As the Cassini mission to Saturn ends, its lead imaging scientist recalls her favorite photographs and moments
A SPECTACULAR SPACE exploration mission will conclude with a dramatic death. The Cassini spacecraft will self-destruct by plunging into Saturn’s atmosphere, ultimately burning up and disintegrating. The planned mid-september dive will be the nal farewell for a nearly threedecade-long collaboration between NASA, the European Space Agency and the Italian Space Agency. It’s been good while it lasted, Saturn.
The Cassini spacecraft launched aboard a Titan Ivb/centaur rocket from Cape Canaveral in Florida on October 15, 1997, and spent seven years en route to its target, Saturn. It entered orbit around the ringed planet in 2004 for what was intended as a four-year mission, but was twice extended for a total run of 13 years, or nearly 20 if you count the journey there.
Cassini completed the rst in-depth reconnaissance of Saturn, its moons and its rings. When the mission dropped the Huygens probe on Titan, it was the rst to land on the moon of a planet other than Earth. There it discovered rain, rivers, lakes and seas. Cassini also found the rst evidence of extraterrestrial hydrothermal activity on the moon Enceladus, where it also observed erupting geysers. Its detailed observations of Saturn’s rings could help scientists understand how the planets in our solar system formed.
On the eve of the mission’s expiration, Newsweek spoke with Carolyn Porco—the leader of the imaging science team on the Cassini mission, who worked as an imaging scientist on the Voyager missions in the 1980s—about the stunning revelations and visual record of the historic ight.
What was it like when you were preparing for the Cassini mission?
I was just coming o the Voyager project, which was the best mission that’s ever been conducted. It had been such a rush to be part of such a historic voyage, like we were all just planetary explorers on Magellan’s ship. Then it came to an end, and we just wanted to do it again.
How did Cassini build on Voyager?
I was hoping we would answer many of the questions that we were left with after the Voyager encounters with Saturn. Voyager at each planet [it visited Jupiter, Saturn, Uranus and Neptune] was just a breathless rush, just a eeting glimpse, maybe a week or two of high-resolution views of what was in the planetary system. There were so many things we just got a few looks at, and we wondered, “What does that mean?”
There were some structures in the rings that hadn’t been predicted before Voyager got there, and they were spectacular to see. We spent the intervening 23 years trying to make sense of it on a theoretical basis. But really we knew [we needed] a closer look and more time there. Then there was Titan—voyager never got to see down to the surface of Titan because the capabilities of the camera, the imaging system, were exactly mismatched to the spectral absorbing characteristics of the atmosphere. We were anticipating
nally being able to explore the surface of Titan with Cassini. We knew how to alter our observing strategies so that we’d be able to see down to the surface.
What were your hopes for the Cassini mission? I was looking forward to the spectacular stu I knew we were going to get, because I knew what the capabilities of our camera system were compared to what we had carried on Voyager. I was expecting that we would come away with a far richer story about what the Saturn system was all about. My uno cial hope was that we would blow people away with the visual record of our travels around the Saturn system, like the ultimate interplanetary travelogue. I wanted to give people a sense of riding along with us. No one
“YOU’VE BEEN CHANGED BECAUSE YOU KNOW THAT HUMANITY JUST DID SOMETHING THAT HAD NEVER BEFORE BEEN DONE IN HUMAN HISTORY.”
really had ever done this. In the Voyager days, no one spent any time trying to gure out how to make the images artful or beautiful.
We also took sequences of moving phenomena so that we could, in a sense, turn our cameras into a video camera. We took images of the rings changing perspective when we were in orbit around Saturn. We made movies of the moons going around the planet, moons occulting other moons, shadows of the moons moving across the rings, changing cloud patterns, lightning strikes. We just turned it into a documentary. I think people really felt a sense of being there. It’s been a feast, an intellectual and visual feast.
What did the Cassini mission see in the rings of Saturn?
In the case of the moon Pan, we got to see that there were scallops on the edges of the Encke Gap. We didn’t expect that any disturbance created by a moon like Pan would go all the way— 360 degrees—around the ring. We thought it was just localized to the moon, and it turns out we were wrong.
Where the ring particles are shoved together because of perturbations by moons, the particles
+ Left, from top: NASA scientists, including Carl Sagan, discuss images from the Voyager 2 probe; prepping the Cassini spacecraft at Kennedy Space Center in 1997; Porco during a press tour in 2017.
After its launch at Cape Canaveral, Florida, in October 1997, Cassini traveled 2.2 billion miles to reach Saturn in June 2004.