Planetary Radio: Space Exploration, Astronomy and Science - Uranus and Neptune Take Center Stage With Heidi Hammel

Episode Date: December 19, 2005

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Uranus and Neptune take center stage this week on Planetary Radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. And we're once again taking you to the outer reaches of our solar system as we talk with planetary scientist Heidi Hamel. I'm Matt Kaplan. on the phone to provide his latest look at the night sky. And there's a lot to see in the next two weeks, including a promising meteor shower. I bet you're wondering if there could possibly be any other news from around the universe this week. Why, yes, Virginia, there is. Tick, tick, tick. Just four weeks ago on this program, we heard Alan Stern talking about the relatively short launch window

for his Pluto Kuiper Belt probe. Well, the start of the mission will be delayed several days while NASA takes another look at the rocket under New Horizons. The double-check should still allow the spacecraft to save years of travel with a gravity boost from Jupiter. The saga of Hayabusa continues, with the spacecraft in safe mode and suffering from several problems, Japanese mission controllers had no choice but to delay sending the order to return to Earth. It could be 2007 before they can try again. Details are at planetary.org.

Dust off those old plans of yours for a warp drive. NASA's National Institute for Advanced Concepts is once again accepting proposals for funding. The deadline is February 13, 2006. Phase 1 awardees can get as much as $75,000 for six months of initial study. We'll put the link up at planetary.org. And we'll have to get NIAC director Bob Casanova back on the show after they've made their selections. Whether you're on Earth, the Moon, or Mars, camera technology has sure come a long way in the last 40 years. Here's Emily with the history of how we get snapshots

from space. Say green cheese. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, If digital camera technology was only available from the late 1990s, how did earlier spacecraft take and record pictures for communicating back to Earth? Present-day spacecraft, including both Cassini and the Mars Exploration Rovers, take pictures using digital cameras equipped with charged coupled devices, or CCDs. CCDs form the guts of most off-the-shelf digital cameras today.

But before the invention of the CCD, many spacecraft were equipped with an analog detector known as a vidicon, a type of TV camera. For example, each Voyager had two vidicons, one hooked to a wide-angle lens and one to a narrow-angle lens. Incoming light was projected onto Viticon tubes coated with selenium sulfur. The detectors were then scanned by an electron beam. The scanning produced a fluctuating voltage which was either converted directly into a radio signal for real-time broadcast to Earth

or was stored on Voyager's 8-track digital tape recorder. It took 48 seconds for the electron beam to read out each image from the detector. What did they do before the invention of the Viticon? Stay tuned to Planetary Radio to find out. Heidi Hamel used to get carsick when she was a kid. Stretched out in the back of her parents' sedan, she could watch the stars through the rear windshield. Soon she was learning the constellations and falling in love with the sky.

When Comet Shoemaker-Levy 9 smacked into Jupiter 11 years ago, she led the Hubble Space Telescope investigation team. she led the Hubble Space Telescope investigation team. Nowadays, she spends much of her professional life studying Uranus and Neptune with some of the world's most powerful telescopes. The senior research scientist at the Space Science Institute in Boulder, Colorado, has helped reveal that these beautiful gas giant planets are much more dynamic places than anyone suspected just a few years ago, and worthy of much deeper study. Heidi Hamel, thanks very much for joining us on Planetary Radio.

It's a pleasure to be here, Matt. We are partially, at least, remedying a mere oversight on the part of this program. We have given short shrift to a couple of large planets, not the largest. Uranus and Neptune have not only gotten short shrift from us, but sometimes it would appear in the scientific literature. That ignorance has been very ill-deserved, and a lot of the work that you've done in recent years has shown that these planets are actually pretty dynamic and pretty exciting places.

Before we get into that, I wonder how much of what you've been able to learn in the last few years, you and your colleagues, is thanks to that wonder of astronomical technology, adaptive optics. Well, I have to say that quite a bit of what we're learning in recent times is due to adaptive optics on our ground-based telescopes. It's not the only tool that we use. We also use the Hubble Space Telescope. But adaptive optics from the ground certainly helps us tremendously at the near-infrared wavelength, which is a wavelength of light where there's a lot of interesting structure to be seen

on these ice giants at the edge of the solar system. You should probably tell people a little bit, for the few in our audience who don't know what we're referring to, what adaptive optics is all about. Well, I'll tell you, adaptive optics has been a marvelous thing. Really, what it does is, in a very simplistic way of thinking, it takes the twinkle out of the starlight or the twinkle out of the planet's light. By locking our telescope onto a planet such as Neptune or Uranus, we can track very carefully that planet's motion due solely to atmospheric turbulence between us and the planet.

