Planetary Radio: Space Exploration, Astronomy and Science - The Volcanoes of Io

Episode Date: February 24, 2003

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This is Planetary Radio. Hi again everyone, I'm Matt Kaplan. What a hot show we have for you this week. Forget about Vesuvius and the big island of Hawaii. There's only one place in the solar system where you'll find over 100 active volcanoes. And no one knows that lava-lathered sphere better than our guest. Dr. Rosalie Lopez joins us to talk about Jupiter's moon Io, along with a few of Earth's own hot spots, many of which she has visited.

Later, Bruce Betts will provide his entertaining review of Earth's own hot spots, many of which she has visited. Later, Bruce Betts will provide his entertaining review of What's Up. But let's get started with this volcanic intro from Emily. That's Planetary Radio for you, simply erupting with information. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, what is the biggest active volcano in the solar system? Nearly every rocky body in the solar system shows evidence of a volcanic past, but there are few planets that we know have active volcanoes. Earth, of course, does have active volcanoes.

At 120 kilometers wide, the biggest active volcano on Earth is Mauna Loa in Hawaii, which last erupted in 1984. The volcano is so massive that it bends the Earth's crust downward beneath it, creating an 8-kilometer-deep dent in the Earth. If you measure the volcano's height from the bottom of this hole, Mauna Loa's summit lies 17 kilometers, or 56,000 feet above its base. Hawaiian volcanoes are fed by a heat source that lies very deep within the earth, possibly at the boundary between the earth's solid mantle and its molten core. The earth's heat comes from three sources – primordial heat left over from its formation 4.5 billion years ago, heat from the decay of radioactive elements, and heat released as the molten

outer core of the Earth slowly freezes onto the solid inner core. Scientists once thought that only big, rocky bodies like the Earth and Venus, and maybe Mars, could still be volcanically active. But the biggest active volcanoes in the solar system are not on any of these planets. To find out where the prize volcanoes are located, stay tuned to Planetary Radio. Dr. Rosalie Lopez joins us on Planetary Radio. Rosalie, first of all, thanks for being here. You're welcome. Tell us why, in roughly 1979, when Voyager made its flyby of the planet Jupiter,

this odd moon Io came to be called the Pizza Moon. Well, when Voyager first flew by Io, the scientists in the imaging team who were looking at the images of Io were very puzzled. Io seemed just about the strangest object they had ever seen in the solar system. Io is a moon about the size of our Earth's moon, but its colors are very strange, lots of oranges and yellows and blacks. And one of the scientists said, it looks like a pepperoni pizza. And it stuck.

And it stuck. It looks like a pepperoni pizza. And it stuck. And it stuck. And one of the surprises was that Io didn't have any impact craters. Now, if you look at the moons of the solar system, because there are meteorites and asteroids around in the solar system peppered with craters, and if there are not any craters there, it's because something has obliterated them.

Some other process has wiped out those craters. So at first, the mystery was what had caused those craters to disappear that should have been there. And they quickly came to realize that there were active volcanoes on this little moon, lots of them. Yes. In fact, the discovery was made by Linda Morabito, who was a member of the navigation team, and she looked at one of the images of Io taken for navigation purposes because we use the cameras on the spacecraft also to help navigation. And she noticed an umbrella-shaped plume on the side of Io and thought this may be an

erupting volcano. When one of the other instruments on that spacecraft, looking at infrared wavelengths, detected some heat that coincided with one of the plumes, it became quite clear that active volcanoes were around, and they found about a dozen plumes and about a dozen hot spots, as they called them, the active volcanoes, and it became clear that this moon had active volcanism. And this is so important because Io is the first place outside Earth where we have actually seen active volcanoes. And I think, you know, you said all the colors of this odd-looking moon.

I think it's beautiful. I think it's quite a place. And, of course, it's changing all the time. Yes, Io is a real cartographer's nightmare. People start making maps of Io, and then it changes. people start making maps of Io and then it changes. And it even changed during the two Voyager flybys that were only four months apart. Particularly the deposit from one of Io's largest plumes called Pele actually changed in shape. It went from being heart-shaped to circular.

