Planetary Radio: Space Exploration, Astronomy and Science - Return to Mars: Two Rover Landing Sites Chosen

Episode Date: April 21, 2003

Matt Golombek tells us about the Mars Exploration Rover landing site selection process and the exciting destinations just chosen. What objects hold the solar system's speed record? We'll find out from Emily.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

This is Planetary Radio. We're headed back to Mars, and we know where we're going. Hi everyone, I'm Matt Kaplan. Dr. Matt Golombek of JPL will be here to tell us where two big ro. Hi everyone, I'm Matt Kaplan. Dr. Matt Golembeck of JPL will be here to tell us where two big rovers will land and a little about the just completed site selection process. Too bad those rovers won't get there as fast as sun grazers. Emily will tell us about these comets that hold the solar system's speed record. And Bruce Betts has traded his shirt and tie for a loud Aloha shirt and a trivia question

about a famous Mars mission of several years ago. We're glad you've selected our site. I'll be back with Matt Golombek right after this. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, What are the fastest moving objects in the solar system? Comets are the solar system's fastest solid bodies. The speed of a comet depends on the size of its orbit and its proximity to the sun. An object in space will reach its fastest

orbital speed when it passes closest to the Sun at a position in its orbit called perihelion. Among short-period comets and asteroids, an asteroid called 1995 CR and a comet named Machholz 1 are the fastest. At perihelion, both of these objects are eight times closer to the Sun than the Earth is, and reach speeds above 110 kilometers per second. You can see animations of both objects on our website at planetary.org. For comparison, the better-known comets Halley and Hale-Bopp reach more leisurely maximum speeds of only around 50 kilometers per second. But these short-period comets and asteroids are left in the dust by another class

of solar system speed demons, the sungrazers. To hear about sungrazers, stay tuned to Planetary Radio. Anyone who followed the gloriously successful Mars Pathfinder Sojourner mission a few years ago should remember Dr. Matt Golombek. He was project scientist, which meant, among other things, that he was frequently in front of TV cameras telling us about how well things were going.

His involvement with Mars sure didn't end with that mission. Dr. Golombek now joins us from his office at the Jet Propulsion Lab to talk about another milestone, upcoming milestone in our exploration of the red planet. Dr. Golombek, welcome to Planetary Radio. I'm happy to be here. You were co-chair of a very important process that just a few days ago decided on a couple of spots that we will get a much closer look at on Mars. Absolutely. Our NASA headquarters just announced the selection of the two landing sites

for the two Mars exploration rovers, and that's a very important milestone because it's been a two-and-a-half-year effort of research and analysis involving literally hundreds of people. Now, I take it, and we're going to talk about those sites, of course, but I take it that there were elements in this process of site selection that were different than how this may have been handled in the past. Oh, every single landing site selection becomes a unique event if for no other reason that the spacecraft that you land are slightly different. And then the characteristics of how the spacecraft lands is all important in site selection. But also the level of information

and knowledge is wildly different for each of these. These are very special missions. I mean, we already mentioned Pathfinder and Sojourner, that little rover that could. But we're now talking about these twin spacecraft, still known as, I think, MER-A and MER-B, although they're going to get more interesting names someday soon. Right. But these are quite advanced over Sojourner, right?

Oh, yeah. Sojourner was the first little baby step, and basically we, now speaking Pathfinder, we, Pathfinder, developed a robust landing system, and really MER is improving on the rover that's inside. We had this little rover about the size of your microwave oven, and the MERS spacecraft have a rover that's the size of your desk, with much more advanced instruments, much more capability in terms of the science that they can do, and much farther that they

can go and really explore the surroundings. Yeah, I was fascinated to see that they weigh well over ten times what Sojourner did. Yeah, that's right. And Pathfinder, the real difference was Pathfinder had a lander that was stationary and then a rover that pretty much went around the lander. And in this case, the rover simply drives off the tetrahedral lander, and the lander is dead on arrival. And basically the rover carries everything it needs to communicate

directly with the Earth and through satellites going around Mars. So the range is, you know, 10 times further. And the capabilities, the number of instruments, and what it can do on the surface is just light years ahead. Now, I should mention that there is an excellent article about not only these twin rovers, but about the sites that have been selected on the main web page of the Planetary Society, planetary.org, which may be where our audience is listening to this if they're not tuned in to KUCI. We should talk a little bit about those sites since that's this process that you have been co-chairing. These are sites that I am told uh stephen squires who is sort of the principal scientist this time around is very excited about very pleased by the selections yeah in this case

what we did for the process was really uh in a sense the same way we handled the pathfinder site selection process is you open it up and you let pretty much everyone in the science community have a say about where they think the mission should go and what important science that they can do. And it's really that outreach effort that's so important because, you know, not any one person knows everything and you want to get the full benefit from the entire community to identify potential sites. So really, this time around, the MER landing site selection is the first time that science really drove the down selection of the specific sites. In all previous site selection efforts, engineering has been the dominant number one concern.