In other words, turbulence in our atmosphere. us and the planet, in other words, turbulence in our atmosphere. And we can compensate for that motion, sort of do the inverse of the motion to really quiet that motion and make a much clearer, stiller picture of the planet. So it takes what would normally be a very fuzzy image of Uranus or Neptune or any astronomical object and tightens that image up to a much sharper image. And these changes, our ability to do this, has really increased tremendously, literally, in the last few years. For example, we've been looking at the planet Uranus with one of the Keck telescopes up on Mauna Kea,

the Keck 2 telescope and its adaptive optic system. And we have a series of images starting in the year 2000, and every year we go back to the telescope and we take another image. We're doing that for a very interesting reason, which I can get to in a minute. But what we see in our images is that we have been learning how to optimize the adaptive optics to do a really good job on the planet Uranus. And every year, our images have gotten just a little bit crisper and a little bit clearer. And when you're looking at a planet at the edge of our solar system,

even the tiniest little bit of improvement helps tremendously. We're going to put up links to a number of articles on the Planetary Society website that document your success, and one of them illustrates exactly what you're talking about. Year by year, this really dramatic improvement in the image quality. That's right, yeah. And we're really exploiting that to study aspects of the system of the planet Uranus. I think that Uranus has gotten short shrift. I call Uranus the Rodney Dangerfield of the outer solar system.

No respect. It's gotten no respect. And part of it is because of the unfortunate way that some people pronounce its name. And part of it is just from the Voyager flyby of the planet Uranus in 1986. It flew by over the cloud tops, Voyager 2, in 1986 and saw basically nothing in the atmosphere. Very bland, uninteresting, undynamic atmosphere. Just bad timing?

Just bad timing. We now know, well, we knew then, but we didn't appreciate how important it was, that Voyager flew by Uranus at the peak solstice. That's when the planet's poles pointed directly at the sun and the earth. And for reasons that we don't fully comprehend yet, but we're starting to think seriously about, it seems that's a very uninteresting time in the atmosphere. Now we are just a few years away from equinox, which is the ring plane crossing. That's the time when we see the planet sideways.

In other words, we're seeing its equator pointing at the sun. And we're seeing all sorts of interesting cloud activity on this planet that was totally unexpected and unanticipated. People had thought maybe there was some seasonal variability, but they thought there'd be a phase lag of 10 years past equinox. What we're seeing with our Keck images and with Hubble images is that the planet seems to be responding almost instantaneously to the seasonal change of its viewing angle, its aspect change.

And that's a real head-scratcher. We don't understand that. My colleague Emily Laktawalla wrote an article about a year ago titled Uranus, Boring No More, and we'll put a link to that on the website as well. Great. Is it also surprising to see this kind of very dynamic activity at a place that's so cold. Well, sure, it is cold, but you have to remember that what causes dynamic activity in a planet is not just its temperature, but the temperature balance in its atmosphere.

What you've got coming out from the inside of the planet, you know, whatever internal radiation there is in the planet, and whatever radiation you have coming on from the inside of the planet, you know, whatever internal radiation there is in the planet, and whatever radiation you have coming on from the outside. Now, these planets, Uranus and Neptune, are very far from the sun. So sunlight, you'd think, would not play a big role. On the other hand, it's very cold where they are. And in the case of Uranus, the planet itself doesn't seem to have much internal heat. And therefore, it could be that this atmosphere is in a very delicate radiative balance state.