So there were noticeable changes even in four months. So we had this tantalizing couple of looks at this amazing little moon. And then the Voyager spacecraft flew on. And a lot of years went by as folks like you, scientists, you in particular as a volcanologist, must have been going crazy waiting for the next visit, which, of course, was Galileo. Yes, and the Galileo launch was delayed, and the Galileo mission only finally got off the ground in 1989. And it had a long flyby around the solar system to get to Jupiter. It did gravity assists at Venus and at Earth.

And we finally got to Jupiter in 1995, got into orbit around Jupiter, and then started looking at Io in the middle of 1996. But it was worth the wait. There were a number of surprises. Of course, there had been changes, as we had expected, in the years between Voyager and Galileo. Io had, in fact, been observed from Earth, from Earth-based telescopes, and the most violent eruptions could be detected from Earth at infrared wavelengths. So we knew that a lot of activity was still going on,

and particularly from a volcano called Loki. But in fact, where we saw some big surface changes in some places, Loki looked pretty much the same as it had during the time of Voyager. So there were places with a lot of changes on the surface and places where there had been a lot of volcanic activity, but the activity was confined within a big volcanic crater that we call a caldera. So it was also surprising that some places where we expected big changes, we didn't find them. I love these names, by the way, Pele and Loki, and another one that's going to come up later in our conversation, Tvashtar.

Am I pronouncing it correctly? Yes, yes. Those are all after gods and heroes related to fire and volcanoes and thunder. In fact, I suggested a name to the International Astronomical Union. In fact, a couple of names, Tupan and Monan, and they were accepted as names of volcanoes.

And these names come from Brazilian native mythology from my native country. And so I was very pleased that those were accepted. You must be very proud. I would be if I had a volcano out there near Jupiter that I had named. Let's talk about what else Galileo learned. We have these spectacular images, which can be seen on the Planetary Society website and also at the JPL site where you work. But there were other instruments on Galileo, some of which created images, some didn't. One that you worked on was this instrument that worked

in the infrared rather than the visible range of light or light wavelengths? Yes, I worked with NIMS, which is the Near Infrared Mapping Spectrometer, and it turned out to be extremely exciting because in the infrared wavelengths, you can detect heat from the volcanoes. So we were able to discover many new volcanoes on Io, active volcanoes. And that was pretty exciting for me. I was always the first person to analyze those infrared images and to detect all those volcanoes. I think I detected over 40 new ones.

After a while, I stopped counting. But, you know, just to say, oh, that's another active volcano, another active volcano. It was really very exciting. And we worked very well with the imaging team because it was a lot harder for them to tell if something was actually active or not. They could only tell it if they had observed Io in eclipse from Jupiter when it was totally dark. And then at one micron, using a one micron filter, they could detect high temperatures. But we could detect lower temperatures, and we could detect heat even when Io was in reflected sunlight. And one micron being a reference to filtering the wavelengths of visible light that they could make out.

That's right, yes. So really the instruments, even though it does sometimes seem like the visible light images get all the attention, all of the instruments on the spacecraft work together to paint the picture. Yes, and in fact, you know, one of the eye of close flybys, it was quite interesting, of the eye of close flybys. It was quite interesting. The imaging team detected a plume, and they expected it to be coming from a volcano called Chvasta,

which was, you know, it's a very active volcano, and, you know, we had detected a major eruption from there. And then analyzing the images and doing the geometry of the plume, they figured out it didn't quite fit the location of Trivastar, but it was, you know, fairly close. And they were making some tentative identifications when I received an infrared image, a new one, it was downlinked. And I saw this great thermal emission in the infrared from a new volcano, at least one that we had never seen to be active before. And so I told my colleagues on the imaging team, I know where your plume's coming from.

We're going to take a break. When we come back, we want to talk more about Io, but maybe also talk about volcanoes in general, because while you haven't been to Io, you've done the next best thing with Io, but you have been to a lot of volcanoes and studied them here on Earth, and you're even writing a book about them, intended for the layperson. So if we can, we'll continue that conversation in just a moment. My guest is Dr. Rosalie Lopez, and Planetary Radio will continue right after this.

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at our exciting and informative website, PlanetarySociety.org. The Planetary Society. Exploring new worlds. Matt Kaplan back with our guest this week, Dr. Rosalie Lopez of JPL, planetary scientist, volcanologist. And we were talking about Io.

