Planetary Radio: Space Exploration, Astronomy and Science - William Hartmann on 100th Anniversary of Tunguska's Big Bang

Episode Date: June 30, 2008

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A big bang in Tunguska exactly 100 years ago, 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. June 30, 1908. It must have seemed like any other day in that thickly forested section of Siberia. Then it happened. An explosion as powerful as

a 3 to 5 megaton thermonuclear bomb. Thousands of square kilometers were flattened in an instant. Now we know it was the airburst of a meteor, even though no fragments have ever been found. Bill Hartman hasn't just thought about this, he has painted it. We'll explore the Tunguska event with the famed planetary

scientist on today's show. And stay tuned to hear what's up from Bruce Betts featuring the winner of our Random Space Fact recording contest. You're going to love it. First though, let's get another update from the Martian Arctic Circle, courtesy of Emily Lakdawalla. Emily, I was reading your account on the blog, the latest from Phoenix, and I think we've got Phoenix on the rocks. Yeah, we do, Matt. The results this week that were announced were from the Wet Chemistry Lab, part of the MECA experiment. And this is a unique experiment. They brought a little ice cube of distilled water with them from earth. They melt it, put it in a little beaker and then bring a tiny sample of Martian soil

and dump it into the beaker, stir it up and see what goes into solution in the water. And what they found was to their surprise that the Martian soil is slightly alkaline. That's the opposite of acid, but it's not very alkaline. It's not too bad, pH of eight or nine, which would be compatible with growing asparagus, turnips, or green beans, they remarked. And they found a few

metal anions and cations in this soil, and they found that the soil is only very slightly salty. So once it was dissolved in the water, they got about a few hundred parts per million of salt. And to compare that with Earth, seawater on Earth has 35,000 parts per million. So you would call this just very slightly brackish. It's not too salty. Still a little bit of trouble with those little spring-loaded doors on the TIGA instrument, I guess. That's right. TIGA continues to have little problems, but they did succeed in completing the analysis of their first sample. So that's great news for the mission. And they do believe

that they can get a sample through the barely open crack on their second set of doors. The problem with the doors appears to have been a problem in manufacturing, as far as they're saying now, which is kind of a mystery how that happened. But they're not focusing on that right now. They're focusing on how to deal with the instrument as it is, and right now they think they can work as it is on Mars. And it is a very

successful mission. Emily, thanks again. You're welcome. Emily Lakdawalla is the Science and Technology Coordinator for the Planetary Society, and she often joins us for her Q&A segment. Here's somebody else who joins us pretty often. It's Bill Nye, the science guy. I'll be right back with Bill Hartman. Hey, Bill Nye, the Planetary Guy here, Vice President of the Planetary Society. Last week, Lou Friedman, your Executive Director, and I went to Congress. We went to the Rayburn Building on Capitol Hill, which is where the House of Representatives has its offices and all its staff. And Charlie Kennel, Barry and Moore, and all its staff. And Charlie Kennel, Barry and Moore, Mary Kizza and I gave a little testimony,

a little witness to this problem of climate change. Now, these three scientists spend their days and nights studying the Earth's climate. And how do you think they do it? My friends, they use the same technology, the same style of instruments that we have been using for decades. That's NASA, the European Space Agency, the Japanese Space Agency, Indian Space Agency, Chinese Space Agency. We all use these compact, super elegant, accurate instruments to study other worlds. Well, these three scientists and I, and Lou Friedman, encourage the staffers of Congress to keep the pressure on. We need to study the Earth. The Earth's climate is changing. So we can use the same technology we use to study other worlds to study our own.

And this way we can know the amount of sunlight coming in, the amount of insolation. We can know the cloud cover. We can know the sea surface temperature, the land surface temperatures. All these data are accessible to us because our scientific instruments that we mount on spacecraft are so good. But we have to make sure we not only use these instruments to learn about the rest of the solar system, we got to make sure we learn about our own world. And this is where you, my friends, as Planetary Society members, are helping to change the world. We've got to keep an eye on our skies.

