Planetary Radio: Space Exploration, Astronomy and Science - Deep Impact: The Real Thing

Episode Date: January 10, 2005

Deep Impact: The Real ThingLearn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Deep Impact, the reality show, this week on Planetary Radio. Hi everyone, and welcome again to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. show that takes you to the final frontier. I'm Matt Kaplan. What else would you call a mission that will smack a comet with a big copper ball going 23,000 miles an hour? We'll talk with Deep Impact's principal investigator, Micah Hearn. Of course, Bruce Betts will pay us a call bringing news of what's up in the night sky and a new space trivia contest. We'll get that copper ball rolling with these headlines. Mars Exploration Rover Spirit celebrated its one-year anniversary on the Red Planet with more intriguing discoveries.

They go by the names Wishing Well and Wish Stone, a couple of rocks that are unlike any seen before on Mars. For one thing, they're full of phosphorus. You can hear what last week's guest, Steve Squires, had to say about them at planetary.org. While you're there, check out the shot Opportunity took of its own mangled heat shield. The orbiting Chandra X-ray Observatory has found what may be the biggest bang since the Big Bang itself. It snapped a picture of a supermassive black hole in the center of a distant galaxy.

The 100-million-year-old eruption from this cosmic cataclysm has the mass of about 300 million suns. And the Huygens probe is in good shape as it closes in on Titan. Next week, we'll have a complete report on its parachute descent through the thick atmosphere surrounding Saturn's biggest moon, possibly ending with shots of the surface. Deep Impact is on deck. First, though, Emily is asked if an asteroid impact could do what a terrible earthquake has done to nations surrounding the Indian Ocean. I'll be right back.

Ocean. I'll be right back. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, could a tsunami be created by an asteroid impact? How big would it be? Since 70% of the Earth is covered by water, it is much more likely than not for an asteroid impact to occur in the ocean. And yes, large impacts will certainly cause tsunami. Scientists simulated the impact of asteroid 1950 DA, which is one kilometer across and has a 0.3% chance of hitting the Earth in 800 years. The impact, if it happens, would occur in the Atlantic Ocean off of the American coast. The heat of impact would vaporize seawater, blasting out an enormous cavity 15 times the size of the asteroid and reaching down to and even below the ocean floor.

When water rushes in to fill the cavity, a ring of dozens of waves of different frequencies and speeds spreads in all directions. The entire east coast of the United States would experience waves 20 to 40 stories high within 4 hours. In 8 hours, Europe would see 3 to 5 story high waves. The disturbance to the ocean floor caused by the propagation of the waves

could make undersea landslides that cause secondary tsunamis. Fortunately, there are things we can do to prevent such a disaster. Stay tuned to Planetary Radio for more. Very few scientists devote years to a space mission that ends with the creation of a big crater, at least not on purpose. But that's exactly what Micah Hearn and the Deep Impact team are looking forward to.

The University of Maryland astronomy professor is the principal investigator for this effort to literally blow the lid off some of our solar system's oldest secrets. Mike Ahern, thanks very much for joining us on Planetary Radio. I'm glad to be with you. An exciting time, and I want to also thank you for providing what may be the most distant and exotic fireworks show for 4th of July ever. Yes, we expect to conduct a major experiment with deep impact on the 4th of July, which is actually quite different for most planetary missions that conduct either

microscopic experiments or very small-scale experiments or do passive observations. Nobody has done an active experiment on the scale we have done, we will be doing since the Apollo program when we threw lunar modules and Saturn boosters at the moon to study the seismic effects with seismometers that the astronauts had left behind. seismic effects with seismometers that the astronauts had left behind. This is the whole point of this mission, to toss this big copper ball at this comet that you've selected, Temple 1, and basically see what happens. What do you expect to see? Well, our main goal, of course, is to understand the difference between the interior and the surface so that we can use the wealth of Earth-based data

