the solar system. With its fuel running out, Cassini’s mission is nearly over but it’s going to go out with a bang.

Discoveries

Other spacecraft had already visited Saturn before Cassini, most famously Voyager 1, but no other mission has spent so long and explored in so much detail. In 2005, Cassini dropped the Huygens probe onto Titan, letting us investigate its amazing lakes of liquid methane. This was the first time we landed a spacecraft anywhere in the outer solar system. Cassini has investigated epic storms on the gas giant and visited many of its moons, discovering several we didn’t even know about.

Daphnis, a moon discovered by Cassini in 2005, orbits Saturn within its rings. Image © NASA/JPL/Space Science Institute

The scientific value of the mission is obvious but Cassini has also gifted us with incredible images from the ringed planet. We’ve seen the sun glistening on the lakes of Titan, geysers erupting into space from moons hiding salty oceans, and we’ve seen storms the size of Earth. There was also The Day The Earth Smiled. In 2013, NASA turned Cassini to take images of Saturn and Earth together. For a change, NASA alerted the public to the event in advance so that people around the world could look up and wave at the same time. Hi Cassini!

The Day the Earth Smiled. This composite image of Saturn also features Earth as a tiny blue globe to the bottom of right Saturn, between the planet and the blue region of rings. Earthlings were told in advance about the photograph and were asked to smile and wave. Image © NASA/JPL-Caltech/SSI

Destruction

Cassini’s mission will be over in 2017 and the spacecraft has to be destroyed. As we’ve discussed before, the moons of Saturn are among the best places to search for life in the solar system. Cassini might accidentally be carrying organisms from Earth and we can’t risk leaving it in case it crashes and contaminates other worlds. If there is life out there, we don’t want to introduce Earth organisms to the mix in case it does damage. If there isn’t life out there, we don’t want to accidentally colonise a world without Earth organisms and then mistakenly think we’ve found evidence of extraterrestrial life. So Cassini has to go and NASA are already preparing for its final daredevil mission.

Even in its destruction Cassini will provide invaluable scientific data. Next year the mission will move into a finale programme fittingly named Grand Finale as chosen by the public. Between April and September 2017, Cassini will do something no other spacecraft has ever done: fly between the planet and its rings. What’s more, it will do this 22 times at incredible speeds. The following image shows the planned orbits.

Image © NASA/JPL

On its orbits, Cassini will fly closer to the surface of Saturn than ever before and make important scientific observations the whole time. We’ll learn more about Saturn’s gravity and magnetic fields, its rotation rate, and even its core. Cassini will also measure the mass of Saturn’s rings using gravity measurements. On September 15th, at the end of its 22 orbits, Cassini will destroy itself by plunging into Saturn still sending back messages about what it encounters.

Perhaps best of all, we’re going to get images back from Cassini as it does all of this. We’re going to see the rings close-up in high resolution, from Saturn’s point of view and the Sun in the background. We’ll miss the years of discoveries Cassini gave us but what better way to finish the mission than to answer some of Saturn’s remaining mysteries, send us the best desktop wallpapers ever, and then burn in a blaze of glory?


Main image © NASA/JPL/Space Science Institute