Well, thanks for listening. Bill Nye, the Planetary Guy, here. Talk to you next week on Planetary Radio. No, it wasn't antimatter. It wasn't the crash of a flying saucer either. But the truth behind the Tunguska event is almost as dramatic because it serves as a warning about all those space rocks that cross the path of our vulnerable little home world. To learn more, I called our friend Bill Hartman, senior scientist for the Planetary Science Institute in Tucson, Arizona,

though that's not where I found Bill a few days ago. Hey, Bill, it is so good to talk to you again, or maybe I should say aloha, I hear you're in Hawaii. That's right. In June each year I have a very nice invitation to come and teach at the University of Hawaii on the Hilo campus on that big island where the volcano is going off, and it's a great place to be. Fun place for somebody like you, right, who likes lots of dynamic action going on on the planet? Yeah, and it's such a planetary kind of place because there's a lot of analogs to Mars and

the Moon. We've got the craters and the lava flows. We've got geothermal energy here. We've got the observatories, of course, and the meteorology observatory that has the best set of CO2 records of the last century. So there's all kinds of interesting things going on here. You find any time to do any painting? I try to get a few days to do that, and in fact, I was out a few days ago and painted the enormous plume coming out of Holly Maumau Crater in Volcano National Park and got that painting up to the Volcano Arts Center, which is a gallery in the park that has some really nice stuff.

Well, until I make it to the Big Island, I'll have to settle for photos and paintings like yours. One of the reasons, only one of the reasons I'm so glad to talk to you on this 100th anniversary of this rather fascinating event that took place in Siberia is that you have not only studied it, but you've tried to picture it. I had a lot of fun with that. You know, as a graduate student, which was, I hate to say, way back in the 60s, my professor, who was Gerard Kuiper of Kuiper Belt fame, had edited books with collected papers, and one that was coming out just when I was a graduate student was a collection on meteorites and asteroids,

and that included papers by the Russians who had been trying to analyze eyewitness reports that people made. And you have to remember that because of the revolution in Russia, they weren't really doing science in the teens shortly after the event. So it took them about 20 years before they really had a lot of people out there to interview the eyewitnesses. out there to interview the eyewitnesses. To me, the interesting aspect of those eyewitness reports and the opportunity for me to make pictures was that those folks, you know, these were not educated people. A lot of the people who saw it, the ones who were closest, they were traders and there were reindeer herders and so on. So when they tried to describe what they saw, of course,

they had no idea what it was. And you pick up this kind of medieval language where, I remember one of the close eyewitnesses, I think this was about 40 miles from the site, the description was, the sky split in two and fire poured out from the sky. And, you know, and I say kind of medieval because there was that conception that it was sort of the dome of heavens. And then if you had a crack, you'd see through to the great supernatural cosmos or something beyond. So those are what you're dealing with. And some of them were from the cities and the towns. This thing was seen over several hundred miles, at least if you're under the track where it came in. So there were also, you know, scientific people, but mostly,

you know, non-scientific people. So taking all those descriptions, you know, that after the blast, there was a column of dark smoke came up, and it was like a spear across the sky, and I'm interpreting that as probably like the Conil, the trail, that train of debris left behind it. And I guess my point here is that today we have so many observations of fireballs and photographic materials, nothing of that scale, but we at least know what fireball phenomena are like. I had this idea a few years ago. Gee, why not go back and read those eyewitness reports again and try to put it together with what we know today and then picture what it really would have been like.

So when he says the sky split and the fire poured out, that was the moment of the big explosion. And there's a huge flash and fireball up in the sky and so on. And so I tried to do, you know, a series of paintings to show that. And we're going to put up a link, of course, at planetary.org slash radio to some of those paintings, which are on the Planetary Science Institute website. I'll tell you, they're all pretty striking, no pun intended, but there's one in particular of someone who is looking out across this beautiful forest,

and there in the distance, the explosion has just taken place, and I'm thinking this person is a few seconds away from being knocked flat. Well, you know, actually, I think that picture, there's a woman in a field on her way to school to teach school or something like that. That was probably far enough away that I think she wouldn't have been knocked down. That one was supposed to be, I think, 400 kilometers, say 300 miles, something like that. Oh, I missed that. But I have another one from, as I said, 40 miles away.

There was a trading station and there was a guy sitting on a porch, apparently facing in that direction. And he was blown clear off the porch, and I guess momentarily knocked unconscious, and the barn doors were knocked off their hinges and statements like that. So at 40 miles, people were definitely being knocked all over. were definitely being knocked all over. And at 400 miles, the picture you're talking about, what the witnesses were saying was this enormous sound. Going back through history and reading reports of fireballs, there's wonderful descriptions of the sound.

