 Good afternoon. Welcome to our daily comet update for Friday, July 21st. What you're looking at now is a boom from a plume, and we'll have more on that later, and as well as some other images from Jupiter, including the double whammy impacts of Fragments Q&R. As just a schedule note, though, as a reminder, tomorrow at 11 a.m., we will have our closing briefing of the comet impact series, and that's Eastern Time. What's expected is a dramatic plume from Fragment W's impact, and a look at changes we're already seeing at the impact sites, and how the impacts of Comet Shoemaker-Levy 9 have lived up to predictions, and joining us tomorrow in addition to our regular panelists will be Heidi Hamill of MIT and Melissa McGrath of the Space Telescope Institute. So let's move on to our panel today. With us here to my left is Dr. Robert West, a scientist from the Jet Propulsion Laboratory and a leader of the team using the Wide Field Planetary Camera 2 to see what the dust from the comets is doing to Jupiter's atmosphere. To his left, Dr. Andrew Ingersoll, a scientist from Caltech and a member of the Wide Field and Planetary Camera 2 team, and will tell us about the booms and plumes on Jupiter resulting from the G Fragment impact. And back for yet another day, Dr. Eugene Shoemaker, a long-time comet watcher and co-discoverer of the Comet Shoemaker-Levy 9 and an astronomer with a Lowell Observatory and with the U.S. Geological Survey. To his left, excuse me, to his left Dr. Lucy McFadden, University of Maryland and University of California, coordinator of the Worldwide Comet Observing Campaign and a visiting professor at the University of Maryland. And to her left, David Levy, co-discoverer of the Comet and also an author and a popular speaker on astronomy. And at this point, I'd like to turn the program over to Eugene Shoemaker. Thanks, Don. Well, the status now is that all the fragments that we could see at the telescope have hit Jupiter, so that part of the show is over, although I'll remind you that there's still the following wing coming in, so we may not have seen all of the impact events. Probably the most interesting observations right now are going to be presented by Bob West and his look at two fragments that happened at very nearly the same site. Bob? We have the first image. What I'll be showing in the first image is a true-color picture of the way Jupiter looked soon after the fragment R hit Jupiter. And the great red spot is clearly visible in this image as well. Now, I'll walk you through what we're seeing here. You can see the familiar 45-degree south latitude. And on the very right edge of the planet, passing over the limb, is the remains of the impact from fragment L. That happens to be a fairly big region that L is covering. Then the next to the blow and to the left of the great red spot, there's a dark area that is the remains of what we saw from the G and D impacts. Originally, we saw them very well distinctly separated, but here we see a much more complex region they seem to be moving together and evolving. Then to the left of those, there's a very dark spot, a little bit left of the central meridian of Jupiter, the central longitude. That dark spot is a new one. That's the R impact. And it's not as close as we might have expected at first to the other ones, but there it is. Then to the left of that is the impact from Q1. And further over is the impact from H, which is also a very large spot. Very careful inspection of these images also shows some much smaller features. We can see the B feature in here and the N feature. And I've seen a more recent image which we didn't have time to prepare for this, but it also shows the S impact region which is about halfway between R and DG complex. The S looks very much like R does. Now the R and S sites are not as large as some of the other ones. They're kind of in the medium range. We see much smaller impact events and we see much larger ones. I want you to carefully look at this image, just take a mental note of the size of what we're seeing. We're seeing the core dark regions here mostly. You can barely see away from these some faint, darkish patches, which show regions where we have ejecta dust material that spread widely but thinly over the planet. Now these visible images are nice to look at, but we're learning a lot more from other wavelengths that we can't see, like the ultraviolet and the infrared. And I'll show you the next image is one taken in the ultraviolet. This is in the near ultraviolet, a little bit short word of where the visible atmosphere blocks sunlight coming into the Earth's atmosphere. This is at 2550 angstroms for those of you who know what that means. But what I want to show you here is these very large sites that we can see in the ultraviolet. You see two of them. I think it's L on the right and again D and G closer to the center, which are very large regions covered very widely by mostly what we're seeing here is dark absorbing dust, which shows up very well in the ultraviolet. We also see a lot of other features in this image and I'd like to move on to the next one, which shows now all the features that we see just in this one image. I also want to remark here that there is a circular black feature to the north of Jupiter's center. That's Jupiter's moon Io, which is also very dark in the ultraviolet. Here we see it in front of Jupiter. So here we can see on the right the huge feature from L, D and G, R, Q2, Q1, I was right first, Q2 then Q1 moving towards the left, N, B and H is just coming on the left. Some of these smaller features are too small to see in this televised version, but we can see them when we look closely at the images. Now, I think this is significant in terms of what we're able to see in Jupiter's stratosphere. These big black splotches are not holes in the clouds, they're not waves, they're mostly dark particles and also some UV-absorbing gases that appear on Jupiter's atmosphere. The significant part is that we're seeing them high in the atmosphere and the stratosphere. This is the first time we've ever had markings like this in the stratosphere and we can use these clouds to trace the winds and to measure the circulation of the stratosphere. So it's going to be very important for Jupiter science and this is just the beginning. We're just now starting to examine some of the motions that we see and we have more observations coming up all the way into August which will tell us a great deal of information about the stratospheric circulation. So we have a lot coming in the long term that we also have a lot of exciting results in the near term and at this point I'd like to turn it over to Andy Ingersoll or actually back to Eugene. Well, I will turn it over to Andy then. We're going to hear about the boom. I'd rather call it just a very low frequency sound wave. I hope people will not think of this as a sonic boom. The sonic boom was a shock wave and that's not what Andy's going to tell us about. Right. Just think perhaps of a flash of lightning. A little while later you hear the sound from the thunder and if you were on Jupiter you would hear some sound from these explosions. You hear a huge sound wave if you're close but if you're farther away it would take some time to get to you and in fact it propagates at the speed of sound and we know something about the speed of sound in Jupiter's atmosphere. It actually depends on whether the sound is traveling in the stratosphere or at deeper levels and so we hope to use the information about the measured speed of sound from these waves to tell us where the wave is traveling, whether it's traveling in the stratosphere or down deeper. Let's show the familiar, by now familiar, G-impact site. Some of you have studied this and you can see sort of to the southeast a big horseshoe shaped pile of material which is probably the ejecta that was flung out into space and then fell down onto the atmosphere. Inside that there's a little elliptical region that I want to talk about and of course off to the northwest is the D-impact site from an earlier fragment. So let's see the next. This is what the G-impact site would look like if you were directly above it. You can see that circle, that prominent circle is indeed circular which is what you get from a wave spreading outward from a single explosion. Now this picture was taken about an hour and a half after the impact and the radius of that circle is about 4,000 kilometers and you can compute how fast that wave is going. It's about 800 meters per second which is the speed of sound of hydrogen gas in the stratosphere of Jupiter. That speed also matches another kind of stratospheric wave, a gravity wave but