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So long, Cassini — it’s been a ride

May 13, 2017

As it nears mission’s end, the Cassini spacecraft has begun a delicate space dance.

Slipping through Saturn’s rings for the first time, the space probe now is sending back some of the most stunning, detailed visual images of Saturn and its rings. Four months from now, the probe will go silent when engineers plunge the craft into the planet’s atmosphere and destroy it. It will be the end of a 20-year space mission.

John Moore-Weiss, a graduate of John Marshall High School and Carleton College, said he will feel sadness but also a sense of pride at all that Cassini has accomplished during its 20-year mission.

As a scientist who has worked on the project, both as a post-doctoral student and a contractor, Moore-Weiss says Cassini’s impact will extend for generations. (Moore-Weiss is the son of retired longtime PB reporter John Weiss).

“There are going to be graduate students, well after the spacecraft is gone, that are going to be using this data,” Moore-Weiss said.

Since settling in Saturn’s orbit in 2004, Cassini has almost exclusively flown outside the planet’s main rings. But on April 26, the space probe began threading the gap through the innermost ring and the planet. It will be one of 22 planned orbits before it begins its death spiral.

Scientists long have had specific questions they hoped Cassini might answer, Moore-Weiss said. But planning a space exploration means preparing for things no one anticipated would be discovered. So the craft was designed like a “Swiss army knife,” built to do almost everything “decently” but not any one thing perfectly.

Heady days

There was a sense of elation when engineers were first able to turn the craft’s cameras on the rings for the first time and look at them up close in a way no other probe had been able to do, he said.

“I hate to call them heady days, but they kind of were. It just seemed like every week, we were like, ‘Oh, my god, there’s this cool new thing we discovered,’” Moore-Weiss said.

But it’s Saturn’s moons that made scientists’ hearts skip a beat with excitement. That is not to dis Saturn and the other giant planets in our solar system. Moore-Weiss calls them “basically large atmospheres.” Yet, it’s the moons that tend to fascinate.

“Jupiter itself is a very interesting body,” Moore-Weiss cites as an example similar to Saturn. “But it’s got those four giant moons, three of which have water oceans. And one is volcanically active. That’s just hard to beat.”

And Saturn’s’ moons, Titan and Enceladus, are thought to be the most likely places to find life.

“Titan, we thought, was a place to go looking for stuff like that,” Moore-Weiss said. “I mean, it’s not going to look like terrestrial life most likely.”

Bigger than earth’s moon, Titan has an atmosphere and clouds. It has a surface shaped by rivers and lakes of liquid ethane and methane. Titan is also fantastically cold, about minus-290 degrees Fahrenheit.

Water jets

And then there is Enceladus.

“We knew there was something weird about Enceladus, because it is the most reflective body in the solar system,” Moore-Weiss said. “It’s basically as shiny as brand-new snow.”

In 2005, Cassini snapped pictures of Enceladus backlit by the sun that showed water jets flowing out of the south pole. Moore-Weiss and other scientists argued about the meaning of those jets. Enceladus is “really, really cold,” but the plume of water flying off into space suggested a warmer place closer to freezing.

“Lately, the consensus seems to be coming down on liquid water, even a global ocean under the ice, of water everywhere,” he said. “The south pole is like cracks letting the stuff out.”

“With its global ocean and internal heat, Enceladus has become a promising lead in our search for worlds where life could exist,” a National Aeronautics and Space Administration website stated.

Cassini’s mission was only meant to last four years, but it ended up spending 13 years around Saturn as NASA extended it to answer new questions.

Moore-Weiss might be a scientist, but he’s not without feelings. Given the yeoman’s work Cassini has performed, he says it’s sad it has to be destroyed. He would rather see it parked somewhere.

“Somebody pointed out we could actually soft land it on one of the very small moons,” he said. “In 50 or 100 years, my grandkids could arrange to have someone go out and grab the spacecraft. We could bring it back and put it in the Smithsonian.”