They always talk about kind of rattling sound. I've read descriptions that it sounded like a carriage driving over a bridge. It's normal acoustic sound, but it starts very high in the atmosphere and apparently reverberates around, and you get this strange, sort of like thunder, but apparently a little bit more rattling. Yeah, I read one account that said it sounded like a barrage of artillery, multiple explosions. Yeah, and you can get a sense of that when you think about lightning and thunder because the lightning flash is pow, a flash, and it's all over. And yet you wait three seconds and all of a sudden there's this rumble, rumble, rumble,

and the thunder takes a long time. And that's all the echoes and reverberations, and you kind of have some temperature layerings in the atmosphere that apparently get involved in reflecting the sound, clouds and all of that. Yeah, the sound quality is a weird thing. And, of course, in the case of the fireball, it's coming across the sky and descending through the atmosphere and probably having several smaller explosions as it comes down because, you know, it depends a little bit on the actual size of the

meteorite, and is it a stony meteorite or a iron meteorite or a very weak carbonaceous stony meteorite. Those would have different properties in terms of breaking apart as they come through the atmosphere, but you often have several explosions on the way down, so those are generating individual thunderclaps probably. I'll be right back with Bill Hartman of the Planetary Science Institute for more on the Tunguska event. This is Planetary Radio. I'm Robert Picardo.

I traveled across the galaxy as the doctor in Star Trek Voyager. Then I joined the Planetary Society to become part of the real adventure of space exploration. The Society fights for missions that unveil the secrets of the solar system. It searches for other intelligences in the universe, and it built the first solar sail. It also shares the wonder through this radio show, its website, and other exciting projects that reach around the globe. I'm proud to be part of this greatest of all voyages, and I hope you'll consider joining us.

You can learn more about the Planetary Society at our website, planetary.org slash radio, or by calling 1-800-9-WORLDS. Planetary Radio listeners who aren't yet members can join and receive a Planetary Radio t-shirt. Our nearly 100,000 members receive the internationally acclaimed Planetary Report magazine. That's planetary.org slash radio. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. We've just reached the 100th anniversary of the

Tunguska event, the explosion that leveled a huge swath of the Siberian wilderness. Scientist, author, and artist Bill Hartman of the Planetary Science Institute is fascinated by the raw power of this meteor strike. And what we're talking about is all of this damage, hundreds of square miles, was done by not an impact, but an explosion in the atmosphere. was done by not an impact but an explosion in the atmosphere. That's right. And starting in the 90s when the computer models began to get good enough, there was a paper by Chris Chiba and several coworkers, for example,

that showed that for certain sizes of objects, probably some tens of yards across, of objects, probably some tens of yards across, if it's a weak stone, which is pretty much the most common type of debris out in space, that combination, that size and that physical strength can lead to a complete explosive breakup. So the problem that everybody had, the big mystery about Tunguska, was that there's no crater there, and there's not even any meteorite fragments. That's kind of unheard of, because almost all fireballs, if they're big, will drop some pieces that you can pick up on the ground and actually look at them and say, oh, this is the kind of meteorite that produced that explosion or that train of debris across the sky. But in this case, they haven't been able to find that. that produced that explosion or that train of debris across the sky. But in this case, they haven't been able to find that.

So that was always a mystery, and that led to all kinds of not only scientific ideas but sort of pseudoscientific ideas and outlandish explanations and so on. But it now looks like if you're the right size and you're a fairly weak stony object, you could completely disintegrate in the course of several explosions coming down and one big explosion at the end above the ground. And we know that happened. I'm sure your listeners have probably heard these statements about what you actually see there today. You can apparently still see it, but certainly immediately after the impact, the trees that were at ground zero, which means directly under the explosion, those trunks of those trees were still standing. These were basically fir trees, bruises, or pine trees.

And the branches were all stripped off straight down because the force came straight down from above. And then a mile or two out from ground zero, the trees were all blown over radially, pointing away from the impact. Fascinating. I have read some work recently. In fact, we had an article by my colleague Amir Alexander on the website that we'll also link to, some work done by a couple of fellows, Mark Boslow and David Crawford at Sandia, that indicates that maybe this rock was not as big as has been thought, and that's not necessarily good news. That's right.

This is an upgrading, you might say, an updating of the computer modeling, and Sandia Labs in New Mexico are famous for very sophisticated programs modeling explosions and atmospheric phenomena, their result suggests that we basically know what the explosion was like, and we know something about how much energy it was. You assume that that's a fixed number. That's based on the observations. And then the question is how big a body caused that explosion, and their answer is somewhat smaller than the previous answer in the 90s.