either way it's a wave in the stratosphere. Now if you study that image very carefully inside that prominent circle there's an even smaller circle, very faint and you might and we do suspect that that's a wave deeper down that's giving us some indication of its existence and we can tell that it's deeper down because it's propagating slower. The inference from all this is that this comet has excited a stratospheric wave much more than it has excited a wave deeper down and that suggests that the comet has lost most of its energy high up in the atmosphere and not down deep. I've also got a video of this just to convince you that this wave is indeed expanding outwards. We've got a series of images in different filters the time step is three to five minutes between filters and we can use it as a little movie that over this very brief span of time in a sequence designed to look for color we can use it instead to look for time dependence. Now maybe we'll see it a little faster and I think you can see that wave is spreading outwards. A little problem with the alignment there and this is the sort of thing we want to do with images in our future analysis in order to figure out some of the properties of Jupiter's atmosphere especially at the levels that we can't see and decide where the comet deposited its energy. I also have some measurements of the prune velocities. We can look at sort of a cross section of Jupiter's atmosphere. This shows you the different cloud layers in the next video. The different cloud layers down at the bottom. In fact, the clouds of Jupiter are rather thin. Those three parallel bands at the bottom are only 100 kilometers thick. At the bottom is the water cloud and I've shown the comet going through that water cloud. That's actually controversial. In fact, I don't believe it anymore. I think in fact the comet did not go through the water cloud. Above that is the cloud containing sulfur in the form of ammonium hydrosulfide and then above that is the ammonia cloud which blocks our vision from space normally. And then the comet came in from left to right. That's from south to north in this image and then rebounded back out along the path it went in and set up this huge plume. Now, if you look at that picture, I've got one line labeled visible from Earth. That's because Earth is over the horizon and so you can't see the ground from Earth or you can't see the cloud deck at this point on the planet from Earth. You can only see a place higher in the atmosphere. Look up higher, you can see the sun is also over the horizon and so the plume does not pop into the sunlight until it gets about 2,500 kilometers above the cloud deck. And this is all graphically displayed in the animation of the plume as, again, a multi-filter sequence. You can see the first two frames will show you the plume when it's visible from Earth but not yet in the sunlight. At this point it's glowing red from its own heat. It's still glowing red. Then it pops into the sunlight on the next frame and has a sort of a half-moon shape. There we go, a little half-moon shape where the top half of it is in sunlight and the bottom half is invisible because it's in darkness. The camera has rescaled itself to see the much brighter light from the scattered sunlight than the glowing red of the original plume and then it falls back and pancakes out on the atmosphere. The speed is about five kilometers, the upward velocity is five perhaps more kilometers per second and as I said it goes up 2,500 kilometers into the atmosphere. From this sort of information combined with a hydrodynamic model we can get some handle on, again, on how big the impact was and how deep it went. Back to you, Gene. Okay, that's really exciting, Andy. Let's turn now to David Levy who's going to give us an update on amateur sightings of the features being formed by impact. Yeah, finally I can say that I did get to a telescope last night, cleared up and I got to a series of them ranging from the U.S. Naval Observatory's 26-inch refractor which is not really the kind of telescope that most amateur astronomers would have in their backyards. I actually found it easier to see the impact sites, the spots, using the finder of that telescope because the atmospheric turbulence was very strong last night and here in Washington and it was difficult to actually get the image of Jupiter steady enough so that I could see the spots. But when I went to a smaller telescope, the finder of the telescope and then looking through some very small amateur telescopes placed outside the observatory I was able to see the spots very, very clearly and I wasn't the only one. I was with a seven-year-old who was also looking through the telescope. I didn't tell him where to look. He said, well, look at those spots. I have a very crude drawing that I did. Notice that the spots are at the top. This one here is the spot from G and the spot from L is over here and very clearly seen. They're by far the most obvious features on Jupiter right now. I have also reports from people seeing these spots through telescopes as small as 40 millimeters aperture. Virtually any telescope will show these through almost any observing conditions and I think since we have a lot to do I'll give it back to you. What about high-power binoculars? I tried and I couldn't do it. Oh wait, I have to retract that. 10 by 50? No, I tried but I was looking at Venus. Lucy, you're supposed to know where Jupiter is. You saw a crescent instead. I went inside puzzled. Why don't you give us an update then? Back to more electronic images which is what I can deal with better than eyeball images. Weather seems to be hampering observations around the world. Both Saratololo and Chile report clouds and snow. This is a novel way to bring you the world's weather from the astronomical observatories. And then Hurricane Amelia shut down the telescopes at the summit of Mauna Kea. Nevertheless, we do have an image from NASA's infrared telescope showing the impact of Fragment R and there are six impact sites that are visible here. And I think we're going to be calling in the armada of ground-based observers to help us keep track and monitor the spots because I certainly am getting confused and it's hard for me to keep track of which is which. Which satellite is that? That must be one of the satellites. Yes, that's right, absolutely. And on the top right is I believe it's IO based on the ultraviolet images which I bet were taken earlier when IO was further over to the left of the screen. This is an infrared image and IO is hot so therefore it shows up as a bright spot here. We have from the Keck telescope a nine-panel mosaic of images of Fragment R again. And boy, this is just food for astronomers and scientists for years. These are images starting at a wavelength at one micron and increasing up to four microns. And as I mentioned yesterday, at each wavelength we're seeing a little bit deeper into the atmosphere. And also we're seeing a time sequence here so it's a little bit more complicated seeing time and atmospheric depth variations. Let's see, I want to go through these quickly. We have an image from Loll Observatory of the same impact where the fragment, that is the R impact and the fragment plume is just seen coming over into view in the lower left limb of the planet. It's just that very subtle bump on the limb there. Right, and then IO is moved off of the disk of the planet there and it's in the upper right. McDonald Observatory, another view of Fragment R but this is more in the visible, well no, I'm sorry, in the near infrared starting at 8,290 angstroms and continuing out to 3.3 microns. And again, these are very dramatic pictures and I certainly can't do an instant analysis on these but this is food for all of us to work with over the next years. Then we have Spirex from the South Pole and this actually is an image of Fragment L showing six views in a time sequence and this complements what Andy Ingersoll showed us earlier where we can see the evolution of the plume. Although this is still evolution at a different time period because it's facing the Earth at this time but you do see initially a flash then it grows in brightness and then we can see it decay and we're going to extract a lot of information about the physics of this impact and the energies and the altitudes to which they will go down to which the impacts, the fragments have propagated. You probably should say that the very bright feature you see is actually right on the limb at that time but that's really the bright phase of the fireball of the plume. Good, thank you. Now we have a report from the Kuiper Airborne Observatory and let's turn to them as soon as