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00:00During this program, we are going to see beautiful pictures of the largest planet in our solar
00:15system, Jupiter.
00:16We will also see some of its 14 moon moons in surprising detail.
00:23These pictures are better than the pioneer spacecraft pictures of Jupiter we saw during
00:27the previous program.
00:29I'm Larry Ross, Director of Space Programs at NASA's Lewis Research Center in Cleveland,
00:34Ohio, and I'm your host for this 10th program in our series of 13 called Journey Through
00:39the Solar System.
01:10Now, let's see a videotape made after the Voyager 1 spacecraft had its closest encounter
01:27with Jupiter in 1979.
01:30Rodney Mills of NASA describes the Voyager pictures.
01:34This is an image of Jupiter we obtained from a distance of something like 50 million miles,
01:39and we were immediately struck by the fact that it looked somewhat different than it
01:43did when an earlier spacecraft, the Pioneer, flew by in about 1973, 1974.
01:49In what respect?
01:50The bands?
01:51The bands and the zones look different.
01:55The appearance of the great red spot looked different, and a number of other features.
02:00So it's very dynamic.
02:01It's a very dynamic place, yes.
02:04Is it solid?
02:06Jupiter may have a small solid core about the size of the Earth, but for the most part,
02:12it's a large bag of liquid and gas, mostly hydrogen.
02:18Now, we don't ever see the solid surface.
02:21All we see are the cloud decks.
02:23We don't know what gives them the color.
02:25We have some suspicions, and maybe some of our data will reveal that.
02:30In the years ahead, we have a mission that will take a satellite to Jupiter and penetrate
02:35these gases.
02:36Do we not?
02:37That's right.
02:38We have a mission on the books right now which will include a probe that will go down and
02:42penetrate into the surface and actually into the surface of the clouds and actually take
02:48some measurements.
02:49That'll be exciting.
02:50Let us go to the other details.
02:53Well, I think this is one of the more beautiful of the photographs showing two of the satellites
02:58passing in front of the planet.
03:00Now, Jupiter has about 13 satellites or moons.
03:05Four of them are very large.
03:07They're the ones which Galileo discovered, and in this photograph, you can see two of
03:12those moons passing in front between the spacecraft and Jupiter.
03:17How about the sizes?
03:20The satellites are large.
03:23They're large.
03:24Actually, two of them are larger than the planet Mercury.
03:28These four Galilean satellites are Io, the one closest to the planet.
03:35Then comes Europa, then Ganymede, then Callisto.
03:39Two of those are larger than Mercury.
03:42Three of them are larger than our own moon.
03:44So they're all really planets in their own rights.
03:47What we have out there at Jupiter is really a miniature solar system.
03:49We have a large body which is radiating more heat than it receives.
03:54Possibly another sun.
03:55It's a sun that didn't quite make it.
03:58And the density of these satellites varies considerably, just like the densities of our
04:04own planets vary, yes.
04:06The ones closest to the central body are hard rocky objects, and the ones further away are
04:12less dense.
04:14This is a close-up view of the Great Red Spot.
04:18This is a feature that anyone who has a small telescope can possibly identify on Jupiter.
04:24Galileo observed the Great Red Spot.
04:27So we know it's been in existence something like 300 years.
04:31Now, it moves around the planet a little bit, but it never loses its identity completely.
04:37And this is amazing, considering it's really just a storm in a cloud formation.
04:41That's large, too, as I recall, about the size of three diameters of the Earth.
04:45It's as wide as three diameters of Earth.
04:48So it's a large storm.
04:50Now, we were very interested in where the energy comes to make this thing exist, and
04:56we were interested whether it was rotating or not, and we have found that out.
05:00We have found, for instance, that it rotates once every six days.
05:05I should mention also that Jupiter has a lot of energy.
05:09It spins on its axis so that a day on Jupiter is only 10 hours long.
05:14Aesthetically, the photographs are beautiful.
05:18Let me show you some examples of the beautiful, arty photography that's come out of the mission so far.
05:24This is a view of a portion of the planet Jupiter in its normal color.
05:29Now, as an aid to trace the flow of the atmosphere, we introduced some artificial coloring,
05:35and it comes out very remarkable.
05:38This is an example.
05:41We're then going to learn a lot about the dynamics of motion and the flow patterns.