Before we leave the topic of that hot topic of that hot little moon, do we now understand why Io is so beautiful, why it has all those amazing colors you talked about a few minutes ago? We think there is a lot of sulfur on Io, and that's what it gives these colors, the oranges and the reds. There are different forms of sulfur. We also understand a lot more about Io now than we did at the time of Voyager. We know that there are many more active volcanoes than we knew about from Voyager. We knew of about a dozen after the Voyager flybys,

and now we know there are more than 120. So Io is really literally covered with active volcanoes. And we also seen something very interesting on Io. We detected lavas hotter than any lava that we see on Earth today. detected lavas are hotter than any lava that we see on Earth today. And these lavas are similar, we think, to lavas we call Comatheites, that geologists call Comatheites. They are very ancient, primitive lavas on Earth.

So in a way, studying Io is like looking at the Earth billions of years ago, and that was unexpected and very interesting for us. Fascinating. And I think that we also think we understand now why this moon turns out to be so unexpectedly active. Yes. Io is located between Jupiter, which has, of course, a huge gravitational attraction, being a very large planet, and other large moons that we call the Galilean satellites, Io, Europa, Ganymede, and Callisto are called Galilean satellites because they

were discovered by Galileo with his telescope. And Io is in a very peculiar orbit. So it's being pulled on one side by Jupiter and on the other side by the other moons. You can imagine it in a simple way as a tug of war. And that generates tides on the surface, actually in the crust, which would be like ocean tides, except that the whole crust is suffering them. And that generates friction and heat, and that's what keeps the interior molten. generates friction and heat, and that's what keeps the interior molten.

If it wasn't for that peculiar orbit, Io would have cooled a long time ago, very much like our own Earth's moon. Well, I guess we should be glad it hasn't, because it certainly would be less interesting. Right on. We mentioned, of course, you can't go to Io, you've done the next best thing, but you have been to many volcanoes here on Earth. Yes, I started studying volcanoes in 1979, and I have been to many of the Earth's volcanoes.

And I particularly like active volcanoes. So I did a lot of my Ph.D. work on Mount Etna in Sicily. I worked at Vesuvius, and I've been to Hawaii, and a bunch of times in Iceland, and Martinique, and Montserrat, and a number of other volcanoes. And I think active volcanoes are just the most fascinating places on Earth. Well, you're not alone. Obviously, a lot of the public feels that way. And because of that, before we're done, we'll have to mention the book that you're working on. But I wonder, and you started to talk about this, you talked about those very hot forms of lava that seem to still be active in the volcanoes on Io, and how this appears to be much like these

ancient lava beds on Earth. Are we learning more? I mean, what has Io told us about volcanic activity here at home? Well, when we look at volcanic activity on a different planet, the nice thing is that we can see how volcanic eruptions work under very different environments. For example, here on Earth, you can go to one volcano and then another volcano that has a different composition of the lava, You can go to one volcano and then another volcano that has a different composition of the lava. But you can't change things like the gravity or the thickness of the crust. And you can't change the composition of the lava that much. Some of these really hot lavas on Earth, you know, have been dead for a long, long time.

So when we look at volcanoes on Earth, we try to figure out the physics of volcanic eruptions. And it's actually very useful to be able to look at eruptions on another planet and test out what we are seeing on Earth and test out some of our theories, how lava flows evolve, how volcanic plumes evolve. And Io is certainly an extreme environment. Also, it has no atmosphere. So there is, you know, it's almost a different discipline of actually looking, for example, at explosive volcanism in a vacuum. You know, it's very, very different.

So we call it a natural laboratory. You know, it's like going, you's like setting up different conditions somewhere else. So that makes it quite fascinating. Let's talk more about that fascination that people have for volcanoes and how that has led you to start writing a book, which you said I guess you're hoping is going to come out in the fall. a book, which you said, I guess you're hoping is going to come out in the fall. Yes, I have given many lectures in the past about Earth's volcanoes, and a lot of people ask me, oh, I'd love to see a volcanic eruption, and volcanic eruptions are really fascinating, and is it dangerous to go to an active volcano?

And I realized that although there are a lot of books about volcanoes, there were no books about visiting volcanoes. So that's what I did. I wrote a book called The Volcano Adventure Guide, which I hope is going to be out in the fall. It's being produced by Cambridge University Press. And it tells people about some of the Earth's most fascinating volcanoes and how to go to them and which eruptions, which type of eruptions you can watch relatively close and in safety and which eruptions you should really get away from. All right.

