Planetary Radio: Space Exploration, Astronomy and Science - Stardust Status Report

Episode Date: February 16, 2004

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Star Dust is returning to Earth, and wouldn't Hoagy Carmichael be proud? This is Planetary Radio. Welcome to our show. I'm Matt Kaplan. The magic continues on the Red Planet with two, count them, two rovers making daily discoveries. But we're taking a brief break from Mars on this week's show, except for hearing from two Mars student astronauts. Stay with us for an update on the Stardust mission from Principal Investigator Don Brownlee. And Bruce Betts is out of protective quarantine.

Back in a minute. Hi, I'm David Torsi. I'm just past 16 years old. I'm from Hungary. I'm now on the final day of my student astronaut program. And it's been very nice wonderful to be here fun and the most interesting were the meetings where we had a chance to see how decisions about the mars exploration rovers are being made and i could talk to a lot of scientists and they were all nice and they answered when we asked when i go go back, I guess I'll have to keep on with the interviews. I had quite a few of them before I left, so I think I will have them after I arrive back.

I think my friends will be very interested in my stories. I collected many of them just for fun. I hope I can keep in touch with the people I got to know here because it would be very nice to continue this whole program. Astronomer Don Brownlee is the principal investigator for the Stardust Cometary Sample Return Mission. In a nearly cosmic coincidence, Stardust had its dangerous encounter with Vilt-2 within hours of Mars Exploration Rover Spirits landing on Mars.

Now, a month and a half later, and with Stardust on its way back to Earth, we knew it was time to get a status report. Don is usually at the University of Washington, but he was enjoying a very different academic climate when we spoke. Dr. Brownlee, we find you not in rainy Washington, but in rainy Hawaii. What are you doing at the University of Hawaii? Well, I'm on sabbatical this quarter, and last quarter I was on sabbatical in Arizona, and this quarter I'm on sabbatical in quarter, and last quarter I was on sabbatical in Arizona, and this quarter I'm on sabbatical in Hawaii.

Two warm but quite different places. Nice place to be, but still getting some work done there, I take it. Oh, yeah, working hard. Let's talk about Stardust, of course. What's the current status of the spacecraft? The spacecraft is in excellent shape. After the flyby, which we have a lot of exciting data for, shape. After the flyby, which we had a lot of exciting data for, we closed up the collector,

which returned to Earth on January 15th, two years from now, and locked it shut. And so the sample is ready to come back. We did a trajectory correction maneuver just a couple days ago, and that went fine. And everything is great. We're still doing some things. We're testing out the solar cells to make sure that the solar cells weren't degraded at all during the encounter. But as far as we can tell now, everything worked fine. The only thing that was affected by the flyby, interestingly enough, was the mirror the camera looks through. The camera that took the images of the nucleus on approach looked through a periscope. And it did this because we were worried about rocks and dust from the comet coming in at six kilometers per second, fly-by-speed, cratering into the front of the camera lens. So we

looked through a mirror during approach, and then we were close, and the camera would scan off this periscope, and so it was protected by itself. It turns out that was a good idea. After the flyby, we took images through the periscope of stars and compared those pictures of stars from before the encounter, and it was quite different. So the mirror was damaged. It has no effect on us. We lost the mission.

We don't need it again. So it did exactly what it was supposed to do. Absolutely, yeah. And it's very interesting. The European mission that went to Common Halley in 1986 actually lost its camera during the encounter. It was hit by some bad things from Common Alley and never functioned again. Well, your spacecraft, Stardust, has fascinated me and a lot of other people for many reasons, but partly because you had to develop and implement so many interesting technologies.

And maybe we should talk a little bit more about that before we get to some of your results because even even before that uh return of uh samples to earth uh stardust has already returned an enormous amount of data you had these uh the whipple shields the the aerogel collector there was so much going on up there and you say that really everything worked uh exactly as planned i i hear that there were a few particles that got through the first layer of some of your so-called Whipple shields. Yeah, the spacecraft is protected by a Whipple shield named after Fred Whipple, the Harvard-Smithsonian scientist who actually invented this shield in the 1950s, believe it or not.