on the composition of comets to infer what the interior composition is and thus constrain our understanding of the early solar system. But what we'll actually see is very uncertain because we know so little about the structure of cometary nuclei. There is a wide range of disagreement in the research community about what will happen when we impact. Our own prediction, the team's prediction, is that we'll take about three to four minutes to excavate a crater the size of a football stadium. It could be larger than that if we have overestimated the density. It could be much smaller if a different physics is relevant to

the crater. If the comet is as strong as an ice cube, even a porous ice cube, the crater may be much smaller than we've predicted. Our own prediction is based on the assumption that strength is not important to the process because the material is so weak. So even just this measuring of the depth and the diameter of the crater that's formed is really key to this experiment. Yes, it is. The spacecraft that will remain a prudent distance from this impact, and I believe that that distance is about 500 kilometers or 300 miles,

is equipped not only to observe the impact but to analyze the ejecta. Yes, the flyby spacecraft of deep impact has about an 800-second window before it flies past the nucleus after the impact. hundred second window before it flies past the nucleus after the impact and in that time we will take a large number of near-infrared spectra to analyze the composition of the ejecta themselves and of any resultant natural out gassing from the bottom of the crater. Another unique aspect of deep impact is the importance of remote sensing from Earth, from the ground, from Earth orbit,

and from other relatively near-Earth satellites like the Spitzer Observatory. All of those facilities will be taking data because they provide a wealth of techniques that it's impossible to carry on an interplanetary spacecraft. I've also read that you won't really need a big professional astronomer's telescope to see this impact, that it may be visible with just binoculars.

Yes, even before the impact, the comet should be readily visible in a typical amateur astronomer's telescope. And the amount that it brightens is one of the big uncertainties, but it should be bright enough to be seen easily in binoculars after the impact, perhaps a few minutes when all of the ejecta become optically thin and the extra cross-section scatters sunlight that makes the comet much brighter than it was before. It conceivably could reach naked eye visibility, but binocular visibility seems quite likely. And that's, I think, a key point for our listeners, that we're not talking about light from the impact itself, but just that you're going to be spreading a lot of, what, ice crystals or water, if that ice melts, that will reflect the sunlight.

Yes, it'll be a mixture of ice crystals that will actually vaporize on timescales of minutes, timescales of minutes, but also the tiny dust particles of silicate material, as in rocks, and of organic stuff that we know are present in comets, both from remote sensing and from the previous in-situ studies of comets. Talk a little bit more about this impactor, which when I first heard about the mission, I thought was nothing more than a big, well, an 800-pound copper ball. But it turns out it also, well, you're calling it a smart impactor. Yeah, the Deep Impactor is a fully functional spacecraft. It has attitude control. It has thrusters. It has a camera that it uses to choose its own impact site with algorithms that target it for the place where it's most likely to hit in an illuminated area.

We don't want to hit on the dark side of the nucleus, for example, or in some large area that is shadowed by topography. So the impactor has been designed to avoid that and target for an illuminated area, a sunlit area. It also transmits those images back to the flyby spacecraft and from there down to Earth. And that will provide a sequence of images that is analogous to the images that were taken by the ranger spacecraft just what i was thinking yeah i was just thinking of ranger more of those active experiments and some very early ones if you look back more than 40 years ranger was i think basically a ballistic object when it hit the moon but you must be pleased that you live in a time when this spacecraft can be designed with this kind of intelligence,

because I assume that it might be difficult to do this piloting remotely from the Earth? Oh, it would certainly be impossible to do the targeting remotely from the Earth. The round-trip signal time is about 15 minutes. about 15 minutes. That is the entire time from our current last planned data analysis until we hit. So it would be impossible to turn things around in real time. It's hard enough at the moon where it's measured in seconds. Very much like the Mars Exploration Rovers.