So just the small change of sunlight you get as you progress in the seasons apparently seems to be enough to start to trigger activity in the planet. But this is really all kind of new, and really really we're just taking this data for the first time. I mean, there have been these seasons in the past, but the year on Uranus is something like 84 Earth years, and we didn't have the kind of sophisticated tools and cameras, and not to mention computing power, the last time we were in

this season, 42 years ago. Some of us were, you know, just barely old enough to walk 42 years ago. And so we're really kind of exploring this planet really for the first time at this season with our modern equipment, modern technology, and modern computation skills. We'll have more from planetary scientist Heidi Hamel when Planetary Radio returns in a minute. This is Buzz Aldrin. When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system. That's why I'm a member of the Planetary Society, the world's largest space interest group.

The Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets. We sponsor the search for life on other worlds, and we're building the first-ever solar sail. We didn't just build it. We attempted to put that first solar sail in orbit, and we're going to try again. You can read about all our exciting projects

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Welcome back to Planetary Radio, where we're about to continue our conversation with Heidi Hamel, Senior Research Scientist for the Space Science Institute in Boulder, Colorado. We've heard how Heidi and her colleagues began to learn that big old Uranus wasn't nearly so boring as people thought, but nothing compared to what she saw on a holiday evening about 18 months ago. Could you talk about what you saw roughly around the 4th of July 2004 that you called a fireworks show? Yeah, that was a really fun observational experience. That was a really fun observational experience. You know, we have been looking at Uranus now since 1986 with every camera that we can get our hands on and get time on,

and we've been looking at it at the near-infrared with Keck and even with Hubble since about mid-90s, well, 98 or so, I think, is when we took our first near-infrared images of the planet. And that southern hemisphere, that's the hemisphere that's been baking in sunlight for the last 20 years, has really never shown much activity at all, just like Voyager saw. Most of our excitement in the late 90s and the early 2000s was in the planet's northern hemisphere. That was the hemisphere that was first getting sunlight. And that's where we saw all these big bright clouds and got us all excited about Uranus.

But the southern hemisphere stayed uninteresting until the 4th of July. Imke de Potter and I were observing with the Keck telescope, and there was a huge bright feature in the southern hemisphere at a wavelength that we've looked at for years and never seen southern features before. And when we compared it with some of our other wavelengths of light, we could see that this was a bright cloud feature that we had seen those kinds of clouds before, but they had never risen to a high enough altitude to allow us to detect them at this particular wavelength of light.

It's 2.2 microns, a near-infrared wavelength. And normally the planet is black there, very black, except for those high-altitude northern features. All of a sudden, boom, there was this bright southern feature there on the 4th of July in 2004. And we were very interested because we'd never seen anything like that before on this planet. We happened to have another two nights, a few nights later, to look at the rings of Uranus. And so, of course, the planet was there too.

But, you know, that feature had faded almost to the point of invisibility in just four nights. Wow. And what that tells us is that the atmosphere is dynamic. These are not just slow changes. There's convective activity. I mean, our best interpretation of this is that it's something like a thundercloud that's bubbling up from deep in the atmosphere, penetrating to high altitudes so that we can see it, and

then it dissipates or sinks. We can't really tell which it's doing because we just don't have a good enough spatial resolution to see that. We can see a point source that's bright there, and we know it's the planet because we can track it as the planet rotates and see it come and go. But we can't really tell is it shearing out or is it sinking. We don't really know that. But we do know that it comes and goes now with a period of just about four or five days.

Before we run out of time, let's move a little bit farther out in the solar system, out to Neptune, and talk about what's happening there. For one thing, I guess we're in on making a movie of Neptune last summer, summer of this year, that is quite a work of art.

Well, thank you very much. Eric Karkoschka at the University of Arizona and I collaborated on that. It's a movie we made using Hubble Space Telescope images, and it is available on the Space Telescope website. And what we were trying to capture in that movie is to really give people a sense of how very complex Neptune's atmosphere is. You know, I've almost given up understanding it. It was much easier to understand when we could barely detect it.

Now its atmosphere, its southern hemisphere, is just chock full of clouds. And there are so many of them that we can't barely track them and measure wind speeds. You know, years ago, even from regular ground-based telescopes, pre-adaptive optics, sometimes we could see single cloud features and track those features and measure wind speeds. The planet is far more complex today. And what is driving that complexity is something that really keeps me up at night, literally and figuratively, trying to understand what could be driving these really profound changes

in the distribution of clouds on this planet. Because, as we were saying earlier, Neptune is even further from the sun. And so what's driving that planet's atmosphere? Why is it so dynamic? It has one major difference from Uranus. It is known to have a very strong internal heat source. It's a factor of two or almost a factor of three more radiation coming out from this planet in the infrared than you would expect from its time of formation.