But the Whipple shield or Whipple Bumper consists of a front plate and then a space or spaces behind it and then another plate. And the idea is that particles that are coming in extremely high speed, when they hit the front plate, which in our case was a little graphite honeycomb about a centimeter thick, but it's made out of very thin sort of eggshell-type materials. When the particle goes through that front plate, they actually break up into large numbers of fragments and vapor, and then those fragments then expand out.

So when they hit the other layers, they're covering a lot more area and are stopped. It's kind of interesting. You can imagine if you held a thin piece of, say, aluminum plate in front of you and someone shot at you with a rifle, the bullet would go right through the aluminum and right through you. but if someone shot a bullet that went five or ten times faster than a normal bullet, which is sort of typical meteorite speeds, then the bullet would have so much kinetic energy. When it hit this aluminum sheet you were holding in front of you, it would go through it, but it wouldn't come through it as a solid object. It would break into all these little fragments, which explode and then hit you.

It wouldn't feel good, but you likely would survive. And this is the concept of a Whipple bumper, a meteor bumper. It breaks up really high-speed particles and spreads out the damage over a larger region on the downstream parts of the spacecraft. I would think that this, what amounted to a proof of concept for Whipple shields on Stardust, would have applications for many other spacecraft that have no plans to go anywhere near a comet. Yeah, the space station has shielding on some parts. The Giotto spacecraft that flew to Comet Halley had a Whipple bumper on the front.

It's a different design than ours, but the basic concept is the same. And the Deep Impact mission, which will be launched to a comet this year, also has a partial Whipple shield. Our shield was fairly elaborate because we had to go close to the comet to collect particles, and so we always had this interesting balance. We wanted to get close enough to collect a lot of small particles, but then we wanted to be able to survive the impact of large particles. So comets put out little dust particles that we want the size we want to collect,

say tens of microns in size, you know, human hair and smaller in size and diameter. But it also puts out rocks in the centimeter to meter size. The bigger ones are rarer, but they're deadly. So our Whipple shield was designed to protect the spacecraft from the impact of particles up to about a centimeter in size. about a centimeter in size. The indications are from the dust counters we had on board that at least a half a dozen particles actually penetrated through the first layer of the Whipple shield. So the way we detected this, we have this honeycomb, and then there's a space of a couple inches,

and then there's a fabric sheet, and we put a microphone on that fabric sheet and so when you get a hit on the microphone on on that sheet behind it tells you that something basically came through the door yeah and that was alarming because I thought it would have been interesting to have maybe one impact through the the front shield just to make things interesting. But I would have never been happy to have half a dozen or possibly more. And not all the front is incident. So we probably had at least a dozen or two particles that went actually through that front shield. So a dozen or so of these deep impacts, if you'll pardon the expression.

But you have an idea of how many particles impacted the spacecraft altogether, I think. Yeah. You know, there's a size distribution of particles. There are many, many small ones and fewer and fewer big ones. And our goal was to collect 500 particles larger than 15 microns in diameter. And indications now are that we did just do that or exceed it a little bit. But altogether, there were millions of particles that hit the spacecraft, down to the smallest sizes.

Our guest on Planetary Radio this week is Dr. Don Brownlee. He is the principal investigator for the Stardust mission, which on January 2nd made that amazing flybyby really almost a fly-through of a comet, at least a fly-through of the tail, and has lived to tell the tale and is on its way back to Earth. We'll talk a little bit about those particles that it's about to return to Earth and some of the other amazing results from Stardust right after this quick break. 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. You can learn about these adventures and exciting new discoveries from space exploration in the Planetary Report. The Planetary Report is the Society's full-color magazine. It's just one of many member benefits.

You can learn more by calling 1-877-PLANETS. That's toll-free, 1-877-752-6387. And you can catch up on space exploration news and developments at our exciting and informative website, PlanetarySociety.org. The Planetary Society, exploring new worlds. Planetary Radio continues with our special guest this week. He is Dr. Don Brownlee, the principal investigator for the Stardust comet mission on its way back to Earth now, laden with a few thousand or more particles from that comet,

which, Don, we've been calling Wild 2, but to be more precise, it would be pronounced Vilt 2? Yeah, it was discovered by Paul Vilt. And we want to be fair to him, so we'll try and remember that from now on. What has most surprised you about the results that you've already been able to get back from Stardust? Well, the most surprising thing is how feature-rich the surface of the comet is. You know, we didn't really know what to expect. The two comets that have been imaged before with spacecraft so you can actually see some surface details

are Comet Halley, which is about two or three times bigger than built to, and also Comet Borelli, which was imaged a couple of years ago by the DSpace-1 mission. Both of those comets were interesting, but they didn't show very many surface features. They kind of looked in a way like asteroids. Our comet here is really astounding. It's about 4.5 kilometers in diameter, and it has these huge depressions that actually cover the entire object. It's like you took a bunch of clay and stuck your thumb into it.

