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IRA FLATOW, host:

You're listening to TALK OF THE NATION/SCIENCE FRIDAY. I am Ira Flatow.

This week at the American Geophysical Union meeting, scientists released several new images of Saturn's moons, and those pictures help paint a new and unexpected picture of the ringed planet. They were taken by the Cassini spacecraft launched in 1997 and now is circling Saturn.

Joining me now is Bonnie Buratti. She is a co-investigator on the Cassini science team at NASA's Jet Propulsion Laboratory, JPL out there in Pasadena. She joins us by phone.

Welcome back to SCIENCE FRIDAY, Dr. Buratti.

Dr. BONNIE BURATTI (Jet Propulsion Laboratory, NASA): Hi, Ira, it's good to be here.

FLATOW: You sound very excited about this.

Dr. BURATTI: Yes. It is...

FLATOW: What's--excite us all. Why are you so excited?

Dr. BURATTI: Well, Enceladus, which is kind of the gem in the crown of the satellites of Saturn, really represents the most exciting scientific detective story that I've ever been involved in.

FLATOW: Really?

Dr. BURATTI: Yeah. Back in 1981, when the Voyager spacecraft flew by Enceladus, we pretty much immediately knew--I was a graduate student back then. I was just entering this field. We almost immediately realized that this satellite was unusual in some way. It was as bright as freshly fallen snow. It reflected virtually 100 percent of the solar radiation, the sunlight that fell on it. Now our moon, which we think is pretty bright, only reflects about 10 percent. So immediately we knew that there's probably some activity on this satellite.

FLATOW: Tell us why that--how you connect the dots on that.

Dr. BURATTI: OK. Well, the only thing we know of that is that bright is fresh ice. We also had a couple of other pieces of the detective story. There was this strange ring around Saturn. I mean, we all know that Saturn has these bright, beautiful large rings, but there's also this ring that extends out beyond the main ring system, called the E ring. It's kind of a gossamer, tenuous ring that you can hardly see, even in...

FLATOW: Oh, yeah.

Dr. BURATTI: ...the very strongest telescopes.

FLATOW: Right.

Dr. BURATTI: It seems that this ring was originating at Enceladus, because the thickest, brightest part of the ring was right at Enceladus. So we...

FLATOW: You mean, the ring was--you mean it's because of Enceladus that the ring existed?

Dr. BURATTI: Well, that's what we thought. Now we have proof.

FLATOW: Oh.

Dr. BURATTI: But back then, there was just a kind of circumstantial evidence that that was that part of the detective story.

FLATOW: Right.

Dr. BURATTI: But it wasn't until Cassini that we got the smoking--or maybe I should say the steaming gun, that Enceladus is the source of this ring.

FLATOW: Tell us why--well, you know, you paint a great picture. Keep filling in the details. Why do you say that? What have you seen that makes it the source of the ring?

Dr. BURATTI: OK. We first started getting suspicious back in March, March of this year, when the magnetometer on Cassini reported that it appeared that the magnetic field of Saturn kind of draped around Enceladus. And Michele Dougherty, who is the principal investigator, talked to the project about trying to go down very low, very close to Enceladus on our next encounter. This encounter in July 14th of this past year, and the plan was to go down about 500 kilometers from the surface. Michele asked to go down 200 kilometers or even less.

FLATOW: That's about--closer than our own moon to this planet.

Dr. BURATTI: Yeah, much, much closer.

FLATOW: Yeah. Yeah. Yeah.

Dr. BURATTI: It's really kind of flying over the rooftops almost of Enceladus.

FLATOW: Right. Right.

Dr. BURATTI: So the project--you know, all the scientists were very supportive, and it did take a lot of work to, you know, change a spacecraft trajectory, but people at JPL managed to do it, and we went down actually about 175 kilometers from Enceladus on July 14th. And the whole pieces--all the pieces of this forensic puzzle started falling together. The first kind of `gee whiz' `Oh, my God, something is really happening there' occurred when the composite infrared spectrometer noticed--measured this hot spot at the south pole of Enceladus. It was 20 degrees at least, Celsius, which is about 50 degrees Fahrenheit, brighter than it should be. In fact the south pole of Enceladus was the brightest part of the satellite--of the moon, whereas it should be the coldest.