So it has a strong internal heat source. And perhaps it's that internal heat source that's driving these complex dynamics on the atmosphere. But what is really regulating the timescales of the change, that's something that we're only now starting to have enough data to be able to ask the question and really get answers for. And we don't have answers yet. What are you looking forward to in the next few years? I mean, obviously, Earth-based observations continue to improve, but aren't you also part of the team working on the next generation space telescope, the Webb? That's right.

Yes, I'm working very hard with the scientists and engineers who are developing the James Webb Space Telescope. That's going to be an infrared-optimized telescope. It's a different kind of telescope than Hubble. It's not really a successor or a bigger version of Hubble. It's really quite different. But it still will have very good spatial and spectral resolution that hopefully we can use to study these planets in addition to many other wonderful things in the universe.

One challenge that we're facing right now is that the current designs for the telescope don't have moving target capability, and we really need that to study moving targets. Yes. But it's a challenge because we have other priorities on this telescope. We want to see the very first light at the beginning of the universe, and so that's driving some of our design goals. So we're trying to think of clever ways, you know, we might be able to use the telescope, even if we can't get that moving target capability put in there. And we're all hoping in the end, of course, that we can get that capability, because then

that really opens up a wonderful world of opportunity for all kinds of bodies in the solar system, Kuiper belt objects, distant cometary nuclei, these planets that I love, Uranus and Neptune. Heidi, thank you so much for all of your observational work and for the great job you do communicating the excitement that you feel. I'm sure glad that you used to get carsick as a kid. Thank you so much, I guess. Well, Heidi Hamel has been our guest on Planetary Radio

today, and I hope we can have you back, too. I hope so. Thanks so much for asking me. She is a senior research scientist with the Space Science Institute in Boulder, Colorado. We talk to people from there pretty frequently. She also received the 2002 American Astronomical

Society's Division for Planetary Sciences, DPS, the Sagan Medal from DPS for outstanding communication by an active planetary scientist to the general public. And we should mention, you're a brand new board member of the Planetary Society. Yeah, and I'm delighted to serve in that role. We're happy to have you.

We'll be back with more of Planetary Radio, specifically Bruce Betts in this week's edition of What's Up after this return visit from Emily. I'm Emily Lakdawalla back with Q&A. Spacecraft cameras now use CCDs to capture high-resolution images. Before that, they used TV cameras called Viticons. What did they use before that? Film.

The Lunar Orbiter Program probably represents the most amazing use of film in planetary exploration. Each Lunar Orbiter spacecraft carried a large roll of 70 millimeter film. Both a narrow angle and a wide angle camera were configured to expose the film. Once exposed, the film was developed through what's called a bimap process. The exposed film was rolled into contact with another roll of film coded with developer. After being pressed together, the two rolls were pulled apart again. The developed film was then optically scanned on the spacecraft, and an analog signal was sent back to Earth where the images were reconstructed. Altogether, the five lunar orbiters returned photos of 99% of the surface of the moon using this film technique.

Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. We've got Bruce Betts on the line. It's time for What's Up? Yes, we're doing it by telephone again this week. Back in person next week. But Bruce, even on the phone, you can tell us about all the wonders of the night sky. I can indeed, Matt. And they are wondrous and wonderful.

There are lots of planets. All the planets you could see, you can't see. So go see them. We've got Venus low in the west just after sunset. It is starting to run away. Spectacular sight. Also, we've got Mars also in the evening, still looking bright in the east after sunset, east and south. But it is also fading away. So we've got our evening sights fading. But Saturn rising around 8 p.m. in the east. Astron Pollux, the twins of Gemini, is quite lovely and will be up high enough to do neat telescope stuff a little bit later in the evening.