That's still arguably the case for MER. You know, you have to land safe or you don't get any science. But on the other hand, we had enough sites to start with that we could really look at the places where there was compelling, I say compelling evidence for liquid water in the past. And that's really the goal of both this mission and the Mars program in general, to look at the ancient environment, try to understand if it was warmer and wetter, and if it was possible that it could have been habitable.

Could things have actually lived in that environment? And these spacecraft, these rovers, are very much designed to look for that evidence. That's right. These are, you know, I always said that the Mars Pathfinder rover was a one-foot geologist, and in this case, these are even better geologists, and they're bigger ones, too. I guess they're three feet high. But these are really much better suited to identifying the mineralogy, which is how the elements are arranged into stable minerals.

And that's really the currency that geologists use. Minerals, if you can identify the minerals that form the rock, you can identify the rock type first. And from that, you can uniquely identify the environment in which that rock forms. That's really a powerful tool that geologists have. You can understand the rocks. You can understand the rocks, you can understand the environment, you're really deciphering the ancient history of the planet by looking at the rocks. And it's really, really key to go to the place where you have the best chance of uncovering that evidence. So imagine landing with this spacecraft, and you look around with a regular color imager,

but also this thermal emission spectrometer, and you look for really the interesting rocks. And then you go up to those rocks, and you have a series of instruments on an arm that can be placed up against those rocks. And the instruments include an alpha particle x-ray spectrometer that gets at chemistry of the rock, the Mossbauer spectrometer that gets at the mineralogy of the rock, a microscopic imager for looking at the fabrics and textures and colors of the rock, and then an instrument called a rock abrasion tool, or RAT, that can eat away the outer weathering rind of the rock, really scrapes it off and actually drills into it in a sense to get at the fresh, unaltered rock underneath it.

And that will really help in the dusty environment of Mars, where dust can kind of coat things and shield the real identity of the rocks. Yeah, I have to admit that I was very excited when I read about this tool that's going to file away some of that outer surface. Yeah, and that was clearly the frustration on pathfinders. We didn't have that kind of tool, and basically all the rocks looked like they were coated with some amount of very fine-grained dust. And we really had to infer what the native rock composition was

by trying to back out that dust from the measurement. And that's a hard thing to do. But much, much better to be able to actually get rid of that weathering rind and look directly at the unaltered material. Well, these rovers start to sound like Swiss army knives with brains. After we come back from a break, we can talk a bit about these two very interesting sites. I'd be happy to. Our guest is Dr. Matt Golombek of the Jet Propulsion Laboratory near Pasadena, California. We're going to pick up this conversation about the just-selected landing sites for the Mir rovers right after this.

This is Buzz Aldrin. When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system. That's why I'm a member of the Planetary Society, the world's largest space interest group. The Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets. We sponsor the search for life on other worlds and we're building the first ever solar sail.

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at our exciting and informative website, PlanetarySociety.org. The Planetary Society, exploring new worlds. Matt Kaplan back with Planetary Radio, and our special guest this week, Dr. Matt Golombek of the Jet Propulsion Laboratory, who has just helped to make this decision as to the two landing sites, one for each of the rovers that will be headed to Mars with any luck in about a month. So let's actually jump in and talk about these sites that have been chosen. The first of them, if I can pronounce it correctly, Meridiani Planum, but also dubbed the hematite region. Yeah, this is a remarkable location. The thermal emission spectrometer aboard

Mars Global Surveyor took global mineral maps of Mars and there was one location that stood out like a Thor's thumb, this light bulb going on and off showing this concentration of a coarse-grained gray specular mineral called hematite and all of our models for how this particular mineral forms, remember this is the currency geologists use, suggests that the dominant formation mechanism involves formation in liquid water or in a hydrothermal deposit. So here's this unique data set that's blinking on and off that says, you know, in a sense, water here.