Well, we may have to have you back and learn a little bit more about that book when it comes out in the fall. Before we finish, we've only got a minute or two left. Tell us a little bit about what you're up to now, since Galileo has pretty well finished its life, although it's got a spectacular ending coming up. Yes, we have finished collecting data observations with Galileo, and Galileo is going to plunge into Jupiter for a fiery death. And on purpose. On purpose, in September of this year. And the reason we're doing that,

it's because if we just left Galileo in orbit around Jupiter, there is a danger that eventually, maybe in a long, long time, it could collide with one of the moons. And one of the other moons of Jupiter, called Europa, we think may have an ocean of liquid water underneath an icy crust, and it could possibly have life. And we don't want to contaminate that moon. So we're going to destroy Galileo to make sure it doesn't impact any of the moons.

I should mention that next week we're doing sort of a fire and ice theme here. Your colleague, Dr. Elizabeth Turtle, will join us. You're the fire side, she's the ice side, and we'll be talking about Europa and other icy places very different from Io. So what else? I think you're working on the Cassini project now? Yes, now I have joined the Cassini project. This mission is on its way to Saturn,

and it's going to arrive there in 2004, July 2004. And Saturn has many moons, icy moons. The most fascinating place, we think, is going to be Titan. That's a moon that is covered with clouds and haze. And I'm working with the radar instrument on Cassini that's going to be able to penetrate and image these clouds and haze so we can see the surface for the first time. Would you be surprised if you saw volcanic activity on Titan?

Not totally surprised, no, although we're not expecting it to be like Io, but we think there may be icy volcanism or cryovolcanism, as we call it. Oh, fascinating. But I think whatever we find there is going to be fascinating. And you must be having a good time with this. Oh, yes, and exploring the solar system and knowing that you're going to see a completely new place. It's really a wonderful feeling.

Dr. Lopez, thanks very much for joining us on Planetary Radio. You're welcome. Dr. Rosalie Lopez is at JPL, Jet Propulsion Laboratory, near the Planetary Society headquarters in Pasadena, California. And we have been talking about her field, volcanism, both the terrestrial type and the far-flung out there on hot little Io. Planetary Radio will continue in just a moment. Hi, I'm Emily Lakdawalla, back with Q&A.

The biggest active volcanoes in the solar system is not only not on Venus, Earth, or Mars, it's not even on a planet. The distinction goes to Io, Jupiter's innermost moon. When the Voyager spacecraft flew by Jupiter in 1979, scientists were astonished to discover volcanic plumes erupting high above Io's surface. They were even more surprised when the Galileo spacecraft observed that the surface of Io had changed dramatically since Voyager's visit. In particular, the volcano Ra Patera had spewed out lava flows covering an area four times the size of Mauna Loa. But is Ra Patera the biggest volcano? Volcanoes on Io are much lower than volcanoes on Earth. Ra Patera lies only one or two kilometers above the surrounding plains. And many of Io's active volcanoes, including Loki and Tvashtar, are

calderas, which aren't mountains. They're actually gigantic circular pits in Io's crust over a hundred kilometers across and one or two kilometers deep. These pits appear to contain lava lakes covered by thin crusts of solidified rock. Got a question about the universe? Send it to us at planetaryradio at planetary.org. Be sure to provide your name and how to pronounce it, and tell us where you're from. And now, here's Matt with more Planetary Radio.

Time again for What's Up with Bruce Betts of the Planetary Society. A little bit different this week. Normally, Bruce, we're sitting across from each other at the Society, but this time we're connected electronically. Yes, we are, and I'm giddy to experience it this way. We're going to find out what Echo sounds like on the phone. Where do we start this week? We'll start, as usual, with What's Up in the Sky,

and we've got four planets to look for, depending on when you're up. We've got in the evening, Saturn and Jupiter. Saturn is high overhead in the early evening, and if you're familiar with Orion, it's above Orion. Jupiter is the brightest object up in the evening, and is in the southeast early in the evening, and overhead by later in the evening. If you take out your new telescope, Matt, and look at Saturn, for example, on the 27th and 28th, you can see Titan, Saturn's moon, about four ring lengths away from Saturn on those dates, but you can frequently see Titan as another small speck around Saturn. Well, I'm going to hope for clear weather. In the morning, if you look, got Venus once again dominating the sky in the east,

extremely bright, Mars to its upper right, dim and red, but gradually as the weeks go on, getting brighter and brighter. And if you look, the moon will pass near Venus on the 27th and near Mars on the 25th and a little bit on the 24th. I don't know if other people are feeling this, but this anticipation of us talking about Mars getting a little brighter each time we talk, up to that climactic time in July when it ought to be really beautiful, I'm excited. As am I.