As you say, maybe that's not good news. Well, why not? Well, because, well, let's think about asteroids and asteroid fragments that are out in space. The smaller they are, the more there are of them. And that's just a kind of a law of nature when asteroids collide and produce fragments. They get lots of small fragments, not so many big ones. If this explosion was caused by an object smaller than we thought before, that probably means we're going to see more of them, more frequent examples of them. And the numbers that seem to be kicked around these days are maybe one explosion of that size per one or 200 years. People used to say one per 100 years, but it may be now more like one to 200 years, something like that. And you'd say, well, gee, wait a minute, that can't be right, because I read my history books. I don't read about one of these per

century happening someplace. But you have to remember that the planet Earth has maybe something like six-sevenths of the surface covered by oceans. So six out of seven go into the drink. And so we have to wait, you know, 700 years or 1400 years, something like that, to get one over land. And then the question is, well, there's an awful lot of land like Siberia, like Antarctica, you know, like the waste of the Amazon, whatever, the Sahara, where there aren't that many people, getting one over a really dense population center in historic times, I mean, maybe that's one every few thousand years even, something like that. But still worth keeping an eye out. Oh, for sure.

And, of course, the big advance, I think, in my mind in regard to that is that we have survey programs that astronomers are running with telescopes, SpaceWatch, and other programs, trying to catalog all of the asteroids down to, we haven't got down to this size yet, but catalog all the Earth-approaching asteroids down to a kilometer, down to 500 meters or 500 yards across, something like that. We're getting down into that range. Eventually, I would guess, you know, maybe in coming decades, we may have catalogs good enough that we can say, okay, we're safe for the next 200 years, or, you know, we expect there might be a possible impact 150 years from now, not as big as Tunguska, but smaller. And we may be in a situation like that. The good thing about that is if we keep developing our human capability to operate in space as a free side benefit of that, as a bonus, you know, we would be able to fly two asteroids

that were coming in and probably deflect them. And that is a topic that we will continue to talk about on this show. Bill, as always, not nearly enough time, but I look forward to the next opportunity to talk. Great. Always fun to talk to you. Bill Hartman, good friend of Planetary Radio, is a senior scientist at the Planetary Science Institute in Tucson, Arizona. He is also an author and a painter, first recipient of the Carl Sagan Medal from the American Astronomical Society back in 1998.

And just a minor thing, he happened to figure out how we got our moon, but that's a story for another day. We've got a What's Up for this day. We're going to make that visit to Bruce Betts in just a moment. got a what's up for this day. We're going to make that visit to Bruce Betts in just a moment. You won't have to wait for another day for this week's edition of What's Up with Bruce Betts, and we're going to get to that right after this Q&A from Emily. Time once again for What's Up on Planetary Radio. We are once again with Bruce Betts, the Director of Projects for the Planetary Society,

our local astronomer for the local group, and we're going to talk about what's up in the night sky. And finally, it's only taken us a month and a half or so, the winner of our random space fact contest. Oh, very exciting. Very, very cool. So we'll come back to that. We'll come back to that. When we're ready for that.

Yeah, for random space facts. First, let's talk about the night sky, the ever so exciting Mars conjunction with Saturn on July 10th. They are coming closer and closer in the evening sky, early evening over there in the west in Leo, near Regulus, the brightest star of Leo. They're going to get very close together. And like four days before that, on July 6th, they're going to be hanging out with the moon in the sky. So it's just craziness.

Saturn, Mars, moon. It's a party. By July 10th, they'll be really close together. So right now, before July 10th, you've got Mars below Saturn. And always, Mars looking reddish and Saturn looking yellowish. And later in the evening, in the mid-evening, we've got Jupiter coming up in the east. And it's the brightest star-like object for the rest of the night. On to this week in space history.

And, of course, as people have heard earlier in the show, big 100th anniversary of the Tunguska event very exciting, very cool Big Bang Very weird Big Bang, yeah we're going to be talking more about that around the Planetary Society we care about NEOs

and trying to make sure those things don't happen again anyway, it must have been cool looking Yeah, and you've got to see some of Bill's paintings they're really nice I have seen at least many of them from the past. They're actually out there on the web. Anyway, Tunguska happened, and we'll come back to that in just a little bit. We also had in 1054 A.D.

Another big bang. Another big bang. The Crab Nebula supernova occurred. The supernova that left what we now see as the Crab Nebula through telescopes. occurred, the supernova that left what we now see as the Crab Nebula through telescopes. Which I happen to know Neil deGrasse Tyson says is noted in almost every culture around the world except Western Europe, where they must have seen it, but it didn't fit their image of the cosmos, so they just ignored it. This big thing you can see in daytime. Or maybe it was just

cloudy. Yeah, maybe it was a cloudy day that day. I don't know. Those days. Especially Northern Europe. Maybe they were too busy shooting at each other with bows and arrows. Yes, yes. Anyway, I think it's time to go on to that other thing. So how would you like to handle that? Oh, are you ready? I'm ready.