And as we started investigating and looking at it, it became just practically the perfect landing site. It's absolutely the smoothest, flattest, safest place we've ever investigated in any detail on Mars. And what's so astounding about this is the amount of information we've brought to bear in terms of understanding the surface characteristics and the hazards. And literally, the locations that were selected are the best studied, best imaged, best understood locations in the history of Mars exploration. I mean, when you look back at the previous landing site selection efforts, we knew just very little, so primitive compared to the wealth

of information that we've been able to direct at these locations by both the Mars Global Surveyor spacecraft, the orbiting spacecraft, and now the Mars Odyssey. And those results have really helped us understand these locations in detail. So as we learn more, we're able to learn more. That's right. In a sense, you pick a site that looks like it's safe and scientifically interesting, and then you direct the Mars Global Surveyor and the Mars Odyssey spacecraft to actually image those locations. And then as you gain knowledge from that location, you become much better informed about what the surface is like

and, in fact, how safe it is and whether the spacecraft has a high chance of succeeding there. Sure. What about this other site, the Gusev Crater, which is just a little bit farther from the Martian equator than the hematite region? Yeah, the hematite is pretty much near the prime meridian and pretty darn close to the equator. And Gusev is all the way around the other side of the planet, and that's actually good for operations. And it is unlike the hematite site or the meridiani site, which has this mineralogical indication of water. The Gusev site is what we call a geomorphological or morphology indicator of water because it's an ancient crater about 160 kilometers in diameter that has this smooth flat floor with an 800

kilometer long channel that has emptied into the crater and actually taken out a chunk of the rim. And it looks like this channel was formed by running water. And this water drained a big section of the Martian highlands and entered into this crater. So it's basically interpreted as a crater lake, a place where water drained from the highlands and brought those highland rocks and deposited them in a lacustrine, a lake environment. A perfect, perfect setting to look at what kind of environment it was. I mean, literally, the sedimentary rocks would tell you whether liquid water was stable. Now, is this crater at all a more challenging landing site than the Meridiani Planum? Yeah, this one, as I said, Meridiani Planum, with all the data we've

uncovered, is really the smoothest, flattest, safest location we've ever investigated in detail. And Gusev is a little bit more challenging. And so the final selection, which is a very, very interesting weighing of both the safety and the science. Clearly you don't want to just go to a place that's just safe but doesn't address the main science objectives of both the mission and the program which is this this water this environment. You know what's the point? You don't want all this trouble to go to Mars you want to go to a key place where you can really uncover spectacular new information. And that's really the test here, is that the selection of Gusev is an acknowledgement by

everyone in the Mars program and NASA headquarters that they're willing to take a little bit more risk, not a lot of risk, but a little bit more risk to get at this all-important question. And that's really the spirit of exploration. You don't want to just go to a safe place that's boring. You want to go to a place where you can really learn as much as you possibly can. I have to think that with the hundreds of people that you mentioned in the international scientific community who participated in these selections, there must have been a few people who were a little disappointed

that their choices maybe didn't quite make it into the winning two. Oh, I'd say they're pretty darn small. The dominant overwhelm, we actually had votes during the open landing site workshop, and these two sites were the overwhelming scientific favorites, just about unanimous, not quite. There was always one or two people that have their own little pet location. But as the process continued and as other sites were, in fact, taken off the list because of concerns over safety, that really looked like the spacecraft would not be safe going to those locations, looked like the spacecraft would not be safe going to those locations.

These were just far and away the clearly most compelling locations you could go. And all the way through the workshops, there was just overwhelming support for these locations. So I really think the science community is cheering over the selection of these two sites. So now we wait for these two spacecraft to start their journey to Mars. And unfortunately, we learned just a couple of days ago that beginning that launch is going to be a little bit delayed. Yeah, that's right. The first one, MER-A, has been put off a week to fix a central electronics board to guard it from having an improper electrical impulse that happens

when the cable cutters slice the connections between the lander and the back shell and so on. And it's actually very fortunate that this was discovered early on so it could be repaired and give us a much better chance. And Murby, we have even more time to repair that. Yeah, MER-B is still open. So actually, there's a MER-1 and 2 and a MER-A and B. I won't go through all that.

But the other one is open. It's pretty easy to correct that. So now we're on for, I think, the tentative schedule for the first launch is June 6th. And we're hoping to maintain the launch of the second one at June 25th. And the arrival times are fixed. We would target MER-A, the first one to launch to, Gusev Crater, and it would arrive, again, that's a fixed time, on January 4th, 2004. That's a fixed time on January 4, 2004.

And then exactly three weeks later, on January 25, MER-B would arrive at Meridiani. And the selection of A to Gusev and B to Meridiani is dictated by the latitude those sites are at and where you get the maximum energy and lifetime and data return, scientific data return. And, of course, all of us at the Planetary Society are very excited about both of these, and especially Marais, because we hope that that January 4th landing date holds up. It'll be happening during our next PlanetFest in Pasadena and also on the web. And, of course, we'll be looking for participation from, I hope, you and lots of other folks at JPL in that event. Yeah, I still remember the Planet Fest during Pathfinder.

Right. And I went down there at some point during it, and this room of 1,000 people stood up and cheered. I was going to say you got a standing ovation. And I don't think that doesn't happen often to old scientists. Not often enough, anyway. But, no, that'll be great. And, again, those arrival dates are fixed, so you can schedule them in. I'm very interested in both of them.