And the Planetary Society actually will be having observations of it, so stay tuned for more information on that. I will. We go to this week in space history. February 25, 1972, Luna 20 Soviet mission returned core samples from the moon Sea of Fertility, Mari Focundidatus, parachuting to Earth in the USSR at that time. How much was brought back by this return mission, which is still a pretty incredible technological achievement. We still haven't done anything like this since then, right?

That's true, and a lot of people lose track, at least in the U.S., that the Soviets even did this, but they did some robotic return missions. They returned a total of just a very few pounds, so I don't know, hundreds of grams per mission typically. But they did do some drilling, so I actually got some samples from beneath the surface. Very impressive still. A little tribute to Soviet science there. Where do we go next?

Random space facts! Mercury rotates three times in two of its years. Mercury rotates three times in two of its years. So just as the moon is locked in what's called a synchronous rotation around the Earth so that we always see the same face, that's one-to-one. It rotates once for once around. Mercury is actually in a different kind of so-called resonant orbit, and it rotates three times for every two times it goes around the sun. Now, didn't we think at one time years ago that Mercury was locked in one of those one-to-one relationships

so that it had a permanently hot side and a permanently cold side? Yes, that was what was theorized and assumed. And then sometime, I believe, in the mid-60s, there was radar data that started to show that that was not true and eventually it was figured out that it was in the 3-2 resonance, which turns out to be stable as well. I want to mention one new topic, one opportunity that will only be open a little bit longer through the Planetary Society, and this is our student astronaut contest.

You can find out more at planetary.org under the Red Rover Goes to Mars link. Student astronauts will have the very unique opportunity of being in operations during the Mars Exploration Rover mission. They'll be at JPL. The contest is open if you know some students or are a student with a birthday between September 1, 1986 and September 1, 1990. So a very unique opportunity to really actively participate in a mission and operations. And the details are at planetary.org. Yes. Follow Red Rover goes to Mars. With less than a couple of minutes left,

we better move on to trivia. Another heavy topic this week, or should I say dense? Well, things often feel dense for me no matter what. In this case, last week's question, what planet has the highest average density? And our answer, Earth, with an average density of 5.52 grams per cubic centimeter. For reference, water is 1 gram per cubic centimeter. And this is one that I thought, at least if you know too much but not enough, can be a little confusing since Mercury is very close with a density of 5.43.

It doesn't have a very large iron core, but in this case it's actually the Earth beating it out. And we had a lot of entries this week. A number of them said Mercury, but most of them got it right, said Earth. And so we have randomly chosen this week's winner. It is John Vamishy, John S. Vamishy, Davison, Michigan. And he's going to win this week's T-shirt prize. John, thanks very much for entering. He did have the right answer,

which is good old Earth. Congratulations. Let's move on quickly to this week's new trivia question. And here it is, ladies and gentlemen, boys and girls. Apollo 11 and Viking 1 both landed on July 20th. How many years apart were their landings? So Apollo 11, followed by the landing of Viking 1, soft landing on Mars.

We'll let people get back to us with that. And how do they get back to us, Bruce? Go once again to planetary.org and follow the links to Planetary Radio, and it will tell you how to enter. Bruce, we're out of time. We'd better hustle out of here. All right. Well, thank you, everyone. We're on the website every day of the week, twice on Sundays. Don't forget to hit the server.

Thank you very much, Bruce. Isn't there something else you want to say? Thank you. Good night. Bruce Betts is the Director of Projects for the Planetary Society, and he joins us each week here on Planetary Radio. Next time, we'll cool things off considerably as we go from fire to ice, including the ice flows on Mars, which have been in the news lately. We'll also visit Io's neighbor, Europa, where a layer of ice may hide a vast ocean of water. Remember that you can hear this and all of our previous shows at planetary.org.

We always look forward to your questions and comments. Send them to planetaryradio at planetary.org. Have a great week.