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JPL podcast: Water Evidence On Saturn's Moon Enceladus

Mar. 9, 2006
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Narrator: Big water news from a tiny moon of Saturn.
I'm Jane Platt and you're listening to a podcast from JPL -- NASA's Jet Propulsion Laboratory in Pasadena, Calif. We have some very exciting news from the Cassini mission about one of Saturn's moons Enceladus. We have a couple of guests today. First, we're going to hear from Dr. Carolyn Porco, imaging team leader for the Cassini mission. She's with the Space Science Institute in Boulder, Colorado. Carolyn, why don't you go ahead and tell us what you've found.

Porco:We had pictures dated back to January of last year, and then we had some more in February, and then we got some stunners in November which show these jets coming off the south pole of Enceladus, and we've been looking at these and studying them, and it seems, as far as we can tell, that these are geysers that are erupting out of pockets of liquid water under the subsurface of Enceladus. And this is just one of those smashing, surprising discoveries that we've just made and we're thrilled about it.

Narrator: Wow, and it's always big news when you find water anywhere in the solar system, correct?

Porco:
Uh, yeah, and I want to be a little bit clear here, we haven't found water, per se, we've found evidence of water, and our best models, right now, are those that suggest that there's pockets of liquid water under the surface, and what we're seeing in these jets are like the equivalent of Old Faithful, in Yellowstone, they're geysers that are erupting out of pockets of water. It doesn't seem to make sense that they are anything else, so we've, in some sense, almost reluctantly been driven to this conclusion because any other possibility just doesn't make as much sense as a geyser.

Narrator:
OK, and the geyser has to be driven by something, correct?

Porco:
You have to, of course, have heat and energy in order to keep the ice on Enceladus warm enough to melt, so that implies temperatures at least as warm as 0 degrees Celsius, or 32 degrees Fahrenheit, and that is what's so shocking about this, that there are temperatures that high on a body at the distance of Saturn. But that is the undeniable fact, we are seeing a warm south pole, even other instruments on the Cassini orbiter have detected warmth coming out of the south pole. So, together the warmth and the geysers, it's just all pointing in this direction, it's almost an unavoidable conclusion.

Narrator:
This raises the obvious question then if you have what you think is water and you have what you think is a heat source, well, what do we think about, not we, what do you experts think about the potential for possible life on Enceladus?

Porco:
Well, what you need for life as we know it, and that's always the disclaimer here, it's life as we know it here on the Earth, requires water. And it requires liquid water, and of course it requires the chemical ingredients from which to develop organic materials. Well, just about anywhere you look in the solar system these days, you can find organic materials. We find simple carbon-hydrogen molecules, methane for example, associated with the fractures in the south pole from which these geysers are erupting. So, there's organic materials, there's liquid water, there's a hydrological cycle, with water flowing underneath and then erupting out to the surface. So, it appears we have all the ingredients that all the experts have claimed for a long time now, you would need to have environments suitable for living organisms. And so, that's what we think we have here. We have found another environment in our solar system, in a very surprising place, that could host living organisms. Now, of course, we'll never know until we go there, but it's a very, very, very exciting possibility. It's really broadened the diversity of those environments that we can expect to see conditions suitable for life.

Narrator:
You say it was surprising to find this on Enceladus. Why is that?

Porco:
Because it's so small. Enceladus is no bigger than England. It's a tiny little place. It's only about 300 miles across. So that makes it also no bigger than let's say the state of Arizona. We wouldn't expect a body this small, before Cassini arrived there, to have enough rock, which means another material that can give rise to radioactivity to heat anything. We wouldn't have expected that process to warm the interior enough to heat liquid water, and that's probably not the process that's doing it. It's undoubtedly something else, and that something else, it seems it has to do with flexure. Enceladus is being flexed, like one might flex a rubber band or a paper clip to make it warm, it seems to be flexed. And together with the rock and radioactivity heating the interior, that seems to be enough to give us warm temperatures, surprisingly warm temperatures and liquid water. We're still at a loss to know, though, how even flexing Enceladus could make it warm enough. But, ya' know, like one of my team members has said, even if we can't figure out how Enceladus can do it, Enceladus has obviously done it. So, that is our puzzle, and our mystery to crack.

