We said goodbye on Friday to one amazing adventurer. After 4.9 billion miles, 162 flybys, and nearly 300 orbits of one of our largest neighbors, Cassini plunged through Saturn’s upper atmosphere, sending out one final burst of data as it’s instruments took in a last gasp of Saturnian air. The Cassini team, some of whom have been with the mission since it launched in 1997, watched and waited until that moment of silence. No more transmissions – Cassini had broken up in Saturn’s atmosphere. It seemed a fitting end for the sturdy interplanetary explorer, though the moment was a melancholy one as well.
Cassini provided a trove of information over the years, and like all good scientists, raised as many questions as it answered. The debate over the age of Saturn’s rings still continues, though we now have a first hand look at how planetary bodies form. (Pity the poor moons trapped in Saturn’s rings, forever stuck in the infant stage of planetary development. They collect debris and try to grow larger, but Saturn’s gravity pulls it all apart again.) Cassini may have even given us a glimpse of the place most likely to hold life in our solar system. Saturn’s moon Enceladus turns out to have a flowing ocean of water under a frozen surface. Cracks in the ice near the southern pole allow water to escape into space, where it freezes and falls back to the surface. It also provides an amazing show for any spacecraft lucky enough to pass nearby.
Cassini’s fellow traveler, Huygens, even provided us with an up close and personal view of another of Saturn’s moons, Titan. The images that came back looked eerily familiar, with large looming cliffs, flowing rivers, and vast clouds in the distance. One might be forgiven for believing that the photos were images of the Grand Canyon seen through a yellow filter. But these canyons stood over rivers of liquid methane, and the thick cloud cover did indeed create a sky of orange. And those cobblestones that were strewn about the ground? Large nodules of frozen methane. Turns out it does rain on Titan, just not in a way we’re used to.
The main attraction, of course, was Saturn itself. After all, it was thought to be the only ringed planet for centuries, and even though we know now that other outer planets have rings, none are as well-defined or impressive as Saturn’s. The idea of slipping between those rings, to understand how they exist, has been the dream of many an astronomer.
And Saturn did not disappoint. Close-up, the rings are even more stunning. The complex and yet deceptively simple array of the rings is breathtaking. What would it be like, to be able to stand on the surface of Saturn and gaze up on those rings every morning? Thanks to Cassini, we have some idea of what that would look like. We have been to the other side of the rings, and we have seen the shadows they cast, the way the light reflects off their surface, the golden halo they create. We have looked at the rings from every possible angle, and we have learned that we still know almost nothing.
Ah, Saturn! It turned out the rings, for all their glory, where merely the appetizer. There’s the very odd hexagonal storm churning away over the North Pole. This is a storm so massive that two complete earths could fit inside and still not fill the space. It puts hurricanes here on earth to shame (and makes us very happy to be here rather than there). Another massive storm once spanned the entire width of the planet’s northern hemisphere, and only died when it ran into itself.
Still to be determined – the nature of Saturn’s core. How massive is it any way? Is Saturn just a big gaseous blob or is there more, another hidden piece we have yet to appreciate? Cassini’s final blocks of data will provide some answers and we can’t wait to hear what it had to say in those last moments.
So adieu, Cassini. Twenty years seems like such a young age, but you accomplished so much in that short time. You gave us an amazing view of Saturn’s kingdom, but more importantly, you inspired a sense of wonder in all of us. It would seem the god of the golden era had one last gift to bestow on mankind.