transcript of the PASSPORT TO KNOWLEDGE program

#101, "THE GREAT PLANET DEBATE"

Part 3: The Issues

Narrator, voice over:
Alex Storrs is a planning scientist for STSCI. His specialty is Moving Targets, primarily the planets of our solar system. His position provides an expert overview of all our options.

ALEX STORRS: Jupiter is big, it's the biggest planet, it's got the gaudiest belts, it fills your field of view, if you are taking a picture of it, an image of it. It's dynamic, it's changing, it's interesting, we know very little about it, even after Shoemaker- Levy, we really know very little about what's going on below the cloud tops, and the cloud tops are just a very small part of that planet.

RETA BEEBE (she speaks over Voyager and HST images of Jupiter):
There's basically two kinds of planets in the solar system: there's the Earth-like planets, and there are the large gas planets, and I consider Jupiter to be the most accessible of those large gas planets.

As you go farther and farther out into the solar system, the outer regions of these planets get colder and colder and you have to stare deeper and deeper through hazes to see the cloud structures. In Jupiter's atmosphere you can see the active motions of the clouds which are marking what the atmosphere is doing.

What I would most like to know is, what are the processes that make the winds blow on Jupiter? The winds are much, much stronger and I can rationalize the fact that well, yes, because it's such a dense bank of cloud there is really no solid surface, there isn't all the friction like there is on the surface of the Earth to destroy the wind. But when I look at the wind pattern from the Equator up through 7 degrees North latitude, 15 degrees, 23 degrees, I find jets and the wind increases surprisingly rapidly and then drops off surprisingly rapidly, and I don't understand the processes that create such narrow jets.

We have jet streams in the Earth's atmosphere, but they are quite broad, and here the better the spatial resolution I get on my images the narrower my wind jets are, and I do not understand that process and I really would like to know.

ALEX STORRS, over animation of the Galileo spacecraft:
As well there is the Galileo spacecraft now. Voyager was a snapshot of Jupiter, a couple of snapshots of Jupiter, but... but Galileo is actually staying there over several months and observing Jupiter over a period of time, and the Space Telescope observations would help to interpolate between the observations... detailed observations of Galileo. There's an awful lot going on with Jupiter and it would be an interesting topic from that point of view.

RETA BEEBE:
We have the Galileo probe going in on December 7th, and we know the latitude and longitude relative to the core of the planet; but the winds are blowing across that from West to East in such a way that they are carrying the clouds around the planet, and the clouds will be shifting eastward seven and a half degrees a day, so that the nature of the cloud area that the probe is going to go through is a big question.

We have Hubble Space Telescope observations in October and scheduled for February, and we will assume that the winds do not speed up or slow down and we will interpolate and say that is the cloud that it went in. But if we had even just one orbit in March to compare with the February and the October it would help to substantiate the fact that that assumption is true and then the students who were collaborating here could also access these images, and that would allow them to see what's happening, they would be allowed to access the Web pages that have been assembled at Ames Research Center about the analysis of the probe. Because by the time the students get their observations in March the people at Ames will be reducing the probe data, so there's a lot of interaction there. And this would be a valid interaction because it would further substantiate the condition, how rapidly it was changing.

ALEX STORRS introduces possible observations of Pluto and Charon: imagery from Lowell Observatory and JPL and HST:
Pluto and Charon (Charon is Pluto's moon) are an interesting topic for a wide variety of reasons. Pluto just passed perihelion, that's the closest approach to the Sun, and in fact it was closer to the Sun than Neptune was at that point. And this is the time when you would expect a lot of changes in Pluto, and therefore it's good to keep a close look at what's happening on Pluto over the period immediately after perihelion. It's like the period right after Summer. Everything has been very hot and it's going to start to cool down, we'll start to see things raining out, and we expect to see some changes. We don't know what changes we'll see and we don't know what time-scale they will occur (on), and therefore we have to keep a close eye on it to see if there is anything that's changing over a very short time-scale. After a few years, if we don't find any changes, maybe we'll be able to relax a little bit, going into a longer term monitoring program.

MARC BUIE (interviewed in front of the telescope at the Lowell Observatory where Pluto was discovered by Clyde Tombaugh):

Pluto just in 1988 passed perihelion, which is the point at which it's closest to the Sun and it's going to begin... it began then its hundred and twenty-year voyage to its most distant place in its orbit. And over this time Pluto is going to receive less and less of sunlight and basically cool off, so we have now an opportunity to study Pluto when it's at its warmest, and if we don't take that opportunity now to make these observations, we'll have to wait another two hundred and forty years to repeat the experiment.

Pluto, for young people (and I consider myself still young even though I may not look it anymore!) Pluto is one of the... it's sort of the last "astronomer's planet". We haven't yet had a close-up view with a space craft. We have an opportunity here to see the development of a science and the knowledge base about Pluto develop in our lifetimes. And certainly the past ten years have been very exciting watching what we've learned about Pluto, and I'm sure we'll be learning a great deal more, but this is sort of a ... the special epoch in human history where we are learning for the first time what this planet is all about.