Narrator:
Yeh, I was going to say there are a few places in the solar system that are of great interest, Europa of course around Jupiter. Rattle off for me the places that are interesting that Enceladus is probably going to join the list with.

Porco:
As far as a body that has present day activity on it, it joins, of course, the Earth, it joins Io, the Jovian moon that is highly volcanic and lots of plumes, but they're volcanic plumes, not geysers. And then, believe it or not, Triton, which is a major planet, although a small one of Neptune.

Narrator:
A major moon.

Porco:
I'm sorry, major moon, which also has geysers there, but they're driven by a completely different process, not one with liquid anything. But, nonetheless, nitrogen geysers on Triton. And so now we have Enceladus with its beautiful display of jets and plumes, like fountains coming off the south pole. So in terms of geologic activity, it joins a handful of bodies, but as far as a place where we might have liquid water, which of course is the key, it's like the holy grail of studies of life in the universe, again, life as we know it, then it joins Europa, it joins possibly the subsurface of Mars, it joins, of course, the Earth, and I think that's it.

Narrator:
That's a short list. Porco: And perhaps, some of the other moons of Jupiter, which may also have deep but, may also have deep oceans.

Narrator:
You mention fountains and things erupting. If you were able to, you've only, I don't mean only, but you've been able to see this from the Cassini spacecraft above Enceladus, but if you were able to stand on Enceladus, do you know what you might be seeing? Porco: Oh, that's a very interesting question and really a delight to think about, isn't it?

Narrator:
I mean would it be like a Yellowstone National Park where you go up to a certain area at a certain time and you know Old Faithful's going to erupt and you watch it? It could look like it? Porco: It could look like that close to the surface. But mind you, this plume in our pictures extends at least 430 kilometers above the surface of Enceladus, that's almost as big as Enceladus is itself. So it's literally a gargantuan plume, you can just look at our images to see that.

Narrator:
Thank you so much for joining us today to talk about this very exciting news.

Porco:
Oh, my pleasure, believe me. Laughter

Narrator:
All right, we've been talking today with Dr. Carolyn Porco, she's the Cassini imaging team leader, and she's with the Space Science Institute in Boulder, Colorado. We are joined now by one of her colleagues on the Cassini imaging team, Dr. Torrence Johnson, who's right here with us at JPL. Torrence, in the big picture, what does it mean now that you and your colleagues have found evidence of liquid water on Saturn's moon Enceladus? Johnson: It certainly means it's a place that bears a lot of study in the future and we'll be trying to observe it more with the Cassini spacecraft. We're already altering our plans for observations in the future to see if we can get more data on Enceladus, and I wouldn't be at all surprised if this didn't become another major target for exploration in the future to go back and see what it might mean for biology and whether these types of systems on a small, sort of a geyser field on a small icy moon might be, in fact, a good place to look for possible life.

Narrator:
So you didn't think there could be liquid water on a moon so small, and there are a lot of moons around Saturn alone, some of them I'm assuming pretty small. So does this sort of open a door and raise the possibility that there could be water and potentially other components necessary for life in more environments than you even dreamed? Johnson: In a way, these discoveries we've been making over the last few years sort of open up scientists' ideas of where a habitable zone is. And if we're finding more of these types of places and the energy sources to have liquid water in these what we had previously regarded as inhospitable environments, it could well be that icy moons around other stars, around planets of other stars, might be the most common places where you would have the right ingredients for life, which is sort of a turnaround from some of the previous thinking.

Narrator:
We've been talking with Dr. Torrence Johnson of JPL. He's on the Cassini imaging team. We also spoke with the team leader, Dr. Carolyn Porco of the Space Science Institute in Boulder, Colorado. For more information on Cassini's studies of Saturn and its moons, including Enceladus, go to www.nasa.gov/cassini. Thanks for joining us for this podcast from NASA's Jet Propulsion Laboratory.

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