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
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
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.
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.
|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
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
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.
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