It plays all around, so it's covered with depressions. Some are really quite deep and cavernous. It's really remarkable. In evaluating these, we've been quite amazed. For one thing, we found impact craters. There are definitely high-velocity impact craters. So when you see a body that's four kilometers in diameter and it has large impact craters on it, it means it

has to be extremely old. We know the comet's old, but we didn't expect the surface to be old because comets, you know, when you see them and they have tails and shooting gas and dust off into space, they're actually coming apart. Unlike asteroids and planets, when comets are active and in the inner solar system, they're literally coming apart. Every time they go around the sun, they lose on the order of a tenth of a percent of their total mass. Typically, when you expect to see a comet, you expect its ancient surface to have been gone by this erosional process. And yet we do see some ancient

surface, and yet we also see recent features. We can see dozens and dozens of jets of gas and dust jetting out from the surface at supersonic speeds out into space. So this thing is coming apart. We can actually see it coming apart. That is just an amazing photo, by the way,

which people should check out, either on the Stardust website or the Planetary Society website, that photo where you can literally see these jets emerging from the surface of the nucleus. Yeah, we'll have much better ones released in the coming months. It's really stunning. So the really exciting thing about this is that we caught a comet in an interesting stage of evolution. So it

has features on it that relate to things that happened recently. I mean, this comet has only been trapped in its present orbit going basically from the orbit of Mars to the orbit of Jupiter for 30 years. Brand new, at least for this time in that orbit. So we do see new surface features related to that history

and things that have happened, say, in the last million years. But we also see features that clearly were made a long time ago, presumably billions of years ago, when it was orbiting out in what's called the Kuiper Belt, the region of space around Pluto, actually, at the very, very edge of our planetary system. So it's really exciting. So we have information from something that was exposed for billions of years

at the very edge of the solar system, beyond Neptune, where Pluto is, and then active features that have come in. So this is exciting not only because it's a body, but it's actually a comet. I mean, comets were intimately involved in delivering at least some of the water that's on Earth and at least some of the carbon organic materials that were delivered to Earth and needed for the development of life. I mean, there are carbon atoms in our bodies that were formerly in comets. Water and carbon, important stuff.

And this fact that comets are so ancient and, at least in part, quite pristine, is very much one of the justifications for studying these bodies. What else might we be able to learn from this data from Stardust, even before that sample is returned a couple of years from now? And we'll talk about that sample in a moment. Well, we're primarily studying the surface of the comet to provide real direct information about how comets work. There's been a lot of speculation.

Normally a comet, what people call a comet, is something they see in a telescope. So they see a great tail, they see a comet, they see all this stuff coming out. But that's not really the comet. That's the comet coming apart. That's the pieces of the comet that have been released into space. The comet body is an unknown thing. So there's great speculation. What causes that tail when it comes in close to the sun, what causes the source of all this gas and molecules. So now we have a first really up-close, precision look at one of these things.

And so now we can look at all these ideas on how these things work and compare them to what we really see on the surface. It's really quite stunning. For instance, we see a surface that looks reasonably strong. At least it's not a powder. I mean, we actually see some overhanging cliffs on this thing. So the gravity is very low. But nonetheless, the surface cannot be a simple powdery material. It has to be a reasonably cohesive material.

All of this, by the way, is quite of interest to people involved with the Deep Impact mission, which is going to be launched this year and is going to a comet and actually going to have a probe smashed into the surface of a comet. So they're extremely interested to know what the surface of one of these things actually looks like. And the Europeans are also launching a mission called Rosetta, which in about a little over half a decade will actually orbit a comet and drop a little landing package on the surface. Lots to look forward to.

And with just a couple of minutes left, let's talk about the next extremely exciting event in the life of Stardust, one I'm sure you're looking forward to, which is recovering that sample package from somewhere out in the desert, right? Yeah, the capsule returns with the samples. It's coming back in Utah in the beginning of 2006. And this is really an exciting thing and is the primary reason for having the mission. The pictures and so forth are just sort of a plus on it.