they're ready. Dr. Gordon Boyaker of Goddard Space Flight Center has a report and I'll let you listen to his voice reporting it first since it's exciting. Everything worked beautifully. There's a little trouble with the telescope but the team fixed that in short order. Equipment worked beautifully and we got some very nice spectra, infrared spectra of the R spot and found some emissions that haven't to my knowledge been reported yet from this event due to acetylene and ethane. We think that this has caught these enhanced emissions are caused by heating of the stratosphere by the comet impact. The infrared spectra that we're seeing suggests to us simply that when the comet hits the atmosphere it explodes at rather high altitudes, deposits all its energy there and the major cause of the effects we're seeing is that the atmosphere is heated by maybe 100 degrees Fahrenheit hotter than its normal temperature for a period of a few hours. Okay now I want to leave up this graphic or have you look at the graphic because what we're seeing there is the emission lines are not you see a bright bar going across in most of those stacked images. The emission lines are the fainter features that are seen above it. The bright bar is Jupiter. Can we have the spectrum back please? Advance the frames please. Let me go on because I have some other things that I can report which we don't have visuals. You're probably all interested in the last impacts. U and V were reported as fizzles basically but the W impact was definitely significant. Spirex reported it to be as energetic as Fragment E but I can't remember how bright Fragment E was. We've got the spectra back. We have the spectra back from the Kuiper Airborne Observatory and I just want you to take a minute to look at... Does anyone want to care to point out where the methane emission bands are? The bottom two bars show bright spots. That must be... It's tough. I'm guessing here that they have a... One direction is along the direction of Jupiter and the other is in the spectral dimension. We assume that the vertical bands must be the lines and the emission features. Now I'm starting to see absorption lines too. Well, we're still trying to assimilate this. We're going to have to talk to the scientists and again this just illustrates the wealth of information that is present in the data that's been collected from all around the world. We can't do an instant interpretation of it, much less even a brief description. This is proving to be difficult. The other thing that I wanted to report that came in late last night was a provisional sighting of evidence of water. This was reported by Roger Kanaki, Tim Brooke, at the ball at the United Kingdom infrared telescope. They reported an emission line at 2.407 microns during the R impact. They want to stress that it is a provisional identification because as one of the Hubble scientists mentioned to me before, one line does not identify a chemical species. However, there is a line at this wavelength that is due to H2O water. It's very exciting and we will look more and look at other wavelengths and look for evidence to get a secure identification of water. There are reports of secure identifications of the molecule CO, carbon monoxide. This is the first reporting of any chemical species containing oxygen. We had preliminary reports from radio astronomers throughout the week and we have also confirmation from infrared observers at, I believe it was Marsha Reiki and it was infrared emission bands attributable to CO, carbon monoxide. The chemical reports are just beginning to come in and we're appreciating the power of spectroscopy to help us interpret the chemistry. I think I'll stop there. Okay, that's great Lucy. I'd like to add one, I tried to get Lucy to talk about this but she was, she demurred. There's a very interesting report from Ellen Howell at the University of Arizona. She reports seeing a very large dark ring surrounding an impact site but we're not sure that she's identified the right site. This ring gets to be about 90 degrees across so it goes all the way to the pole and she reports seeing the ring move in successive images over the course of about an hour. Now we're not sure whether she saw the ring move all the way from close to the impact point to that distance or not. That has to be confirmed. If she did, that would be the speed appropriate for a seismic wave but that may be premature. We really have to check with Ellen to find out how far she saw it move but we have heard that observers at Lick Observatory have also seen this large ring so if that proves to be the seismic wave that's been refracted from deep within the interior of Jupiter that would be extraordinarily exciting. It's a little bit early to say that but in any case where people have been seeing waves recorded on the surface at very large distances from the impact site that seems to be secure. Could you clarify exactly how much of Jupiter this ring is? It goes all the way from over the pole to about to the equator. It's covering half the planet. That's right, it's covering a quarter of the planet as we see it. And that means it's sampled depths where the pressure is a million atmospheres and all sorts of exotic places. If it really has done that and it's not one of your sound waves going out there that's just late in writing. I hope for those guys. Ah, me too. We should be getting confirmations of this over the next couple of days. Yeah, but it sounds very exciting. Stay tuned for tomorrow's conference. Hopefully we'll have a more complete report on that tomorrow. Don, I think we should bring it back to you at this point. Sure, and before we get started on Q&A I've told that we now have ready to roll the reports from IUE and if you want to go ahead and introduce those. Okay, we have some reports that I got excited and brought in some other things that were out of the program but we do have reports from the International Ultraviolet Explorer. The little telescope that could that's been working for 15 years in Earth orbit. Two members of the team have... We've been observing the comet collision with Jupiter using the IUE satellite as part of a very large campaign that has three separate U.S. science teams and a European science team. We've been observing 24 hours a day since the impacts began and we've been using the unique capability of the IUE satellite to observe upper atmospheric effects from the comets 24 hours a day. We began in June to take a number of spectra of the planet without any comet having hit it so that we would have an idea of what to compare with. These spectra were obtained back in late June and early July before the comet hit Jupiter. This green spectrum is the far ultraviolet light that came from Jupiter's atmosphere at a location close to the dawn limb or edge of Jupiter. This first green spectrum was taken on the dawn limb at about 40 minutes after the impact occurred and this second red spectrum here was taken on the dusk limb about three and a half to four hours later. These wiggles are indicative of changes in the composition of the atmosphere that presumably are due to the comet passing through it and releasing a tremendous amount of energy. There was a considerable amount of darkening that occurred and what we think we're seeing here is we're seeing the evolution of a dark region, the sort of dark region that people have been seeing in the ultraviolet HST images. Okay, that was Dr. Walter Harris from the University of Michigan. And we have one more. This is Dr. Hilda Ballester. I did find a mission related to the impact of this fragment but in addition we found an extended trail of emission very extending thousands of kilometers away from the planet. Originally we thought this was associated with the plume phenomena but with subsequent observations we realized that what we're imaging is in fact the train of the comet as it approaches Jupiter. This is really a very spectacular result because IUE right now is the only instrument that can in fact image the comet train and I want you to realize that although the major fragments have impacted Jupiter, there is still an extended wing of the comet approaching the planet and we plan to image it for many days to come to try to identify what are the processes producing these emissions. The observations of IUE that Dr. Ballester was reporting on were observations off the edge of the planet and she was looking along the trail of the comet. They are seeing ultraviolet emission extending above the edge of the planet along the trail of the comet. Everyone else has been looking at the comet. I think we're ready for Q&A here at Goddard. Yeah, Dr. Schumacher. Yesterday