The most exciting thing that could come out of this observation, I think, is that we could take a picture... let's say a set of three pictures... get a map of the surface, and compare it against the map that we did three years ago and look and find a real change, some patch on Pluto is now brighter or darker. And this will start to tell us something very important about how fast the surface might be changing in response to its changing seasons. And I would consider that to be a very... a fundamental discovery.

ALEX STORRS introduces the possibility of studying Neptune: Neptune has ring-arcs, as well. These have been discovered through occultation observations and imaged to a certain extent by Voyager. It would be good to observe them again, to see how they change with time. The time variation is a recurrent theme in observations of the solar system.

HEIDI HAMMEL:

One of the biggest surprises when the Voyager spacecraft flew by Neptune was a huge dark spot on the planet, and we called it the Great Dark Spot. We are unable to see it from Earth because Neptune is the most distant planet from us right now, and it's very hard to see things there. When you looked with the Hubble Space Telescope last year that Great Dark Spot was gone, it had simply disappeared, it wasn't there anymore, which was a big surprise! But when we looked very, very carefully we saw a different big dark spot on the planet, in the Northern part of the planet -- the other one was in the South. So that means Neptune's atmosphere just turned upside down! When we would look at Neptune this time we don't know what we are going to see. There might be a whole new dark spot, and that dark spot would belong to the students, they would have discovered it.

One thing that we all care about is the weather, and we care about the weather on the Earth the most. But what makes weather is gases and clouds, and the reason the weather on the Earth is hard to predict is because we have oceans and continents that interact with our atmosphere. That makes it very hard to predict the weather, as we all know. But if you take a planet like Jupiter or Neptune you don't have continents and you don't have oceans. All you have is gas, all you have is atmosphere, and therefore it's a lot easier to model the weather on those planets. But it's the same physical process, it's the same kind of thing happening, whether it happens on the Earth or whether it happens on Neptune. Therefore by studying weather on Neptune we learn about weather in general, and that helps us understand the weather on Earth better.

ALEX STORRS introduces the option of studying Uranus:
Uranus is a... fairly intriguing body. We just made some observations of Uranus looking at some very faint satellites that Voyager discovered as it flew by, but then Voyager left, and nobody observed them until we hit them with Space Telescope and were able to refine their orbits a little bit, tell what they are, get some... get a better idea of what color they are, and therefore have a hint of what they are made out of.

As well, Uranus has rings, and nobody had really observed the rings very much since... since Voyager flew by, and it would be very interesting to again observe some of these small satellites now that we know where they are, and to observe some of the rings and try to get a better idea of their color and their composition.

CAROLYN PORCO over NASA JPL animation of Voyager at Uranus, and Voyager images:
Uranus is a very puzzling object. It's tilted, relative to its orbit, it's tilted; its spin axis is tilted some ninety-eight degrees, so it's one of the two or three oddball planets in the solar system that has such an exaggerated tilt. But it's the only large gaseous planet that falls into that category, so that obviously it went through a very catastrophic event, people believe it got hit by an Earth... Mars- or Earth-sized object, sometime when it was forming, which tilted the planet on its side and caused it to have this bizarre rotation. And all the objects in it or around it, the rings and the satellites, are all in the equatorial plane, so they formed afterwards, obviously, or else they wouldn't find themselves in the place that they do, so that's puzzling. Is that what really happened?

So you need to have the Space Telescope, for example, to get good visible pictures of the rings, and to see some of the ten satellites that were discovered by Voyager.

PORCO points out the objects on a recent HST still she holds up to camera:

OK, there are ten satellites in close orbit around Uranus. We have known, of course, before that Uranus was encircled or orbited by five larger satellites, but Voyager found ten smaller satellites, and they are close enough to Uranus that in a ground-based telescope you can't really see them because the glare and the scattering by Uranus in a ground-based telescope prevents you from seeing them. But just recently images were taken with the Wide Field/Planetary Camera, of Uranus and its satellites that were impossible before, and this image -- although we are not resolving any of these objects -- we can clearly see the rings of Neptune are not resolved. OK, we can't make out details within any of the rings, but nonetheless less they are pretty easy to see, and here are some of the ten satellites that were discovered by Voyager, and we can also see Miranda, and Ariel, which are the two satellites that we knew existed even before Voyager got there.

HEIDI HAMMEL on the overall LHST project:
When the students are looking at the various options they have, whether it's Neptune, Pluto, Jupiter or Uranus, they are going to be asking "what's the most interesting thing that I can do?" and that's what science is all about. That's what scientists do all the time. They say: `I want to study this. What's the best way to do that? What's the right way to make the observation, how can I best use my observing time to answer a question?' That's what science is all about, and that's what this project is going to allow the students to do.

Narrator BILL GUTSCH to camera:
By now you probably realized that Live from the Hubble Space Telescope is not your usual "field trip". There'll be no packed lunches, and no school bus, because you are not going to be traveling on regular highways around your town; instead you are going to be traveling on the Information SuperHighway, and here is when you need your pencil and paper, because we are going to tell you now where you can find out more information about the project on the World-Wide Web.
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