The Cassini space probe spent 13 years circling Saturn, sending back data and stunning images of the planet and its moons.
It made nearly two dozen loops between Saturn and its rings before plunging to a fiery end in Saturn's atmosphere last September. Now, just over a year later, scientists have published 11 different studies based on the data from Cassini so-called Grand Finale.
Cassini project scientist Linda Spilker dedicated 30 years of her career to Cassini, starting when the project was just a concept at NASA. She’s at the Jet Propulsion Laboratory in Pasadena.
“If you think about it, 30 years is the amount of time it takes Saturn to circle the sun a single time,” Spilker said. “So I've worked on Cassini for one Saturn year.”
One of the most striking of Cassini’s discoveries was the beautiful sculpted edges of the gaps in Saturn’s rings, which are caused by its moons.
“And we got to see them from all different angles – on the lit side, the unlit side. Lots of really incredible data from Cassini,” Spilker said.
Another discovery that surprised Spilker was seeing a phenomenon they named ‘ring rain.’
“There are actually elements and particles falling from the rings,” Spilker said. “The rings are very slowly going away, falling into the planet, being hit by micro-meteoroids and broken apart. We're not sure exactly how long the rings will last, but it’s a very slow process.”
But if Cassini was doing such great science, why did NASA plunge it to its death in September 2017?
“Cassini was running out of fuel,” Spilker explained.
It was in danger of crashing into one of Saturn’s moons, Enceladus or Titan. Both have liquid water oceans underneath their icy crusts and are promising areas for future exploration.
“And we spent 22 orbits collecting brand new science, and then we got a distant nudge from Titan.
We call it Titan's goodbye kiss.”
That nudge sent Cassini plunging into the atmosphere of Saturn, vaporizing it at high speed.
“There was a mix of emotions,” Spilker said. “Basically, tremendous pride -- all that Cassini had accomplished -- and at the same time like saying goodbye to a good friend, someone that had been a part of my life for so long.”
Spilker’s not done with Saturn and its moons, though. One proposal would land a quadcopter on the surface of Titan. Another would send a probe to Saturn to study the noble gasses that Cassini couldn’t measure.
“I think it'd be great to go back with a mission fly very close to the rings and watch the ring particles interact,” Spilker said.
She'd also like to see an experiment that would check Saturn’s moons for signs of life.
“That would be a great mission,” she said.