But the real goal is to get cometary dust particles that were coming out of the comet and freshly liberated along with ice. And the reason we're so interested in these is that these are preserved building blocks of our solar system. So our sun, our planet, our earth, and ourselves were made out of materials that are actually still preserved in these ancient comets that formed four and a half billion years ago at the very edge

of our solar system and preserved at really incredibly low temperatures for basically all this time. And we see all these surface features that are interesting, but those are modifications of the surface on a large scale. The actual building blocks of comets, we believe, are beautifully preserved. And we need them back in our lab because we have to study them. To get the records, we have to study them at basically the nanoscale.

It's like modern electronics. The information is stored at the tiniest possible scale. So we need things like electron microscopes and mass spectrometers to really get at the secrets really buried in the cometary material. And it will be a little bit of space history being made as well. There are not too many sample return missions in the history of space exploration. We were the first sample return launch since 1972, with Apollo 17. So it's really exciting. But there's also another sample return mission that was launched after us,

and it's coming back next year. It's not to a body, but it's just going out into space and collecting particles from the sun, solar wind. It's called the Genesis Project. It will be coming back to Earth next year in the same place we're coming back. So it's kind of like a training ground for our recovery. We hope they do well. A lot of the same team members are involved in the design of the returns for both Genesis

and Stardust. But no, it's a great, exciting thing. And there are a lot of things that you can only really do with return samples. You hear a lot about rovers on Mars and stuff. You can do a lot with that. But if you want to get to the real nitty-gritty of materials, you have to have them in the lab where you use instruments with sometimes way thousands of tons in the biggest shopping center, quite literally. Don Brownlee, we're out of time.

I look forward to being able to check in on the health and status of Stardust again during this mission and certainly very much look forward to two years from now with those sample returns. But it sounds like there will be much more happening before then. You mentioned some even better photos becoming available in the next few months. I want to mention that we will have your website, the Stardust Mission website, on the webpage where people access this radio program at planetary.org or planetary.org slash radio. And I also want to credit Amir Alexander, a colleague at the Planetary Society, who's written a couple of excellent articles on the Stardust Mission and results to date,

which are also available in our news archives at planetary.org. Don Brownlee, we'll let you get to your reception there at the University of Hawaii, and I hope we can talk to you again soon. Thank you. Thank you very much, and aloha. And Planetary Radio will return with Bruce Betts right after this visit with a student astronaut. Hi, I'm Sathvik. I'm 14 years of age and I'm from India. Well, I've had lots of fun being a student astronaut. It's really interesting how we get to interact with scientists, ask them whatever we want to know.

And what's really amazing is that they, you the time for us, no matter what they're doing. They just explain everything to us. So it's been amazing seeing how scientists work and they just collaborate on everything. They have discussions but they don't turn into arguments. I bet that's really hard. Both of my friends are pretty happy, they're excited too, so I'm sure they want to know everything, you know, a blow-by-blow account. I already got a lot of media attention, so probably

I'll get a bit more. I wanted to be an astronaut, but maybe, you know, I could be a scientist or an engineer. Well, I think that if they really want to do something, then they should just go ahead and do it, and if they work really hard at it, it will happen for them, too. We have reached that point in the show when we will talk once again with Bruce Betts about what's up. And on this President's Day holiday, Bruce is up. He's up in the Sierras, the high Sierras, or at least what, the foothills, Bruce? The foothills of the Sierra, Matt, in gold country. One of my favorite places, up near that area, Angels Camp, where Mark Twain wrote his great jumping frog story.

Yes, yes, the place is just nasty with frogs. It's like a plague in the Bible. That's not actually true, by the way. I hear that you've actually entered the competition for jumping frogs. Yeah, a long time ago in college, our student radio station, we actually had a frog in the contest. I think that the Planetary Society should do the same, don't you? I do, I do indeed. And in honor of today's guest, we should name it Comet. Yes, I think so, absolutely.

Or Vilt. Vilt. We have something else we do also have to talk about, and that is that Biff and Sandy have not joined us this week. What happened? We thought they were going to be here. Well, rest assured, they will be back next week's show, but we had some issues with the communications.