It's that delay that means you have to have a smart spacecraft. Mike Ahern, I hope we can pause for just a second here and take a quick break and then come back and talk a little bit more about the Deep Impact mission. Mike Ahern is a professor of astronomy at the University of Maryland. He is also the principal investigator for the Deep Impact mission, which, as we speak, is about to be launched from the Kennedy Space Center off for a rather violent confrontation with Comet Tempel 1. We'll be right back. 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. Our guest this week on Planetary Radio is Micah Hearn, Professor of Astronomy at the University of Maryland. But we are talking about his role as the principal investigator for the Deep Impact Mission, which lifts off, as we're speaking, still a few days into the future, on the 12th of January 2005, headed for a major confrontation with Comet Tempel 1. Mike, let's talk a little bit more about why comets are so important to getting a better understanding of how our solar system and maybe other solar systems form. The real importance of comets is that they formed as relatively small bodies

and have not had significant heating except on their surface layers, and therefore they preserve a record of the molecules that condensed out in the early stages of the solar system. Jupiter preserves a better record of all the atoms that were present, but because of the heat when Jupiter formed, the molecular record is entirely lost, and therefore it doesn't tell us the temperature conditions in the protoplanetary disk. The comets preserve that record from the region in which they formed, which in the case of the comet we're going to was out beyond Neptune. The relative abundance of the ices that condense out there is very sensitive to the temperature at which

they condensed. So if we can pin down what the relative abundances of these ices are, we can constrain the wide range of models for the protoplanetary disk and the conditions, therefore, under which all the planets formed. So comets, by this definition, are a window, we hope, into the origins of the solar system. Indeed. We certainly have a lot of data that constrain models for the early solar system, but we don't have anything reliable yet that pins down the actual temperature in the disk, and that's one of the key things we would like to learn from Deep Impact. Why Comet Tempel 1? Was it mostly a question of that comet's orbit?

Yes. Comet Tempel 1 was chosen largely because it had a big enough nucleus to do a useful experiment, and we could deliver a spacecraft with an impactor to it with a good approach angle when it's near perihelion, when it's observable from Earth. So it was mainly a question of geometry. There's probably a good target every few years that we could go to. Comet Tempel 1 was the best one in the window we had to launch in. There are inferior targets, ones that either have a lot of dust that you have to go through or are very small or you approach from the back side. Such targets

are available probably a couple of times a year, but Tempel 1 is a very good one. We'll mention to our listeners that on the Deep Impact site hosted by the Jet Propulsion Lab, you can actually check the current location of Temple 1 and track that comet all the way to the impact planned for the 4th of July, 2005. How long have you been putting this mission together, Mike? Well, the very first attempt to put the mission together was by Mike Belton, who's now the deputy PI.

He was the PI then. by Mike Belton, who's now the deputy PI. He was the PI then. Back in 1995, the actual proposal that was selected by NASA was submitted in 1998 and selected in 1999. So it has been a long time working on the mission, but a short time compared to some of the really big missions like Galileo and Cassini. I know there are a lot of institutions involved with this, at least ten educational institutions,

ten universities, but you are from the University of Maryland, and it does sound like Maryland is taking a lead role on the science side. Yes. The University of Maryland is officially in charge of the mission through me, the entire mission. And we manage the entire science program, the education and public outreach program, and set all the requirements for the mission. The program is managed by the Jet Propulsion Laboratory, and they oversee the construction and operation of the spacecraft. They do most of the operations. The hardware was built primarily by Ball Aerospace. This is their

first deep space mission. They've got a very long track record of building outstanding instruments for Earth orbital satellites and building many Earth orbital satellites, but this is their first exploration to deep space. Where will you be on the 4th of July out at JPL? On the 4th of July, I expect to be at JPL watching the data come down. In fact, I expect the entire science team to be there, or at least the entire part of the science team that's not involved with the Earth-based observations of the impact. Well, we will certainly look forward to that, since we're in your neighborhood, and I wonder if there will be any real-time data available

over the web. We will be releasing almost real-time data. In particular, the series of images from the impactor will be released more or less as fast as we can get them converted to a suitable web format, you know, timescale. We aim for timescale of minutes, but certainly timescales of an hour are easy. And we'll release selected other images in real time as soon as we can pick out the ones that are worth seeing. Usually, you're at the University of Maryland on the 4th of July. You'll be at JPL. But right now you are in Florida waiting for this launch.