05:47In fact, we photographed the planet Jupiter continuously over a period of a month with still photos,
05:54and now we've assembled them into a movie which we can run and speed up the motion,
05:59and you can actually see the flow of the atmosphere and the appearance and disappearance of clouds,
06:06and our scientists are busily engaged in analyzing that.
06:10It certainly looks different than anything we've seen in any of the other planets.
06:13What else do you have here?
06:15Well, before I leave it, let me show you a spread-out map of the entire planet Jupiter.
06:20This is a new result that's just released this week.
06:23This is the equivalent of a Mercator projection.
06:27It shows all sides of Jupiter at one time,
06:31and it's unusual in that most of us didn't realize how many various plumes and spots there are on the planet,
06:37and all of these things move in the movie that I spoke about.
06:42Do they all go at different speeds, relative?
06:45Yes, they go, in fact, and tend to go in opposite directions.
06:48Some of the bands flow one direction, like eastward, and some flow westward.
06:53Lots of questions.
06:54Yes, lots of questions.
06:55And some of the dark spots we had seen and some of the white spots we had seen prior to this.
06:59Some of the white spots down in the southern latitudes have been observed for around 30 or 40 years.
07:05I mentioned that the Great Red Spot has been observed for 300 years.
07:09Some of the features appear in a matter of a few days or a few weeks, and then they disappear.
07:15To go on, there are several other features that I should mention about Jupiter.
07:21We made a remarkable discovery, and we found that there is a ring around Jupiter.
07:26I understand that.
07:27Right.
07:28Now we know that, of course, Saturn has these beautiful silvery rings,
07:32and a short time ago we found that Uranus has some thin rings,
07:36and now Jupiter has joined the club, so it leaves Earth out almost.
07:40This illustrates where the camera was aimed.
07:44We took a single exposure out in this area where the little square is located.
07:50At the time we crossed the equatorial plane of Jupiter with the spacecraft,
07:56and we took a single 10-minute exposure, and I'll show you the resultant photograph.
08:02This is a black-and-white photograph, and it takes a little explanation.
08:06These strange wiggly marks up here are actually images of stars
08:12because the spacecraft was moving during the 10 minutes,
08:14so the stars actually left little jagged traces.
08:18But in the central portion of the photograph, you'll see these straight lines.
08:22Actually, there are six separate images.
08:25That's right, yeah.
08:27And that's the edge of the ring looking straight on at it.
08:32Yeah.
08:33Now the ring is very dark.
08:34It's fairly thin, probably not thicker than 20 miles or something like that.
08:40It's composed, we think, of rocks, and they're very dark.
08:44But we'll be taking more images of this with Voyager 2.
08:49Now that we know it's there, right.
08:53And since we discovered it, I believe there has been an observatory here on Earth
08:57that has also confirmed the discovery.
09:00This photograph of Jupiter has had a ring drawn on it by an artist
09:05to give you some idea of the size of the ring.
09:08Although we know approximately its thickness,
09:11we really don't know the extent of it inwards towards the planet,
09:14and we will be measuring that with the next spacecraft.
09:17Are these rings always in the equatorial plane of the planet?
09:20Yes, right.
09:21In fact, that's a requirement almost.
09:24Possibly something that never was quite formed into what it should have been into another satellite?
09:30It could be the broken up debris of a small satellite, and that's probably likely.
09:38There is another object that's fairly close to the planet Jupiter,
09:42and this is the small satellite Amalfi.
09:45It's really not one of the Galilean satellites, but it's the innermost satellite.
09:50And this had never been seen by mankind before as anything other than a point of light.
09:55In fact, very few astronomers had ever seen it.
09:57It's really a small rocky object.
09:59It's not spherical in shape.
10:01Its approximate size is like 80 by 150 miles.
10:05It's very dark, very red.
10:08It may be just a captured asteroid.
10:10Traveling pretty rapidly probably, too, because it's close to the planet.
10:15As the spacecraft swung behind the planet Jupiter,
10:19we took occasion to take some images of the dark side of the planet,
10:23and we made another remarkable discovery.
10:27This is a photograph.
10:28It appears rather noisy, but in fact it contains quite a bit of information.
10:33This light arc across the top here is actually an aurora display,
10:38like the northern lights here on Earth.
10:40The atmosphere is being excited by charged particles spiraling in.
10:45Then down lower in the photograph there are some bright white spots,
10:49and we believe that's evidence of lightning,
10:52lightning above the cloud tops.