the Committee of Congress approved and authorized an activity by NASA in which they would set up radar sets to search for possible Earth-impacting comets or asteroids or bolids of some sort. How practical and appropriate do you think such an activity, which has cost the country about $50 million, is? And secondly, kind of a follow-up to that, have you learned anything from this particular comet that might assist such an enterprise? Okay, well, let me clarify what the actual language of the amendment is. NASA is being requested in the amendment to the authorization bill for NASA to report back to Congress by February 1 on a plan to carry out a search or survey and catalog of the Earth crossing objects larger than one kilometer. And I'm sure it's the intent of Congress then to then act upon that plan probably with funding in fiscal 1996. So Congress is asking NASA to come back with a plan. They have not specified what that should be. However, I'm sure that they have very much in mind recommendations of the Morrison Report, which was also a report in response to a congressional request that laid out a plan for a series of optical observatories, not radar, but optical observatories to enhance the rate of discovery over what's being accomplished now. And that report's been widely available now for almost two years. It was chaired by David Morrison. It had a group of about 50 people that contributed to that report and very carefully considered how one could effectively search the skies and carry out a survey for the objects, particularly the asteroid objects, which might hit the Earth and carry out that survey for the ones that would potentially have global consequences. So I'm confident that what NASA is going to do now is to review that recommendation and come back with a very specific plan to Congress at the time requested, which will be early next year. Wait for the mic, please. Has anything been learned from this particular impact that would increase the understanding of how to go about this catalog survey and what might possibly be done in case an Earth-impacting object is found? What we've learned from this event is that yes, Virginia, comets hit planets. And I think that had a lot to do with the amendment that's just been put forward this week. In terms of how we should do that in detail, no, our observations of the impact event have not helped, but of course our discovery of this comet in the first instance is a part of an ongoing program. That is, in fact, you might call it the precursor of such a plan as being carried out at a much more modest level. Andy, you were going to comment. Well, I'd like to make a comment and get your reaction. Jupiter is a much bigger target than the Earth, so it's more likely to get hit. It's physically bigger. It's got a bigger cross-section. Its gravitational field is bigger, so it attracts objects. And then it accelerates them so you get more bang for the same size buck, right? So we really shouldn't assume that the same kind of impacts are going to occur on Earth in our lifetime, or at least that it's likely that such things will happen on Earth in our lifetime. And I'd like to know when will the Earth get hit? When, in your opinion, will the Earth get hit by similar sized energy, by events of the same energy? Right. Well, you've missed some of our previous NASA Select broadcast where we've discussed that very issue. There is, of course, a connection between the frequency at Jupiter and the frequency at Earth. And as we've mentioned before, I think the precursor for this thing was about a 10-kilometer-sized body, and I think that we get hits like that about once every thousand years on Jupiter. So we are kind of lucky. This is not a common everyday, you know, every decade event. This is a fairly rare event on Jupiter that we're witnessing. A corresponding event on the Earth is about once in a hundred million years. So there's a huge difference in the rate at which the comparable impacts happen on the Earth and on Jupiter. However, if a comet hits the Earth, the typical collision velocity for a long-period comet, which are the ones that dominate the flux at the Earth, is about 60 kilometers per second. It's being accelerated by the Sun, of course, not by the Earth, but it's very similar, interestingly enough, to the speed on Jupiter. And also, I think the interest expressed by Congress yesterday was not for just 10-kilometer objects, but for objects as small as one kilometer, a little more than half-mile-wide objects. So we're talking about things that have a sufficiently high rate of impact about once per hundred thousand years, actually. So the odds are a little bit lower than one chance in a thousand that one of these one-kilometer guys might hit during the lifetime of people now living. But if there is one, the statistics are irrelevant. Why do we have to look for it? You're right, Lucy. You're right on. Hi. Now that all the fragments are down, I just have a couple of basic questions about what this poor battered plant looks like. Are all the impacts, are they strung out all the way around the southern hemisphere? Are they blanched in one place? And are the earlier impacts, like A, which was so unexpectedly impressive, are they dissipating into haze, or are they still have some integrity? What does it really look like? I think the comet is battered in a band. I mean, I know it is all the way around the planet. I'm sorry. The planet is battered in a band all the way around the southern hemisphere. And I'm going to let one of the Hubble Space Telescope people respond to the evolution of the impact sites. Yeah. Actually, there is some clustering. Not all the hits are equally spaced. And the picture that we see here has more than its average share of hits. But nevertheless, they are essentially at all longitudes. They're all near the 45-south degree latitude region. And I think we're going to see these, the haze particles and gases that absorb light, they're going to spread out in the stratosphere, just like in the case of the big volcanic eruption into the Earth stratosphere, over a period of time, weeks, months, and even more than a year, I expect we'll still be seeing particles as they spread further and further. And by virtue of the fact of seeing them spread, we'll learn a lot about the stratosphere of Jupiter. These particles are also absorbing sunlight and they will contribute to heating the stratospheres in addition to the heat that's being dumped there essentially immediately from the energy of the impact. So in the thermal infrared, I expect we'll see higher than average temperatures in the stratosphere for quite some time to come. And possibly the effects may even be large enough to have some effect on the stratospheric circulation. So we'll be looking for all those things. Well, while you're saying that, this is a great time not just for large telescopes, but to complement the space telescope and other instruments, amateur astronomers with good instruments and with CCDs or simple cameras should be photographing Jupiter to get the large synoptic view over time. Write down a lot of the large telescopes stop seeing Jupiter in another month or so and it starts getting really close to the sun and they simply won't be able to get to it. But smaller telescopes and amateur scopes will. It is very important for amateurs with cameras to continue photographing Jupiter as far into the sun as they can. We are already losing track of who's who in this rogues gallery and yet, in other words, we get G confused with H now and if we're going to study the long-term evolution of these things and do some Jovian meteorology, we'd like to keep track of who's who. So we need really an archive of photographs taken on an hourly basis from all over the world. Bob Cook from Newsday for Andy Angersall. Isn't it unusual to be able to see a sound wave? I can hear thunder but never see it. I can hear sonic boons and not see them. What's happening? You're right on. We were lucky to see the sound wave. Something has to condense in Jupiter's atmosphere. Some material has to form a cloud in order to see it. And from the cover of this cloud and its general appearance, it appears that we are seeing condensation of that same ugly brown material that was thrown out by the comet. And so that stuff settled out in the stratosphere of Jupiter and as the wave went by, it caused some of it to condense. And I think we're lucky. Some of the equally large impacts did not leave a visible wave. And yet, we know the wave was there. Shin Yoshikawa of NHK. From infrared image, we are seeing many impact sites remaining. And the first question is, how hot was the oil impact? And