In 1997, we sent out a spacecraft called Cassini, which reached the most beautiful planet in our Solar System – Saturn – in 2004. For the last 13 years, it has been orbiting the planet and sending back astonishing data. Cassini also had on board a lander called Huygens, which landed on Titan, the largest of Saturn’s moons in 2005, the first landing ever on another planet. It survived for only a few hours but Huygens changed our understanding of Titans, such as the existence of liquid hydrocarbon lakes on it.
Now after almost 20 years out there, the Cassini Mission has reached its grand finale. Starting in April 2017, Cassini has been undertaking daring orbits around Saturn. Subsequently, after a few more close flybys of Titan, it began weekly dives into the inner fringes of Saturn’s rings. On September 11, 2017, Cassini met Titan for the last time.
Today, September 15, 2017, it will plunge into Saturn’s atmosphere. And like a trooper that it has been, it will continue to send back data till the very end, until it loses contact with Earth and burns up to become part of Saturn itself.
“The spacecraft’s final signal will be like an echo,” said Earl Maize, Cassini project manager. “It will radiate across the solar system for nearly an hour and a half after Cassini itself has gone.”
The reason for this dramatic ending is that Cassini was running low on rocket fuel used to adjust its course. And its data has revealed that two of Saturn’s moons: Enceladus and Titan have the potential to contain habitable environments. If the spacecraft runs out of fuel, it will not be possible for mission control to adjust its course; and there is a possibility that it may collide with one of these two moons, thus contaminating them for future missions. In order to avoid this eventuality, NASA has chosen to safely crash it into Saturn.
Even though the mission ends today, the data and observations it has sent back will continue to provide new information about Saturn, its moons and rings for decades. Already the information it has given us has changed our perception of our solar system, Saturn and its satellites completely. We know that there are icy plumes on Enceladus; the rings are active and dynamic, and much more.
And all this time while it was looking at Saturn, Cassini also took the time to look back at us. On July 19, 2013, in an event celebrated the world over, it slipped into Saturn’s shadow and turned to take images of the planet, seven of its moons, its inner rings – and, in the background, our home planet, Earth. For the first time ever, people of Earth were told in advance that their photo would be taken from such a great distance. So, a lot of us looked up at the right time, all over the world and smiled and waved. This has been termed ‘The day the Earth smiled’. The picture once again showed us how small, how inconsequential we are from the perspective of the universe.
These have been a thrilling 13 years and with more information to come, who knows what else will be revealed. But for now all we can say is: Goodbye Cassini, you have done well.