We have heard from people like Steve Squires that this is one of the most difficult parts of the mission for people on the science team because there really isn't much you can do. the science team because there really isn't much you can do. It's certainly true that there is not much I can do at this time, nor can anyone else on the science team. Although there are a few crucial things for us to do, we are still running tests of our data-taking sequences, things like that, running them on the test beds at JPL. Can't run anything on the spacecraft now. They are today, as we speak, putting the fairing around the spacecraft on top of the rocket.

So there isn't much we can do here except hope and pray that everything goes well. The rocket engineers and the spacecraft engineers are, of course, still doing functional things. Well, we will join you in those hopes and keep our fingers crossed for a great launch and a spectacular impact on Comet Tempel 1 on the 4th of July, 2005. And, Mike Ahern, I hope that we can talk to you again, either before that impact or maybe a little while after, maybe both. Okay, thank you, Matt. It's been good talking with you. And with you. Mike Ahern is a professor of astronomy at the University of Maryland and the principal investigator for the Deep Impact Mission,

lifting off from the Kennedy Space Center on the 12th of January for a seven-month trip, almost seven-month trip, to Comet Tempel 1. We'll be right back with Bruce Betts and what's up after this return visit from Emily. I'm Emily Lakdawalla back with Q&A. The tsunami caused by a major asteroid impact could be truly terrifying. However, there are actions Earth can take to prevent such a tragedy. First, we must survey the solar system with telescopes and instruments that can detect all of the potentially hazardous asteroids

and determine their orbits. Unlike earthquakes and other terrestrial disasters, asteroid impacts are entirely predictable as long as we have a complete catalog of all of the asteroids in our neighborhood. Such surveys are now underway at observatories around the world. Second, we must develop a way to deflect hazardous asteroids

away from their collision course with the Earth. This may sound far-fetched, but there are several practical proposals out there for deflecting asteroids, provided we have a couple of decades of warning at least. We could pull on the object with an asteroid tugboat, or wrap a solar sail around it to use solar pressure to nudge it out of orbit. What we need now is to build and test asteroid deflection missions so that we will be prepared to save our planet from the terrifying potential of an asteroid impact.

Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Hey, guess what? It's time for What's Up with the Director of Projects for the Planetary Society, Dr. Bruce Betts, who is, as we find him now and then, on the telephone. We have to do this by phone periodically, but it's the content that matters, right, Bruce? Oh, that's definitely true, Matt. Bruce, what have you got for us?

Well, there's a lot of exciting stuff. First of all, starting with our friends I've been talking about, but they're going away. All five naked-eye planets in the sky at one time. We won't see this again for several years, at least to see it easily. Get up in that pre-dawn sky if you possibly can. Look out there.

You'll find Venus in the east as the brightest star-like object up there. If you look just right around Venus, you'll see a dimmer object, but still looking like a bright star, which is Mercury. Mercury very close to Venus. They're both nuzzling each other for the next couple weeks, and you can find them actually on January 13th, less than 0.3 degrees apart in the sky.

Wow. Close together, kind of doing a little dance. So until the 13th, we've got Mercury above Venus, and then after the 13th, Mercury below Venus. If you look to the upper right, you can pick up Mars, which is looking dimmish and reddish and sort of smellmish. Wait a minute. Smelmish? Smelmish. Smelmish. Okay. It's a technical term. No, it's Snohomish. It's a technical term.

Oh, Snohomish. Yeah, yeah, yeah. So look for that. You'll recognize it by its Snohomishness. And then follow that line up higher, and even easier, you'll see Jupiter, which is the second brightest star-like object besides Venus. And then if you whip your head around, try not to hurt yourself, go to the other side of the sky following that same line across the sky, and you will find Saturn over in the west, just about to set, hanging out with Castor and Pollux in the western sky.