what's happening about the impact site of A? It's one week ago. How hot was the impact site A? And how long does it take to become a normal degree? Okay, I'm afraid I'm going to give you a frustrating answer. I'm not confident giving numbers from other people's images. And in fact, what the scientists are going to do next week is hole up with their data and perform careful calibrations and get some real numbers. And we have observed in a quantitative manner that it brightens and then decays for a while, but yet there are still images, there's still remnant heat at the impact sites after Jupiter rotates around and we can see repetition of the impact sites. So they do stay at some temperature, but I can't give you numbers right now. I think it's fair to say after a period of a day or so, as you look at the older sites, mostly what we're seeing is sunlight and infrared light and sun being reflected from those sites. So the intense emission from the heat dies away fairly quickly, although as Lucy said, there's still some residual warmth. I mean, those spots are warmer than normal in the atmosphere. I'll bet we can see some of these storms a year later. Jupiter, after all, Jupiter has a 300-year-old storm. I see no reason why these storms shouldn't last for a long time. This is Mark Harrow of the Houston Chronicle for Dr. McFadden. Can you tell us, from the reports you have, about how closely the grouping was for Q's, R and S and also speak to why a couple of the last ones seem to sputter, as you said? Okay. I don't have any reports of what we were expecting of seeing a nice shield image from the impacts of Q, R and S. We seem to be able to resolve them as discrete impact sites. Let's see, now I forgot your other question, which I had the answer for immediately. It was a couple of the last ones you said. Why did they fizzle? Yes, why did they sputter out? Well, our immediate hypothesis that like fragment B, which did not create a big scar or big impact, that U and V quite possibly are not as massive or the mass is distributed over a larger area and they did not make the big bang. They exploded higher in the atmosphere. I'm not exactly sure. If you look behind this, unfortunately, it's a bit behind the flag. Can somebody move that so we can see it? You can see they are very tiny. We knew that to begin with. They're right over there at the very end of the mosaic. W is off of it. And you can see that they're much fainter as seen in this image which was taken in January. These are much fainter objects who expected them to be much smaller. But W is pretty big. W is pretty big. It's off the line. It's off this picture. Right. The impact from W was as bright as fragment E. So that's like a medium-sized impact. Jim Reston for Esquire. Dr. Ingersoll, I assume what you said and what Don Huntin said and others that the consensus is growing that these things have exploded higher in the atmosphere. That solves the mystery of why water has not been seen in abundance along the way. But I wanted to go on from the details to theory now as we come near the end of our week together. There was a lot of talk about the possibility of the formation of new cyclones from this thing before it began. And I wondered as you've been watching the scene this week whether your thinking has been advanced about the formation of cyclones on Jupiter, whether they could have been caused by commentary impact. And if indeed you have grown stronger in that feeling, how big would a comet have to be or an asteroid have to be to create the big red spot? When you watch Jupiter through a Voyager images, which is really a 60-day history of the planet's weather, you see spots being born and merging with each other, which is a form of death. You see this process going on all the time. And I don't think, let's say this, it's premature to conclude that most of those spots were formed by commentary impact. There's plenty going on to form spots. On the other hand, the big question is why do these spots, which are just storms in the atmosphere, why do they last so long? And we're working on that. And one of the things we've not known about is what are the conditions deep down because we can't really apply weather forecasting models unless we know those conditions. So I think we're going to learn a lot from the longevity of these spots. And I'm hoping some of them last a long time, either way we're going to learn something about how long they last. I think in particular we're going to see the outer material drift away in the Jovian winds in a matter of weeks, but the 1,000 or 2,000 kilometer diameter central core of many of them will last. The fact that they are exploding above the water layer means that they're not getting in deep enough to really address the question of whether cyclones can be formed by comets. Is that correct? Well, we didn't design this experiment. Someone else did. And yes, I probably would have chosen to put the energy down deeper. Of course, that's still an open question, but I still think I'm completely confident we're going to learn something about the dynamics of the weather on Jupiter. I would have preferred some energy in the water clouds. We don't know how deep the red spot goes. It could just be a creature of the upper cloud deck or of the water clouds, and it could go much deeper. The energy in the red spot is just the kinetic energy of those winds going around is about comparable to the energy of a several kilometer-sized comet. However, you have to efficiently couple the energy of a comet into swirling motion, and it's unlikely that you're going to do that very efficiently. I think there's something we can add to that, and that is I also think we'll see a very long-life features, but I think they're going to owe their longevity to something entirely different than the longevity of what we've been used to seeing in Jupiter. I think they're going to be long-life because they reside in the stratosphere, which is a stably stratified layer. It takes a long time for particles to fall out of the stratosphere, and I think it's for that reason that they're going to be long-life, not for the same reasons that the great red spot has a long life, so we're going to be learning totally new things here. To my mind, that's why this is so exciting. I'll take one more question here, move to KSC, and then come back. I'm Kay Tamura from NHK, she's been broadcasting. I want to get back to the sound waves. By studying the sound waves, what can you learn about the Jupiter? What are you trying to imply by this? I really brushed over that a little fast. There are really several kinds of waves. There's sound waves propagating near the base of the stratosphere, and there are then things called gravity waves, which really involve upward and downward motion, and those waves can either propagate in the stratosphere or down in the water cloud. And the prominent wave you see matches the speed of the stratospheric, both of the stratospheric gravity wave and of the stratospheric sound wave, and we don't learn too much from that, except that because it's so prominent, it's probably the comet put most of its energy in the stratosphere. But from the speed of the slower wave, which I think is down in the water cloud, we can learn a great deal about the water cloud, and in particular, we can learn how much water there is on Jupiter just by the speed of that slow-moving, very faint wave there. And of course, how much water on Jupiter is one of the big questions, because it has to do with whether there's oxygen on Jupiter and the hydrogen-oxygen ratio of the whole solar system. There's one thing you mentioned that I think we should point out. You mentioned the greater visibility of the wave that appears to be in the stratosphere, and that's certainly true, but we have to remember that even though we see a wave in the stratosphere and apparently in the troposphere, the one down deeper is probably going to be harder to see because there are overlying clouds that make things harder to see. The mechanism, the condensation mechanism, is producing a different kind of condensation cloud, which may be more difficult to see. So the fact that we see what appears to be a stratospheric wave more prominently may reflect conditions that allow visibility rather than telling us something about the energy. So we just have to keep that in mind, I think. Although, in our defense, I and some colleagues took that into account before the comet hit in trying to decide whether we could see evidence of this deep down wave, and we concluded that if it was there, we'd see it about as well as we could see the stratospheric wave. So to some extent we've got that one