And then in the predawn sky, you can see Jupiter very easily. Looking in the east, it's the really bright star-like object. And if you look below it far enough and you can see it towards the horizon, you might be able to pull out Mercury, which is up right now. Look low in the southeast in the early dawn. At some latitudes and some locations, there is an occultation of the moon. The moon, as we go around the sun, the moon ends up blocking out certain objects in the sky, and some people think it's a fun thing to go out and look at that, so it's blocking the bright star Star Speaker on December 25th.

There on Christmas, you can check on the web and find if it's doing that from your location, if such things excite you. Do they excite you, Matt? Of course they do. I wouldn't be doing this radio show otherwise. But the evening star, Venus, I noticed Sunday evening from Southern California, we had a particularly beautiful sunset from where I am in SoCal, and there was Venus, just incredibly bright and beautiful,

all by itself off a little bit to the west and the south. Just really nice. It is. Oh, actually, one more sky thing. The Quatrantids, meteor shower peaks January 3rd, 4th. There will be a pretty dark sky. This should be a pretty good meteor shower meeting, maybe 40, even up to 60 meteors per hour. Stare at the night sky, keep yourself warm, and look for bright streaks of light. And those are probably from the Quatrantids. And soon that meteor shower will be over and i will not have to try to pronounce it

anymore but in the meantime let us move on to almost all of the maria the dark areas on the moon are on the near side of the moon the side facing the earth they're basically not on the far side and uh i just wanted you to know that. I didn't know that. Does anyone have any idea why that is, why we lucked out? It was because we thought it would be prettier that way. Or someone did. Okay.

No, it's a mass distribution thing. It's in synchronous lock rotation facing one side towards us. It's more stable to line up the mass certain ways. But we still got lucky. Yeah. Makes it a more interesting object to look at. Move on to the trivia contest. We asked you, what is the world's lightest or least dense solid?

How'd we do, Matt? We did great. Lots of correct answers. Just about everybody identified that least dense solid correctly. And it is, of course, that amazing material, aerogel, which has gotten a lot of use out there beyond Earth. It has indeed. For example, it will be coming back to Earth on the Stardust spacecraft on January 15th. They used this very, very under-dense stuff to collect samples of a comet and also samples of interstellar dust. And basically the great thing about this stuff is when it hits at high speed,

these little dust particles, they can penetrate in and get stuck in there but not vaporize, which is the problem if they hit anything more dense. But it's also used for insulation. So it's actually used for insulation on the Sojourner rover on Pathfinder and for other exotic and wonderful uses. It's very weird stuff. You hold it and you can hardly even tell it's there. Yeah, I got to do that once at JPL.

It's pretty amazing stuff. Well, our winner, who did identify aerogel as the least dense solid, is Elizabeth Ambrose. Elizabeth, who lives in Omaha, Nebraska. She listens to us on KIOS 91.5 FM right there in Omaha. Elizabeth, we're going to send you out a Planetary Radio t-shirt. Thanks for playing. Congratulations. And if you'd like to win your own Planetary Radio t-shirt, answer the following question.

How big is an astronomical unit, or an AU, as we say in the business? It is the average distance of the Earth to the sun. How big is it? Get it to the, you know, somewhat accurately, but probably the nearest. So the nearest million kilometers or million miles is probably good enough. Go to planetary.org slash radio. Find out how to enter and win your fabulous prize. I want a lot of answers for this one, a lot of correct ones, everybody,

because if you've been listening to this show for longer than two or three weeks, it's been given to you, okay? So get those cards and letters. No, no, just send us email, all right? And get us that email by the 26th, Monday, December 26th, the day after Christmas, at 2 p.m. Pacific time, we'll make sure that you are up and ready to roll in this latest space trivia contest. Okay, everyone, go out there, look up in the night sky, think of how you would light your stage production of your life. Thank you, and good night.

What's that gel that's really popular? Not salmon, I forget. I'll have to look it up. I don't remember from my theater classes. But anyway, he's Bruce Betts, the director of projects for the Planetary Society. So you see your life as kind of a salmon lighting? You see the world through salmon-colored glasses? And I don't even like salmon.

He's the director of projects for the Planetary Society. He joins us every week here for What's Up. There's nothing fishy about that. Planetary Radio is produced by the Planetary Society in Pasadena, California. Back next time with our last show for 2005. Have a great week and a great holiday, everyone. Thank you.