You can also pick up Saturn in the evening, finding it as it's rising right around sunset in the east, and will be directly overhead right around midnight, because it is at opposition on January 13th as well, opposition being when it is on the opposite side of Earth from the sun, and that occurs January 13th, which means it's overhead at midnight, rising around sunset, and setting around sunrise. Speaking of Saturn, the Huygens probe, lest we forget of the Cassini-Huygens mission, will be entering the Titan atmosphere. The first moon landing since we've landed on the Earth's moon in the 70s will be happening January 14th.

Huygens probe will be entering the Titan atmosphere, descending for two and a half hours before reaching the surface, and then hopefully will live a little bit after it reaches the surface. Among its instruments there is an instrument that is basically a microphone that the Planetary Society, if all goes well, we will

be processing their data and turning it into sounds, and we'll provide those sounds to you on Planetary Radio next week, as well as on our website. You can follow all of the Saturn action, all of the Cassini-Huygens action, planetary.org slash Saturn. Be there. Yeah, and right here next week, the whole show will be dedicated to

what we hope will be a very successful encounter with Titan by Huygens. So do tune in. All right, moving on this week in space history. 35 years ago, you had the first docking of two manned spacecraft, Soyuz 4 and Soyuz 5 of the Soviet Union. On to... Rebel Space Fact! Wow, how'd you do that? Well, it's a special trick, I think.

Space scientist trick, okay. Yeah, I'm getting the hang of this radio. So anyway, the actual space fact ties to those planets up in the night sky. Once Mercury drops below Venus, then we've got something going on that won't happen again for something like another 400 years. And that is that the planets will actually appear across the sky in the same order that they are from the sun. So starting from down by the eastern horizon, Mercury, Venus, and if you look down at your feet, you can see Earth,

and then look up and see Mars, Jupiter, Saturn, all five naked-eye planets in the order they appear going out from the sun. Really long time before that happens again, so if that excites you at all, go see it in the order they appear going out from the sun. Really long time before that happens again. So if that excites you at all, go see it in the next couple weeks, because Mercury and then Venus are going to be dropping away pretty soon. Extra cool. There you go. All in order, a great astronomy lesson right up in the sky.

There you go. Best place to find astronomy, by the way. Well, yeah, I suppose. On to our trivia contest. We asked you, what is the largest impact crater, the largest impact basin on the planet Mercury? How did we do? The listeners did great. Almost everybody with a correct answer.

Huge response this time around. But randomly chosen from among the correct answers was Mehdi. Mehdi Khomeili of Iran, who is a regular listener, I believe, to the show. Mehdi had the correct answer. It is the Colores Basin. Cool. That is a big puppy, by the way, and in fact was so large when it occurred that it appears to have formed some jumbly train,

a jumbly train, oddly enough, on the opposite side of the planet. Another technical term. On the opposite side? Yes, actually a jumbly terrain, jumbly also a technical term. On the opposite side of the planet, known as the antipodal point, one of my favorite planetary words, the antipodal point of the planet actually focused the impact-generated waves going through and around the planet and ended up screwing things up on the opposite side of the planet.

Man, that is a deep impact. Well, anyway, Mehdi, you're going to be getting one of those great Planetary Radio T-shirts, and Bruce is going to tell the rest of you how you can get a chance to win one next time. You, too, can win one of the Planetary Radio T-shirts by entering our contest at planetary.org slash radio. Go there and give us the answer to the following question. What was the name of the comet that the Deep Space One spacecraft flew by and took pictures of? Tell us your answer at planetary.org slash radio. And get that in to us by Monday, January 17 at noon Pacific time.

That's the deadline this time around if you'd like your chance to win one of those fabulous Planetary Radio t-shirts. Bruce, we're out of time. All right, everyone, go out there, look up in the night sky, think about what the shape of the key would be that opens the doors to your mind. Ooh, an extra helping of cosmic today. That's Bruce Betts. He's the director of projects for the Planetary Society,

and he joins us here each week with What's Up. Whoa. Come on back next time for our special coverage of the Huygens probe encounter with Saturn's mysterious moon, Titan. Have a great week.