FLATOW: Wow.

Dr. BURATTI: So it looks like there is something happening there.

FLATOW: Yeah.

Dr. BURATTI: And then the field and particles experiments started detecting all this ice and dust spewing out of the south pole. And another instrument saw fresh ice at these very strange features at the south pole; we call them tiger stripes. There were four--they're kind of just striations or linear features.

FLATOW: Right.

Dr. BURATTI: And there was very fresh ice at these unusual features. I think they're called linea(ph) in the geological terminology. But we didn't see the smoking gun--the steaming gun yet. What we decided to do on the Cassini project was try to get a long integration exposure, you know, take a photograph, an image of Enceladus with a very long integration--a long exposure time, just like you might do if you were trying to photograph fireflies at night.

FLATOW: Right.

Dr. BURATTI: You would turn up your--make your exposure time very long. Well, that's what we did. So at the end of last month, at the end of November, we turned the instruments at Enceladus and took a very long exposure and, lo and behold, we discovered active volcanoes on Enceladus.

FLATOW: You saw them spewing out?

Dr. BURATTI: Yes.

FLATOW: And what were they spewing out?

Dr. BURATTI: We're pretty sure it's water ice. That is the only thing that has been detected for sure so far. Now, you know, the interesting thing is--you know, it's been pretty hard to melt water ice...

FLATOW: Yeah.

Dr. BURATTI: ...out there, it's so cold.

FLATOW: Yeah.

Dr. BURATTI: And scientists thought that there had to be ammonia underneath to kind of act as an antifreeze to lower the melting temperature and allow this material to be spewed out. But the big puzzle is, we haven't found any ammonia. We only see the water ice. But we have shown for sure that this plume is the origin of the E ring. The E ring is being created by ice particles coming out of that plume.

FLATOW: Wow. if you go to our Web site at sciencefriday.com, we have a picture on the Web. It's really interesting.

So this is like--this is feeding the E ring.

Dr. BURATTI: Yes. We've proven that by showing that the spectrum or the color of that plume is identical or nearly identical to the color or spectrum of the E ring. It's not identical...

FLATOW: Yeah.

Dr. BURATTI: ...or similar to the spectrum of the surface of Enceladus.

FLATOW: And is this why Enceladus is so white, because you have new water ice coming out and freezing and...

Dr. BURATTI: Exactly.

FLATOW: ...keeping it white all the time?

Dr. BURATTI: Exactly. It's effectively snowing on Enceladus. I mean, even the areas of Enceladus that aren't active, you know, that have--they're heavily cratered and look like they're old, they are coated with these ice particles.

FLATOW: Wow.

Dr. BURATTI: It's kind of like a winter wonderland up there. Great scene.

FLATOW: Good seasonal story.

Dr. BURATTI: Exactly.

FLATOW: Well, this gets even more interesting because if it's hot enough to vaporize the water and bring it out of a volcano, it should be still warm beneath the ice then, right?

Dr. BURATTI: Yes. Yes. Yes. It's a puzzle. I mean, at this point, we are gathering the data. We have all the forensic evidence to show that there's an active plume and it's feeding the E ring, but we don't understand the mechanisms yet. It could be tidal heating. It could be heating that's caused by radioactive elements in the interior of Enceladus, things like uranium. Enceladus is denser than most of the other satellites, which means there could be more rock, which tend to contain radioactive elements like uranium. So that might be part of it, but we think tidal heating is also helping the process.

FLATOW: Well, whenever you have water and heat together, you have speculation about--go ahead, fill in the sentence--life.

Dr. BURATTI: Yes, exactly. Exactly. Yes. That, of course, is in many respects one of the most exciting possibilities here. There's been a lot of talk about life on Europa.

FLATOW: Right. Right.

Dr. BURATTI: I mean, you mentioned...

FLATOW: Jupiter's moons. Yeah.

Dr. BURATTI: Yeah. You mentioned earlier in the program that, you know, when we talk about interesting moons, we usually talk about the moons of Jupiter, because Io, which is, you know, another volcanic world--I mean, this is the third time we've discovered volcanoes on moons in the solar system. There's Io, and there's also Triton, the giant moon of Neptune.

FLATOW: Right.