covered, but of course we really don't know why we're seeing waves at all. You should hear them, but why do you see them? We'll be back here for questions later, but let's go first to headquarters, then to KSC, and we also have questions at JPL. Headquarters, please wait for the mic, state your name and affiliation. Go ahead. This is Dick Kerr, Science Magazine. Gene, you seem to your opinion that Schumacher Levy was a relatively large comet for a breakup, but its fragments were relatively large. Would you care to comment on Andy's implication that much or most of the energy of a fragment was deposited high in the atmosphere? The modeling of relatively large objects hitting Jupiter had shown penetrations of tens, if not hundreds of kilometers. Thank you, Dick, for that question. If Andy is right, and some of us are not quite ready to concede, but if he's right, I think that's very important. It doesn't mean that we're wrong about the energy. What I suspect it means is that as these comet fragments are coming in, remember, keep in mind that they're probably a pile of debris just bound gravitationally, and as they approach, that pile of debris is going to tend to be stretched out as it gets very close to Jupiter. So it may be the reason that they don't penetrate deeply is they're getting spread out such that the individual smaller pieces are getting stopped in the atmosphere rather than one chunk just burrowing on down. And that, of course, was a $64 question. We didn't know how that would be, and I think we're going to learn. And if Andy should prove to be right, I'm just as excited about that as the other model. But I think it tells us something very important about the nuclei themselves. Of course, it makes it a heck of a lot different problem to model, a difficult one. So it's going to be back to the drawing board and doing some very tough numerical modeling, now of a swarm being pulled out as it comes in, as against a single clump. But you still have the size of the swarm or the size of the single big object. You're still thinking about the same thing. Oh, sure. I think when we look at the rise of the plume, its rise time and its fall time, I think we can start to get very confident about the total energy being put in. And also, as people really start to analyze the actual thermal emission from these plumes in their early stages, that's going to give us the energy as well. Earlier I said five kilometers per second, I think 10 kilometers per second is in the right ballpark as well. There's one thing about the rise speed of the plume. There's one thing that this might relate to as we start to study the origin of this comet. Yesterday there was a very popular question that got repeated to me several times last night. Is it possible that SL9 was not a comet but an asteroid? And I really want to lay that question to rest. I think we go on the idea from the old Greek definition of a comet as being a fuzzy star or a hairy star and an asteroid as being something of star-like appearance. These are observational definitions so that we don't know how this object started. We don't know if it might have gotten its origin somewhere in the asteroid belt or if it got its origin somewhere out in the Oort cloud. But on March 25, 1993, when the object was discovered, it was a comet by our definition of what a comet is. But was it a rock pile or a snowball? That's something that we're going to find out. But it is a comet. It was a comet. That's a very important question. We'll move on to questions from Kennedy Space Center. Please state your name and affiliation, please. Yes, this is Bill Harwood with CBS News. Two questions. One for anybody about the water issue. This is ignorant on my part. How long would water be expected to be detectable if you did, in fact, throw some up there? I mean, at the level you're seeing this stuff, is that something you would have to see during the initial moments? Would it be long lived and you could detect it later? I mean, how does that work, number one? And number two, for Jean, back in May, you said that it was... you did not believe it justified the expense of trying to build something that could knock a comet or an asteroid down that was coming toward Earth. And I'm wondering if you changed your mind after watching the show this week. Let me talk about the water. The emission band that is at the position where H2O forms spectroscopic bands was first seen in emission, and that means that the temperatures were high because in order to get a gas to emit light, you need to pump in energy and make it hot. They then report that the band turned from an emission into an absorption, which tells us that the water molecule cooled. So we can... it did get heated up and cooled down. I think I'll stop there. I think there's something we can add to that. If there's a significant amount of water in the stratosphere, we ought to be seeing it. It's high enough in the stratosphere, I think, that it won't condense into solid particles at this point. And it should be distributed over a large area. And if there's a lot of water, we should be seeing it everywhere. I'll try to answer the second question. Knocking a comet down is a tough thing to do. And it may doubly tough for the case of long period comets. Short period comets, we have a chance of finding them, whether they're extinct or whether they're still active. We could find them with a survey just as we could find near-Earth asteroids. But a long period comet can only be seen by continued vigilance. We have to just keep on watching the sky. And at best, we would only get about a two-year warning. So what to do about that? I think that's a really tough problem. I, for one, am not one that's advocating that we have a standby armada of launch vehicles and nuclear weapons to go shoot them down. I don't think that's the right response to the situation. I would say the impact of long period comets for the things that are happening most frequently, they contribute about 20% of the problem. And I'd be willing to let that problem ride for a while while we try to deal with the other 80%, which are things that we can find, which are likely to be found long, long before they hit. If there's anything out there with our name on it that's going to hit in the next century, which is very unlikely, but if we found one, then we could think about real means of dealing with that and design a very specific mission to change the orbit. But as far as the comet part is concerned, I think we just should ride with that risk. After all, we're dealing with the probability of something not hitting the Earth in any time that's equivalent to the total span of human history. So we could afford to take the risk a little bit longer, and I would think in the future, our technical capabilities are going to change. They'll change dramatically, and we may be better prepared. Another question at KSC. This is Phil Chenoverth, news for Andy. Can you give us a rough estimate on what's the frequency of your acoustic waves, and if you're somehow to compress that band into the wavelength of the human hearing, what would it sound like? The frequency, now it's easier to give an estimate of the speed of the wave than the frequency. It's probably a very low frequency. In other words, you have to be able to see the crests and the troughs, the peaks and the valleys of that wave, and we can't see that. All we can see is the radius of that ring as a function of time, and so we can learn the speed, which is telling us something, as I said. But Andy, the most of the energy would be in the fundamental mode, and surely you know theoretically what that is. Oh, it's going to be a low frequency. You remember the frequency from the front of my head? Not in your head. Okay. That occurrence is like this, the current smash in Jupiter as little as 80 years as much as 1,000 years that you just mentioned. Any reason why you're leaning towards the 1,000 number and what's being used to derive these numbers? Monte Carlo analysis, looking at the moons of the Galilean satellites in the crater chains or just numerical analysis and popular guessing. Okay. I think that question was directed to me. We didn't get the first part of it. The estimate... So basically the question was, what is the basis for estimating the frequency of impact of these objects? And it comes from multiple sources. First of all, we have the discovered Jupiter family comets. We also have the discovered long period comets but it turns out at Jupiter, the Jupiter family comets utterly dominate the collision rate on the Galilean satellites and on Jupiter itself. And so we already have a fairly large sample. We've observed about 150 