MARY LOUISE KELLY, HOST:
NASA's Cassini mission to Saturn is over. This is a probe, the size of a school bus, which has been orbiting the ringed planet for 13 years. But this morning, it plunged into Saturn's atmosphere and disintegrated. NPR's Joe Palca is at NASA's Jet Propulsion Laboratory in Pasadena, Calif., which is where the control room for Cassini is located.
Good morning, Joe.
JOE PALCA, BYLINE: Good morning, Mary Louise.
KELLY: What's the mood there? You're hanging with all the scientists. Is it despair, jubilation - what's it like?
PALCA: You know, it's kind of interesting. There are - we saw packages of tissues on chairs just in case there was a little chin quivering as it went. I don't think people felt bad about shedding a tear. You know, a lot of them have spent their entire careers working on this mission, and it's gone. So you know, they can be forgiven, I'm sure.
But there's also a lot of enthusiasm because this mission provided just a ton of interesting data that scientists are only still sifting through. You know, some of this data has been collected over 13 years, and they're going to have to sort of lay it out in a time sequence so they can see what kinds of changes have occurred over, essentially, half a Saturnian year.
KELLY: Well, let me back you up. We said it plunged into Saturn's atmosphere and disintegrated. We should note this was on purpose. NASA...
PALCA: Yes. Not - wasn't an accident.
KELLY: NASA decided to end it. How come if it was producing useful stuff?
PALCA: Well, there was an issue of the fuel, which was almost gone. And NASA...
KELLY: Oh, well, there's that.
KELLY: You're out of gas, OK.
PALCA: But it can stay in orbit for, you know, for quite a while without fuel, except for - the concern was that there are a lot of moons in Saturn that can give the spacecraft a little nudge. And it's possible that in some future orbit, it could bang into one of these moons and hit it and crash. Now, that's not the world's worst thing, except for the possibility that there's some hardy microbe that hitched a ride to Saturn on the spacecraft. And the last thing NASA wants to do is to contaminate a moon that might possibly harbor some Saturnian life or some moonar (ph) - moon life with Earth life. So they thought, well, best to just have it disintegrate into Saturn.
KELLY: Incredible. You're talking about a microbe that might have hitched its way all the way from Earth...
PALCA: Yeah. Isn't that something? They can...
KELLY: ...And made its way through space?
PALCA: Yep, they think that's a possibility - that they can last in a sporelike condition and then reanimate.
KELLY: Was Cassini sending back pictures right up until the final moment?
PALCA: No. The pictures kind of wrapped up yesterday or day before. The very last part of the mission, the spacecraft was pointed so that its main antenna was pointed back toward Earth. And it was actually sending a signal from some of the instruments that were designed to measure the atmosphere of Saturn.
But it was kind of interesting. At the end, you could see that radio signal. It appeared as a line on a chart - or on a graph, a display. And then after, it was there, and it was there, and it was there. And then it was gone, and the mission was over.
KELLY: And what else have scientists learned? What's going to be the takeaway from Cassini?
PALCA: Well, as I say, there's still a lot of chewing on the data to be done. I think the most interesting is a better understanding of the rings, a better understanding of the magnetic field and a really amazing appreciation for how interesting some of the moons are, especially Titan and Enceladus, both of which scientists think might, might, might have the conditions that could harbor life. And so I think they're just really itching to get back after all the things they've learned from Cassini.
KELLY: Fascinating stuff. Thank you, Joe.
PALCA: You're welcome.
KELLY: That's NPR's Joe Palca updating us on the end of Cassini. He's speaking to us from NASA's Jet Propulsion Laboratory in Pasadena, Calif.
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