Dr. BURATTI: But Europa, which is the second major moon out from Jupiter, there's been a lot of speculation about life on Europa because it does have a liquid ocean underneath the surface, and there's also the possibility on Enceladus. You know, the problem is, you know, there has to be sunlight, too. Well, how does the sunlight get down there to the liquid part of the ocean, if there is an ocean underneath? You know, there are--it's interesting to speculate, but we don't have any proof of that. It's--all the elements are there, but, you know, we'd have to look a lot closer to talk about life.

FLATOW: Yeah. I was thinking--I was reading just in a totally different story the other day about--I think it was an ice core sample taken from Greenland where they had found, I think it was, methane way down there, and they couldn't figure out how it could have happened down there. And they thought maybe there were these archibacteria. Possibly that kind of very primitive, very hearty life-form?

Dr. BURATTI: It is quite possible. In fact, it's interesting that you bring up Antarctica, because a lot of the studies to bring robotic exploration to Europa, the large satellite of Jupiter, to look for life is being tested down there..

FLATOW: Yeah.

Dr. BURATTI: ...at places like Lake Vostok in Antarctica that is a subsurface ocean and looking for things like these archibacteria that you're talking about.

FLATOW: Yeah, I think this--I may have misspoken. I think this is in Greenland where the core...

Dr. BURATTI: Was it Greenland? Yeah. OK.

FLATOW: But similar to Antarctica, very similar kind of rocky stuff. So that's why you're so excited about this. It's hard to hear a scientist say, `This is the most exciting thing I've ever worked on.'

Dr. BURATTI: Oh, this is for sure. The plumes on Enceladus are the greatest thing I've ever been involved in.

FLATOW: So then you finally have another planet where--you know, that matches Jupiter in exciting moons around it. Are there any other--there are--What?--how many dozen moons around Saturn now. They keep getting more and more.

Dr. BURATTI: You know, I've lost count. I think it's up to 43, but don't quote me. It's in the 40s someplace.

FLATOW: Are they buried in the rings, or are they just not seeable usually?

Dr. BURATTI: There are some that are within the rings that scoop out...

FLATOW: Right.

Dr. BURATTI: ...ring particles and cause the gaps. There's some that shepherd the rings. But the reason we keep adding to the numbers is that there are these captured satellites, outer satellites of Saturn, small rocks, that keep being discovered, mainly from the ground. The outer ones are discovered from ground.

FLATOW: Right.

Dr. BURATTI: But the Cassini spacecraft, of course, has discovered a few in the inner system.

FLATOW: 1 (800) 989-8255. Let's go to Phil in Syracuse.

Hi, Phil.

PHIL (Caller): Hey, hello there. Let's see. OK, I've got a question about future missions to Saturn, and the connection I'm going after is funding. And just yesterday I was reading on the Internet that the new manned program to go back to the moon and Mars--the funding for that appears to be a little bit less next year than it hoped, and Administrator Griffin is talking about freezing the funding for space science, which is missions to Saturn and the moons of Saturn, such as Titan. And I know it's been a concern that people have mentioned earlier that this new program to return to the moon would start going after the funds for the unmanned programs. And it does appear that that might be happening. And so my question is, what are these future missions to Saturn and its moons, and what is this concern if this new manned program to go back to the moon starts affecting the unmanned program?

FLATOW: Dr. Buratti?

Dr. BURATTI: Well, I'd like to be really--yeah, I'd like to be really optimistic about that. I mean, you know, I'm old enough that I remember the Apollo program, and that was a great time for scientific exploration of the solar system. There was kind of a coattail effect where people were so excited about sending people to the moon and possibly later to Mars that it kind of raised all boats, so to speak, that we all benefited from that. And I'm hoping that something like that might happen, that we'll just get so excited about exploring space that it's going to just help us all. I mean, clearly going back to Enceladus and also Titan, which is another interesting moon around Saturn, a giant satellite that has many similarities to the Earth. I'm just hoping that it just, you know, might raise all our boats and increase funding for space science.

FLATOW: Thanks, Phil.

PHIL: OK. You're welcome.

FLATOW: Bye-bye.

1 (800) 989-8255 is our number. We're talking about the Cassini mission and Saturn with Bonnie Buratti of JPL on TALK OF THE NATION/SCIENCE FRIDAY from NPR News.