10:55The same sort of thing is seen sometimes here on Earth down in the tropical areas,
10:59and they're called superbolts.
11:01It's a great deal of energy.
11:04These measurements were later confirmed by our spacecraft.
11:07On the spacecraft an instrument to listen to the planet,
11:10and we heard electrical waves corresponding to whistlers,
11:14which are created by lightning.
11:18What about some of the other satellites?
11:21Let me speak about the satellites not exactly in the order we observed them,
11:24but the outermost of the four large satellites is Callisto.
11:30Now Callisto is not very dense.
11:32We know that it has a density not about halfway between water and rock,
11:37so we know that it must be composed about half of ice.
11:41It's rather a cold object.
11:42It has no atmosphere.
11:45This is a color photograph we obtained of Callisto as we flew by it,
11:50and we were immediately struck by the fact it's heavily cratered,
11:54probably more heavily than the moon is even.
11:57This is evidence that it's not changed much in the last four to six billion years.
12:04No atmosphere.
12:06There's apparently no volcanic action, and it's stayed frozen.
12:11It has rings or appears this way.
12:14Right. There is one large impact basin up there
12:16where it looks like some very large object had struck it
12:19and formed concentric rings around the basin,
12:22and those have been apparently frozen in the ice.
12:26And elsewhere you can see some small craters that are very light appearing.
12:30It looks like the dark covering on the planet has been thrown aside,
12:36and it's exposing probably ice.
12:38Are there newer ones possibly, newer craters?
12:41Well, we think probably it was cratered at about the same time in history
12:45that the Earth and the moon and Mercury were,
12:47and that was back way before our time, probably four to six billion years ago.
12:52But it hasn't changed much since then.
12:56This is another photograph in color of the entire planet, Callisto.
13:03Actually, it's a satellite, but it really deserves to be considered as a planet.
13:11And finally, a third photograph of Callisto,
13:14which shows in black and white a little more of the cratering detail.
13:18It certainly has been impacted.
13:20It's pockmarked with a wide range of sizes.
13:23Also, if you notice along the limb or the outer edge of the satellite here,
13:27you'll notice there isn't much relief.
13:29Apparently there are no mountains,
13:31and that's consistent with the theory that there's a lot of ice in the satellite,
13:36and it really couldn't support mountains.
13:39Next, moving inward, I'll talk a little about Ganymede,
13:44which is probably one of our favorite satellites
13:46because it has such a diversity of appearance.
13:50Again, here's a full image of Ganymede.
13:53You can see it's a different color and has a different texture.
13:56There are light areas and there are dark areas.
14:00We think the dark areas are a little bit older and the light areas are a little newer.
14:04There's some evidence here that the surface has been under a lot of stress
14:08and it has been altered during the eons of time since it was formed.
14:13There are a fair number of craters, but not as many as on Callisto.
14:18This would be dense, now more dense than what we had seen before.
14:21Right.
14:22More rock, possibly.
14:23A little more rock, but still an appreciable amount of ice and water,
14:28of course, if it were warm enough, but it isn't.
14:30Right.
14:33This black-and-white photograph illustrates the rough texture we see on portions of Ganymede.
14:40This looks a little bit like some dune buggies have been running around in the sand.
14:44Actually, the scale is quite a bit larger.
14:47Either the surface has been compressed or stretched and given rise to all these ridges.
14:55We have impacts as we see there.
14:57Yes, so you can see that whenever that happened,
15:00it was still before the end of the cratering action took place.
15:07Our geologists are having lots of fun with these images.
15:11One more rather remarkable photograph here of an area showing both the light and dark surfaces,
15:18and we have an example here of a fault line.
15:21It's the only place besides the earth we've seen any evidence of earthquake fault lines.
15:27I'll try to point it out down here.
15:29You'll see a displacement down in this region of the lighter area where it's been moved.
15:36On the left, the whole portion.
15:38Right.
15:41We've not seen this any other place?
15:43No, not on the moon, nor Mercury, and not on Mars.
15:47Of course, we haven't seen the actual solid surface of Venus,
15:50but so far this is the only other place in the solar system.
15:58Now, moving into the next satellite.
16:04This is an image of Europa.
16:08Now, this is a Lockheed satellite.
16:12This is actually the best photograph we obtained with Voyager 1.
16:15It didn't come very close to Europa.