Okay. Ladies and gentlemen, from Brandon Cook of Indianapolis, Indiana, his take on a random space fact. Random space facts. Random space facts. Random space facts. Random space facts. Random space facts.

Random space facts. Random space facts. Random space facts. Random space facts. Random Space Facts. Random Space Facts. Random Space Facts. Random Space Facts. So, pretty cool. We can excuse him for making it plural, right? Oh, yeah. Yeah.

No, that was very cool. Isn't it great? It's very talented. So, are we going to give him something? We've got to give him a shirt. I think we said a shirt to whoever enters. Okay. All right. Congratulations. Brandon, you got a cool. Isn't it great? It's very talented. It is. So are we going to give them something? We've got to give them a shirt. I think we said a shirt to whoever enters. Okay. All right. Congratulations.

Brandon, you got a shirt. Good job. Very nice. I feel threatened, but very nice. No, don't worry. You're safe. Well, to talk more about Tunguska, because I can't get enough of it, the size, did you know, equivalent to, and the number's a little imprecise but three to five three to ten megatons

of tnt that's a really huge nuclear weapon uh yield and something like 500 times larger than the uh 15 kilotons that hiroshima was big so big ugly leveled 2 000 square kilometers of forest and ruined a couple of reindeer card games. So I hear. Talk about reindeer games. All right, moving right along, we go to trivia. And we had asked you, star in the sky that has the largest proper motion. In other words, kind of moving sideways across the sky as we see it,

as opposed to just receding away from us, as many of them are. But many stars are not going directly away from us. And what's the answer? How do we do? John Doyle. Congratulations, John. I listened to your show for the very first time and thoroughly enjoyed the piece on Titan, said John. And he got it right.

Barnard's star. So, John, you must not have been expecting to win on your first tryout because you didn't give us your shirt size or where you live. But we're going to get that from you. At least I hope we are. And we will send you a Planetary Radio t-shirt. Indeed. Do you know what else I learned from listeners about this? Do you have some random space facts?

I do, actually. Got it in. Thank you. Yeah, it's in the contract. You had to do it at least once per show. I did. And this probably is in. Thank you. Yeah, it's in the contract. You had to do it at least once per show. I did. And this probably is facts, so go for it. Barnard's star is, first of all, it was discovered in 1916 by pure coincidence, E.E. Barnard.

No way. Isn't that incredible? That's bizarre. What are the chances? Barnard's star is, in about 10,000 years, going to be the closest star to our solar system. It will be closer than Proxima Centauri. It's coming our way. Wow.

You have a wealth of... I really feel threatened on this show. Thank the listeners. Oh, they're cool. They give us all sorts of good information on these things. And let me give them a chance to give us more information. How about that? Talk about stars again.

Brightest star in the sky is Sirius, the dog star. And Vega, also a very bright star. For this time around, tell me what are the brightnesses of those stars measured in magnitudes, the astronomical unit of brightness measurement, the strange logarithmic scale. What's the brightness of both Sirius and Vega to be entered in our fabulous random competition? How do they enter? For correct answers. I'd go to planetary.org slash radio and find out how to enter if you don't know already.

And get that entry to us by 2 p.m. Pacific time on Monday, July 7, so that you can have a shot at... We did it again. We didn't talk about what to give away. Do we have a poster or something we can give people? Sure. Let's give them an explorer's guide to Mars. Cool.

Let's do that. Give you a lovely map of the surface of Mars with wonderful factual content all around it. And you know what? Next week, we're going to have another special prize having to do with the movie WALL-E, because we're going to talk about that a little bit. WALL-E. Have you seen it already? No, you couldn't have.

No, I'm not. It's more like WALL-E. Sounds like an asthm. WALL-E. Have you seen it already? No, you couldn't have. No, I'm not. It's more like WALL-E. Sounds like an asthmatic WALL-E. It's a great movie. It's a great movie. And we're going to talk a little bit about it next week and what it has to do with NASA. I look forward to that.

All right, everybody, go out there, look up at the night sky and think about really big bangs. Really big bangs. Really big bangs! Boom! You could be a Foley artist. I always thought that would be fun. Well, it's a shame the video camera wasn't running just then

so that we could watch. Dr. Bruce Betts, the Director of Projects of the Planetary Society, who joins us every week here for What's Up. Next time, a little robot named Wally and some of his real-world ancestors. Planetary Radio is produced by the Planetary Society in Pasadena, California. Have a great week. Редактор субтитров А.Семкин Корректор А.Егорова