Jupiter family comets and for at least some of these we have estimates of the sizes of the nuclei. They're very difficult to observe but there's a handful that have been observed well enough. We know their sizes. Now we also know the size distribution by looking at the beautiful impact crater record on Ganymede, in particular the groove terrain of Ganymede which is relatively young, preserves a complete record of the craters that have hit and we can make an estimate of the age of that surface and we can then get an estimate of the flux from that. But I use Ganymede to get the size distribution. Ganymede is the moon of Jupiter. But I use the actual observations of Jupiter family comets to estimate the number that are out there. So that's where the numbers come from where we get the number of about one 10 kilometer body hitting Jupiter about every thousand years. Okay, and for Lucy, listening to IUE reports and their emphasis on how they're spending 25 hours a day looking at Jupiter, I can't help but wonder why with Hubble you're not getting the same percentage that I noticed about on the Hubble Observing Schedule still doing quasars, AGMs and so on. Is this because Jupiter's out of the field of view or that you couldn't convince the head of the institute that this was justifiable to take over all of Hubble's observation schedule? I don't know the answer to that. Could you repeat the question? Okay, the question as I understood it was why was IUE looking at comet Shoemaker-Levy-9 24 hours a day and Hubble Space Telescope was not? I think part of the answer to that is there's an intense competition of time on Hubble since it is a very new telescope and very superb in its capabilities. There's not nearly as much competition for time on IUE. I think that has a lot to do with... Well, we who have been closest to the Hubble have no complaints about Hubble or the people who've been running or the time we've got and so let's lay that one to rest. Yeah, I went to visit the operation center for Hubble yesterday here at Goddard and I think HST... I'm wearing this tie very proudly today. I think HST did just one heck of a job with this comet. It is such a blessing to have that telescope doing what it's doing, where it's doing it right now. And we're also fortunate that IUE observations are complimenting Hubble's. They're looking in different places. Hubble's concentrating on following the evolution of these objects and in IUE the scientists said, hey, wait a minute, let's look at what's behind us. So those were some smart scientists that decided to take another approach so we're going to learn more from it. The other thing to remember is that both of these are in orbit around the Earth and that Hubble will disappear behind the Earth for a certain portion of time. It's only about half the orbit that Hubble can actually look at Jupiter. And so with two different satellites with different periods and different orbits, they're really complementary. So you get more complete time coverage by being able to observe with two satellites instead of one. And I also want to add all the other observations from all the ground-based observatories. The whole complete data set is most rich in its combined form. The observatory has spectacular results but the wealth of information is going to come from the combination and combining all the results and it's unprecedented. We still have a question from Kennedy and also from JPL and we'll make it back here for some questions. Go ahead please. Okay, this is Todd Halberson of Florida today for Dr. Shoemaker or whomever might want to field it. I'm wondering if you had to sit down and make up a top three list what the most intriguing questions are that have been raised by the impacts that astronomers may go off and try to answer in the next several months. Well, as of this morning, I'd pick out one question number one and in fact it's been coming up all week. How deep did these comet fragments go? And there have been hints about this. We haven't been seeing a lot of water, which we expected to see. If the comet nuclei had penetrated deeply, we're now getting hints from the study of the gravity and acoustic waves as Andy has reported that maybe these things really did deposit most of their energy high. That's one of the real mysteries we want to get tied down. So I'd pick that as mystery number one. I would say we're still betting on the come. A lot of people are making spectroscopic observations of Jupiter now of the spots and we're wondering what new chemistry has been revealed in these spots and we're starting to get some of the answers in. So I expect some of the very exciting results now are going to come from the spectroscopy which just takes time to work on. So I'd pick that as number two. Anyone else want to throw in a number three? Are objects out there rubble piles? Are they snowballs? Are they single rocks? What are they? Well, that's part of question number one. I think we'll get the answer to that if we really know the penetration. And is there water on Jupiter? Right. And just one more from Kennedy here. And I'm not sure who to address this to, but I'm wondering how soon images from Galileo will become available and how they'll compare to what we've already seen from HST and ground-based telescopes. I think it'll be a matter of days. No. It's going to be months. Mid-August. The Galileo images will be trickling down in a matter of months. They will not compare with any of the images you've seen what Galileo is going to contribute and it's very important, really, is the time history of the flash as the object goes in. And we're going to have, because Galileo is around, you can see the flashes. It's the only object that has good cameras that can see the flashes. We're going to get that time history, which no one else can get. Andy, we've already got the first one. That's from the photopolyrimeter, and we're getting the data down now. We've got two already. Well, I was thinking of images. And the images will be coming down in a matter of months. Yeah, but the time histories are going to come from that photopolyrimeter. That's true. And we're getting them. We're getting them right now. Yeah, I know on the internet the Galileo team is still trying to get the best impact times so that they can choose the images they really want to bring down as soon as possible. You know, I'm kind of glad that we're going to get a little bit of an information after this wealth of data we have before part two comes with the Galileo images because that's going to be a whole other thing and really very exciting again when they start coming down. We'll move on to JPL, Jet Propulsion Laboratory in Pasadena. Please state your name and affiliation. David Garcia with Fox Television News, Los Angeles. Dr. Ingersoll asked my question. Is there water on Jupiter? And I don't want to jump the gun, but I mean the fact that even a provisional sighting as Dr. McFadden was saying is there. I mean, can you say anything at all about the essential elements of life from this water? What was the last six words? Say anything at all about what? The essential elements of life on Jupiter. Why? Life on Jupiter? Central elements of life on Jupiter. Yes, oxygen, carbon, nitrogen, and oxygen, and hydrogen. Well, the idea that Jupiter formed out of the same material that the Sun formed is so central to our understanding of the formation of the solar system that none of us can conceive of a Jupiter without oxygen. And that's why we're advancing these alternate hypotheses, the comet didn't go deep, et cetera, et cetera. But of course, science, every theory can be shaken, and the Galileo probe will enter the Jupiter atmosphere in December of 1995 and is going to penetrate the water cloud if it's there, and it may answer that question. But certainly we were absolutely right to take advantage of this probe when it happened. Another question from JPL? Okay. All right, let's come back here. Any further questions? Matt Crenson, The Dallas Morning News. I've heard a lot of questions this week about where some of these elements and compounds that have been discovered are coming from. Is that really an important question because if it comes from the comet, can't you assume that in the past, comets have brought it to Jupiter? For example, water? Well, a planet like Jupiter is thought to form in a fundamentally different way than a planet like the Earth. Jupiter pretty much collected together more or less everything that was out there, all the hydrogen or most of the hydrogen, helium, all the light elements, as well as the heavy stuff. Whereas the Earth really collected the heavy stuff, the rocks and the iron, and may