16:18We'll do much better with Voyager 2.
16:20Our pictures will be about ten times larger with Voyager 2.
16:24But there's a very interesting feature here on this satellite.
16:28You see these long, straight lines down in the southern hemisphere?
16:32We don't know what they are.
16:34They could be just surface markings,
16:37or they could actually be crevices, long, huge canyons.
16:41If they are, they're much greater than our own Grand Canyon.
16:46They stretch thousands of kilometers.
16:48What's the size of the planet itself?
16:51This, again, is smaller than the Earth, but it's comparable to the moon.
16:58Whatever they are, lines that are a quarter of the distance on the surface,
17:02or more even.
17:04So we're looking forward to the next trip by this satellite.
17:08Io is a pretty interesting satellite.
17:11We have some people with remarkable imaginations,
17:13but none of them had imaginations good enough to expect what we found on Io.
17:20It's a very remarkable object in the solar system.
17:24This is a color photograph showing it has a very goldish, reddish color
17:29with some white areas.
17:31Now, we expected Io to be a little different,
17:34and we expected it to have some salt flats on it, and I think it does.
17:39But one of the first things we noticed is there seems to be no evidence of cratering.
17:44These other bodies have all shown craters from impacts,
17:48and so why shouldn't Io?
17:51Maybe as we got closer we'd find more, but we didn't.
17:55We should have been suspicious of a few of the other features.
17:58This rather strange-looking ring feature here about in the center
18:03doesn't look like the sort of thing you'd find on the usual satellite.
18:07That's not an impact?
18:08No, no, it is not.
18:10We don't know what it is.
18:11We do now.
18:12Oh, we do now, all right.
18:13We didn't know at the time.
18:14We didn't know at the time.
18:15First saw the photograph coming back from the spacecraft.
18:17I see.
18:18As we got a little closer to the satellite, we saw images like this.
18:23Now, this was evidence of lava flow.
18:26It looks like a collapsed caldera
18:30and a very thin spreading of the dark material, which was thought to be lava.
18:36It wasn't until several days after we had gone by Io
18:39that one of the lady engineers on our navigation team
18:43was working with some of the photographs,
18:46and she was trying to fit the circle of Io into a computer program,
18:52and it wouldn't fit because it had a funny-looking bump on one side of it.
18:55You can see it if you look very closely down here, a strange-looking bump.
19:00Well, it turned out that that was not an artifact of the imaging system.
19:03That was real.
19:05So we finally concluded, hey, we have a volcano, an active volcano.
19:09An active volcano.
19:10Spouting out as we flew by.
19:13And not only was there one, but if you look at this other bright spot in the image here,
19:17you can see something is spouting up there.
19:20See, that's a portion of the satellite that's in the shade or the dark side.
19:25Right.
19:26But the material is actually being ejected high enough so it's catching the sunlight.
19:31There's no atmosphere on Io,
19:33so any material coming out of a volcano tends to follow a ballistic trajectory
19:38and it falls back to the surface.
19:40The height of these plumes is something like 150 miles.
19:44A lot of material coming out.
19:46So suddenly we understood why the surface didn't have any craters.
19:50Yes.
19:51All covered up.
19:53Apparently this has been going on for billions of years.
19:56Very active.
19:57At the present time now, we have identified seven active volcanoes
20:01which were erupting during the few days that we flew by it.
20:05You couldn't see anything like that if you flew by Earth.
20:09Volcanoes just don't go off that frequently here.
20:13I have several other photographs that demonstrate this a little more clearly.
20:17Here is a spout on the limb of the planet,
20:21and again you can see the big fountain of material.
20:24Now we have pretty strong evidence that there's a great deal of sulfur
20:28coming out of these volcanoes,
20:30and that's covering the surface with sulfur
20:32and a fair amount of it is also getting into the magnetosphere
20:36and leaving the satellite.
20:40Here's another photograph of another volcano here.
20:44You can actually see the dark material coming and spouting out.
20:48And finally a color version,
20:52a rather famous photograph showing an eruption right on the limb of the satellite.
20:58It's approximately in true color.
21:03For scientific purposes, sometimes we enhance these photographs,
21:06and this is a composite photograph that includes some ultraviolet measurements,
21:11and you can see up here the eruption,
21:14and it enables us to determine the particle size coming out of the vent.
21:19So Io, I think, is nominated as the most remarkable object in the solar system.