They all exist, but apparently Biff tripped over something and messed up something called flash memory, apparently, on board spirit. Caused a few issues. We'd rather not go into all of them. The point is we will have those correspondence coming down, and we will have them on the show next week. So join us for more Biff Starling and Sandy Moondust, first astrobots on Mars. In the meantime, you can read their stories at planetary.org.

Certainly does explain a lot, doesn't it? Well, Bruce, what's up this week? Well, look up in the night sky, see fun planets. Venus is that incredibly bright thing in the evening, and you can look above it to its upper left a ways and see a much dimmer, orangish-looking Mars. We've also got Saturn high in the night sky, beautiful to look at, including with telescopes. Jupiter rising somewhere around 730-ish up for the rest of the night into the pre-dawn

will be the really, really bright thing before dawn. And don't forget, if you do have a telescope, go out there, take a look at Jupiter, especially Jupiter and Saturn, with Saturn with its stunning rings and also can probably see at least its largest moon, Titan. And Jupiter with its four very large moons, the Galilean satellites. You can see them as little points of light looking like little stars that move from one night to the next, next to Jupiter. That was almost lyrical. What else do you have for us?

Well, we've also got some random space bugs! The average frog can... Wait, no, that's not space bugs. That's one small leap for a frog. One giant leap for amphibians everywhere. No, no, no. Mercury. Mercury is the topic.

Turns out that we've only seen half of Mercury. That was from Mariner 10, at least up close and personal. Half a planet, essentially unexplored. That will be rectified in the coming years with the Messenger mission and also a European Space Agency mission, BepiColombo. And we look forward to seeing more Mercury. In the meantime, we're going to go to our trivia contest. Last week we asked you what was the last Apollo

mission, last Apollo crew to have to go into quarantine after returning to Earth to make sure they didn't carry any nasty moon bugs that would plague humanity. What were those answers out there, Matt? Bruce, we got a number of different answers. Of course, only one was right. The sad thing is that we had some new people that we hadn't heard from before, but they did not give us the correct answer. And the correct answer was, according to your research, Bruce? Apollo 14. So we go to a listener who has won in the past,

who submitted the winning answer that was randomly chosen this week, Paul Boucher of West Lafayette, Indiana. Paul, congratulations. You just need to let us know what size shirt you want, and of course that'll be a beautiful and form-fitting Planetary Radio t-shirt. I would love to say that I have one on now, but the FCC doesn't like that kind of lie. It's hanging across from me as we talk about this, but I'll put it on later in your honor, Paul. Hundreds of miles away, I actually do have mine on right now, even as we speak. And it's so cool, because people come up to you and they say,

what the hell is that anyway? And then you can tell them. Oh, I just have our fans come up to me and say, oh my gosh, are you associated with Planetary Radio? So you too can have this by winning our trivia contest. Yay! And speaking of which, trivia contest for this coming week. We're going to stick with Apollo 14. I usually try to bounce around, but I'm inspired this week to stay with Apollo 14. The answer for last week on Apollo 14, there was perhaps the most famous golf shot in history by Alan Shepard, who hit a couple of golf balls on the moon.

My question for you is, what type of golf club, or actually just the head, was he using? Not what brand, but what type, what number? So Big Bertha would not be right. We're not looking for the brand. We're looking for, was it an iron, a wood, and a number, right? That is what we're looking for, and that could win you a Planetary Radio t-shirt. If you go to planetary.org slash radio and enter our contest. And please try to do that by Thursday noon Pacific time, this coming Thursday,

so that you'll get in and be considered for the contest. We'll reveal the winner a week from today, Monday. And, Bruce, we're out of time. You probably want to get back to enjoying a really beautiful place. I do. It's a beautiful place with all sorts of animals in addition to frogs and fun stuff. Pretty skies? No, but pretty surroundings.

Oh. Okay. You just have an inherent sense for the weather around the world, don't you, Matt? I do, but nevertheless, Bruce... Go out there, look up in the night sky, and try to find something that looks like a junking frog, or a jumping frog, whichever you want. Thank you, and good night.

Bruce Betts normally comes to us from a little closer to home for What's Up, this regular segment at the end of each edition of Planetary Radio. He is the director of projects for the Planetary Society. Ribbit. Thanks very much for listening. Back with a new show next Monday. Be sure to join us. you