Of course Cassini--you mentioned going back to Voyager--is of that kind of class of sat--the last one of its kind, the big, giant, do-everything kind of probe, isn't it?

Dr. BURATTI: Yes, it is. It's kind of the Cadillac of the missions. It can do so much. We have just almost an embarrassment of riches when it comes to the data. It's just--we can't keep on top of it. It is the last mission that is of that is of that status or scope. But, you know, there is for example the New Horizons mission that's going to be launched hopefully in January to Pluto. That's also a very exciting mission and that is a fairly sophisticated spacecraft. And, you know, we're already talking about follow-on missions to Titan and Enceladus and possibly Europa. So we're really at the drawing board working very hard.

FLATOW: What about missions that are past the drawing board? Are there ones that are in the works to the moons of Jupiter or Saturn?

Dr. BURATTI: There haven't been any that have been approved yet.

FLATOW: And I think that's what the caller was worrying about.

Dr. BURATTI: Yeah. I mean, right now it is kind of, you know, a single pot that we're all taking from. So, you know, it would be natural to think that if we're going back to the moon and going to Mars, it might, you know, cause outer planet studies to suffer, but I think we just have to advocate and push for continuing these exciting discoveries.

FLATOW: You know, there's this push to bring in private corporations, you know, to do orbital missions, people--you know, the Burt Rutans and people like that. Could we not bring in private people to get financed, you know, missions to the planets?

Dr. BURATTI: You know, I'm not a businessperson, but my first reaction would be, hmm, I'm not sure this stuff is profitable. We're doing this to advance knowledge...

FLATOW: You know, universities and things like that that do basic research and could--a consortium, you know, just because it would--I agree with you, it's a shame not to have more missions to these planets where you're finally finding the exciting stuff you've been waiting for, your most satisfying mission so far.

Dr. BURATTI: Absolutely. Yeah, there hasn't been anything else like Cassini and, you know, I really hope that the taxpayers will support continued government spending of these programs that really, you know, keep our nation ahead in terms of just cultural and scientific activities.

FLATOW: Any of the other moons of Saturn that have been looked at, you know, that have been sending back data lately that seem to shed some new light on something?

Dr. BURATTI: Yeah, they've all got an interesting story. One of my other favorite objects is Hyperion. It turns out that this satellite--it's the only satellite that we know of in the solar system that rotates chaotically. It can't even decide, you know, what it's--you know, how it's spinning. It seems to have been the victim of a violent collision in the past. And the most fascinating thing we found out is that it has a density less than that of water. I mean, we all know, we all learned in school at some point that, you know, Saturn would float on water. But this object, Hyperion, is even lighter than that. It only has a density of about 60 percent that of water. And we're trying to figure out why. It seems to be almost a rubble pile. It had a very violent past. Maybe it was completely broken up and just kind of came together again.

FLATOW: Wow. You know, I think, if there aren't people listening to you who are not excited and want to go into this field, listening to just your enthusiasm is refreshing to all of us. I want to thank you for taking time to talk with us. Do you have any wish list that you would love to be able to, you know, do and go on another mission? What thing would you like to do if I could give you a blank check?

Dr. BURATTI: I think I would like to land on Titan and move around. I mean, we did land on Titan with the Huygens experiment...

FLATOW: Right.

Dr. BURATTI: But I'd like to set up a weather station on Titan and go back to Enceladus. But, you know, Titan is more like the Earth, you know.

FLATOW: Right.

Dr. BURATTI: It has--we also think it has volcanoes and prebiotic conditions. But, yeah, I'd like a weather station.

FLATOW: All right.

Dr. BURATTI: Observation post on Titan.

FLATOW: All right. Well, I'm taking up a collection.

Dr. BURATTI: Thank you.

FLATOW: Thank you. Bonnie Buratti, who is a co-investigator on the Cassini science team at NASA's Jet Propulsion Laboratory in Pasadena, thank you for taking time to be with us.

We're going to take a brief break, and when we come back, we're going to talk about--stay with astronomy, talk about the meteor shower that's coming up next week and what else you can see in the night sky over this winter. So stay with us. We'll be right back.

I'm Ira Flatow. This is TALK OF THE NATION/SCIENCE FRIDAY from NPR News.

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