After nearly 20 years in space and a final series of dives through Saturn’s ring, the spacecraft Cassini is on its last descent. It will crash into the planet later today, ending an incredible scientific mission to an amazing place.
Cassini and its instruments helped investigate Saturn’s atmosphere, its rocky rings, its strange polar hexagon. It also expanded our knowledge of Saturn’s moons, from the geysers and hidden oceans of Enceladus to the rocks and lakes on the surface of Titan. Cassini’s Huygens probe, which landed on Titan, was the furthest space landing of anything humanity has built.
Originally launched in 1997, Cassini’s mission was supposed to end in 2008. But it received two major mission extensions, nearly doubling its lifetime. It has sent 635 gigabytes of data back, which mightn’t sound like a lot except that all of it was on 1997 era technology, through a billion kilometers of space.
The spacecraft is being crashed into Saturn because it’s running out of fuel for orbital maneuvers, and scientists don’t want to risk accidentally crashing it into one of Saturn’s moons which might contain life, and contaminating them. I feel personally invested in Cassini’s mission and final resting place, because my signature is on board! When I was growing up, one of my Girl Scout troop leaders was an astrophysicist working on the Cassini Plasma Spectrometer before the spacecraft was launched. She arranged for us to all come in and get to see some of the instruments, and in the end our signatures were all added to the 600,000 signatures on the disc of human culture that was included with the spacecraft. This disc, modeled on the Golden Record aboard Voyager, is a time capsule of human culture for other spacefaring civilizations to find. But while the Voyager discs are traveling beyond our solar system, Cassini will be meeting its end here, to become part of the planet it studied.
Cassini’s voyage has been such an inspiration, a feat of technical and scientific exploration which I, along with millions of others, have loved watching from here on Earth.