have acquired its lighter elements, the stuff of our oceans and atmosphere, at a later time, and that veneer of volatile elements may have come from comets and so on. But Jupiter being as massive as it is, probably formed and really sampled the solar nebula much better than the Earth did, and therefore it probably drew everything in with it, including the oxygen. And that's why I said we have a great deal of trouble imagining a Jupiter without oxygen. It would have to send us back to the drawing board on solar system formation. Another question. When you think about condensation sequence, even the material out there in the nebula at the position where Jupiter formed, likely the oxygen was condensed out in the form of ice and then in the form of silicates, and they were then accumulated by Jupiter and formed a core, and then the gas came down, but there were probably lots left over. So there may have been many, many things like comets, perhaps a hundred Earth masses of this stuff, that then was swept up at a late stage before the space between the planets was cleared up. Let me ask you, can you imagine a Jupiter without oxygen? I just told you how it got there. So I think the question, did they come in the form of comets? It's not an irrelevant question. I think it's a very important question in how it actually got delivered. And in fact, all the giant planets may have a cometary component of ice and things. We have time for a few more questions here. Okay. Deborah Zebrenko Reuters. This is a real quickie, but it's sort of an emotional one for you all. Before the first impact was seen, I think it was Mrs. Shoemaker who said she almost felt like shedding a tear for this poor dying comet. Before you guys start arguing about what you have learned from this, do any of you feel, you know, post-impact let down? Are you all depressed that it's all over? Post-partum depression. It's sad to lose the comet, but it did such a beautiful job we can hardly be sad. You know, it's been such an extraordinary experience we're learning so much that I would far rather have had the comet hit Jupiter than not to. I used to have a post-voyager let down which would occur during the months after a voyager encounter. Voyager encounters were similar, just a flood of new information, and I'm sure I'll miss these good old days in a few months. Miles O'Brien with CNN. Jupiter will disappear from Hubble view at the end of August or so I'm told up in Baltimore and will not be back in view until January. How much will this hinder your ability to track the dissipation of these clouds? How much of a gap will that provide? We'll have time to analyze our data and think about what we learned from this summer. I mean, it's a relief to me, but we will lose some information nevertheless. Yeah, that's why it's so important for the ground-based telescopes, which can follow Jupiter a little bit more as it gets closer to the Sun, and the amateur telescopes that can follow it right into the twilight to keep on going. And then when Jupiter reappears later on in the fall in the morning sky, then as it gets higher and higher, the bigger and better telescopes will be able to pick it up again. But remember, Spyrex at the South Pole can keep watching Jupiter until sunrise is down there. That'll be about September 21st, and even as the Sun comes up, I'm not sure just what the conditions are at that telescope. They may be able to follow Jupiter even a little bit after sunrise. We could take one more question, and we need to wrap it up, Kathy. This is not a very poignant wrap-up question, but Kathy Sawyer from the Washington Post, I'm not clear on what's left of fragment A that started all this excitement, and Hoopla, are we seeing merely the heat residue or is there still some brown comet stuff hovering there still in a package? There's definitely still brown comet stuff there, and I think there will be for a very long time, and I agree with Andy. I expect to see me seeing things a year from now. I expect things will be quite mixed up though and diffuse. I don't think we'll be able to identify individual spots a year from now, but we definitely see A is still there. At the same time, we see things are changing, and I don't remember exactly what A looks like, but I remember that D and G were very well-separated spots initially, and now they seem to have coalesced into something that's very peculiar looking, and I think tomorrow Heidi Hamill may have a story together on the short-term evolution of some of these things that we've been looking at, so come back tomorrow. I think that makes a pretty nice segue. Yes, tomorrow at 11 o'clock Eastern Time, 11 a.m., that is, and Heidi Hamill will be here as will Melissa McGrath and our other panelists will be here, and we will have the latest information at that time and some information about the changes that we're already seeing on Jupiter over this last week. I've got a couple of program notes before we move on for teachers who may be watching, and mid-September NASA Teacher Resource Centers will have a comment slide set for you to use in the classroom to find the nearest center near you Contact NASA Core at 216-774-1051, extension 293 or 294, and we'll have a graphic with that coming up after the show. Well, here it is now, and we will replay all the images and graphics and video from the program after the program today, and for those who would like to see it again or miss it the first time, we will replay this press briefing in its entirety at 8 p.m. Eastern Time this evening, and I think that was all the notes I had to pass on. Thank you very much for coming, and we'll see you again tomorrow at 11. We've been observing the comet collision with Jupiter using the IUE satellite as part of a very large campaign that has three separate U.S. science teams and a European science team. We've been observing 24 hours a day since the impacts began, and we've been using the unique capability of the IUE satellite to observe upper atmospheric effects from the comets 24 hours a day. We began in June to take a number of spectra of the planet without any comet having hit it so that we would have an idea of what to compare with. These spectra were obtained back in late June and early July before the comet hit Jupiter. The green spectrum is the far ultraviolet light that came from Jupiter's atmosphere at a location close to the dawn limb or edge of Jupiter. This first green spectrum was taken on the dawn limb at about 40 minutes after the impact occurred, and this second red spectrum here was taken on the dusk limb about three and a half to four hours later. Wiggles are indicative of changes in the composition of the atmosphere that presumably are due to the comet passing through it and releasing a tremendous amount of energy. There was a considerable amount of darkening that occurred, and what we think we're seeing here is we're seeing the evolution of a dark region, the sort of dark region that people have been seeing in the ultraviolet HST images. Equipment worked beautifully. There was a little trouble with the telescope, but the team fixed that in short order. Equipment worked beautifully, and we got some very nice spectra, infrared spectra of the R spot and found some emissions that haven't, to my knowledge, been reported yet from this event due to acetylene and ethane. We think that these enhanced emissions are caused by the heating of the stratosphere by the comet impact. The infrared spectra that we're seeing suggests to us simply that when the comet hits the atmosphere, it explodes at rather high altitudes, deposits all its energy there, and the major cause of the effects we're seeing is that the atmosphere is heated by maybe 100 degrees Fahrenheit hotter than its normal temperature for a period of a few hours. We did find emission related to the impact of this fragment, but in addition, we found an extended trail of emission extending thousands of kilometers away from the planet. Originally, we thought this was associated with the plume phenomena, but with subsequent observations, we realized that what we're imaging is in fact the train of the comet as it approaches Jupiter. This is really a very spectacular result because IUE right now is the only instrument that can in fact image the comet train, and I want you to realize that although all the major fragments have impacted Jupiter, there is still an extended wing of the comet approaching the planet, and we plan to image it for many days to come to try to identify what are the processes producing these emissions. For more information about the NASA STI program, please write to the NASA Center for Aerospace Information or call us at 301-621-0390.