21:26It's a very active volcanic object,
21:31and it's probably been going on for billions of years,
21:35and the surface is fresh, it's new,
21:38and it's continually changing day by day.
21:41Here at the Lewis Research Center in Cleveland, Ohio,
21:44we are directing work on modification of the Centaur rocket for use with the shuttle.
21:50Centaur will be used to launch the Galileo probe to Jupiter in 1986.
21:55Centaur will be carried into low Earth orbit.
22:01The rocket will be released from the shuttle, moved to a safe distance,
22:05and fired, sending Galileo to Jupiter.
22:15During the upcoming Galileo mission,
22:17we hope to learn quite a bit more about Jupiter and its atmosphere.
22:21Let's go to a film called Galileo Mission to Jupiter,
22:24which outlines the project.
22:36The spacecraft carries a parachute-equipped probe
22:39targeted for deployment into Jupiter's turbulent atmosphere.
22:44The probe will allow our first direct sampling of the Jovian atmosphere
22:48and is a forerunner of future probes designed to explore the sun,
22:53Saturn, and satellites like Titan with considerable atmospheres.
23:00The probe will descend into Jupiter to analyze and directly sample its atmosphere,
23:05believed to be original material from which the solar system formed 4.6 billion years ago.
23:18The Galileo mission, named for the Italian astronomer
23:22who discovered Jupiter's four large satellites,
23:25has been designed to use the gravity of those moons
23:28to bend the spacecraft flight path during its 24-month tour of the Jovian system.
23:36As the probe samples the Jovian atmosphere,
23:39scientific results will be relayed to the orbiter
23:42for one hour before the probe's signal is lost at pressures of 10 to 20 Earth atmospheres.
23:49Galileo makes a close flyby of Io to study the moon's volcanic surface.
23:56Io's gravity in turn bends the trajectory of the spacecraft,
24:00helping to send it into orbit around Jupiter.
24:04Flying just 1,000 kilometers above the surface,
24:08images of the moon show features as small as 50 meters.
24:13After relaying probe science data to Earth,
24:17the spacecraft will orbit Jupiter at least 11 times,
24:21making a close flyby of one of the Galilean satellites on each orbit,
24:26yielding high-resolution images and detailed measurements of their surfaces,
24:31gravity, and magnetic fields.
24:34As the orbit rotates about Jupiter,
24:37the spacecraft will sample all regions of the planet's vast magnetic field.
24:45The first full orbit of Jupiter brings Galileo to its first encounter with Ganymede.
24:51The gravitational effect of the close equatorial flyby
24:55reduces the length of the spacecraft's orbit from 200 to 90 days.
25:01Using photographic data from Voyager,
25:04this computer-simulated flyby of Ganymede shows Galileo's view of the icy moon.
25:22Galileo will fly even closer to Ganymede in its second encounter with the moon.
25:28Each satellite flyby modifies Galileo's orbit,
25:32sending the spacecraft on to its next encounter.
25:36Each flyby is 20 to 100 times closer than the Voyager encounters.
25:42The Voyager saw only the equatorial regions of these icy moons,
25:47but Galileo will photograph the north pole of Ganymede,
25:51providing a new perspective in the study of these large satellites.
25:55A flyby of Callisto occurs on the sixth orbit of Jupiter.
26:11The ancient cratered terrain of Callisto is closely studied
26:15as Galileo passes over the southern hemisphere of the outermost Galilean satellite.
26:26The spacecraft will sweep within 200 kilometers of the surface of Europa
26:38at the end of its eighth revolution about Jupiter.
26:42Galileo's Europa encounters will give us our first detailed look
26:47at this moon's mysteriously fractured surface,
26:50which is seen by other spacecraft no better than we see Earth's moon through a small telescope.
26:56During its 20-month mission, Galileo will expand our knowledge of Jupiter and its satellites,
27:02revealing in detail the bodies and workings of this miniature solar system.
27:09Through the years, we will learn more and more about the universe in which we live.
27:14Galileo is just the beginning of what is possible.
27:17This is Larry Ross saying goodbye from the NASA Lewis Research Center in Cleveland, Ohio,
27:22until next time, when we will travel to the next planet out from Jupiter,
27:31the great ringed planet, Saturn.
27:38NASA Jet Propulsion Laboratory, California Institute of Technology
28:08NASA Jet Propulsion Laboratory, California Institute of Technology