My own personal area of research is really trying to infer the surface characteristics at the lander scale from the remote sensing data set. Because if you think about it, these landing sites are ground truth points for your remote sensing. And the better you can understand how these two data sets compare, the better you really understand what Mars is

and what the variability and what kind of materials are there. And so I'm very interested in testing how these sites look compared to what we've predicted. The Meridiani site really looks very different from a remote sensing point of view than any of the three locations we've been to. And I would predict it will look entirely different from the three places we've already been to, and that will be very, very exciting. Dr. Golombek, we're about out of time. You've been at this for a lot of years.

You have not lost any of your enthusiasm. Well, how could you lose enthusiasm when you do something you love? Dr. Matt Golombek has been our guest. He is speaking to us or has spoken to us from his office at the Jet Propulsion Laboratory. No doubt we will be hearing from him again as the MER A and B missions get underway and hopefully arrive safely at two absolutely exciting, fascinating spots on the Red Planet. Dr. Golombek, thanks again for joining us. My pleasure.

I'm Emily Lakdawalla, back with Q&A. What are the fastest moving objects in the solar system? Sungrazers. Sungrazers are comets on highly elongated orbits that pass very close to the sun. A sungrazing comet discovered by the Soho spacecraft in 1996 achieved a maximum speed of over 1,000 kilometers per second, over 30 times faster than the Earth moves in its orbit. At this speed, you could make the trip from Los Angeles to New York

in just over three seconds. The highest theoretical speed for a solar system object would be even faster, about 1,600 kilometers per second, for a sun-grazing comet in a nearly parabolic orbit with its perihelion near the edge of the sun. However, these super-swift sun-grazers pay dearly for their reckless lifestyle. Eventually, in a final sunward plunge, nearly all of them are consumed by the solar inferno. Got a question about the universe? Send it to us at planetaryradio at planetary.org. Be sure to provide your name and how to pronounce it, and tell us where you're from. And now, here's Matt with more Planetary Radio.

Bruce Betts, aloha! Aloha! Aloha from Kauai. And he's really there this time, folks. We're not kidding around. He finally got to take a vacation. Bruce Betts, the Director of Projects for the Planetary Society, joining us so

dedicated, even from his vacation in Hawaii, for What's Up? Formally, this is not vacation. It's solar radiation research and also research into wave action and fluid mechanics. Yeah, I definitely recommend the 30 SPF for your controlled experiment.

Thank you very much. All right, what can people see in the sky? We've got, once again, but going fast, five naked-eye planets, naked-eye. Mercury is low in the west-northwest just after sunset, and both fading and will be getting lower and lower each night. Saturn up nice and high in the early evening above Orion. Jupiter extremely bright directly overhead any time in the evening. You've got Venus still very bright in the morning in the east shortly before sunrise.

And Mars 60 degrees to the right of Venus now and getting brighter gradually. And if you have trouble finding Mars, look on April 23rd in the south-southeast, and it will be right next to the last quarter moon. We also have a meteor shower coming up, although it does fall into the sort of, to use a technical term, lame-o meteor shower category. But if you're in a nice dark site, still something fun to look at, the Lyrids, and that peaks on the evening of April 22nd, 23rd, and the average number of meteors per hour for the Lyrids is about 15 per hour.

So on average, you'll see one every four minutes. That's not very many. I mean, this is almost an anti-meteor shower. So you go out on this night and you see fewer. It actually absorbs meteors that normally fall. It's very strange. Scientists are still, no. But yes, it is one of the smaller ones, but as opposed to the random meteor flux,

they would all appear to radiate from the constellation Lyra. If you've always wanted to see a single A-league meteor shower, here would be your chance, folks. Well, it's a much friendlier environment, and the meteors are cheaper. That's true. Okay, now you got me. All right, this week in space history, April 25, 1990, the Hubble Space Telescope was deployed. Yay! Couldn't see very well at first, but once we got it, a contact lens, it was fine. Exactly. And on to random space facts! You're going to do the echo yourself now? Well, I wasn't satisfied

with the quality of the last couple. No, I'm kidding. Anyway, the gravitational force at the surface of Mars is only about one-third as strong as the gravitational force at the surface of the Earth, actually 38%. So the way it's usually phrased in fun land is you would weigh 38% less on Mars than you do on Earth, one of the reasons that Mars is such a great planet. Let's move on to the trivia question. Trivia question. Last to the trivia question. Trivia question. Last week's trivia question was, what's the largest moon in the solar system? What did we get there, Matt? A ton of correct answers.

We only had one that was not correct. And what was the correct answer, Bruce? The correct answer being Ganymede, which is actually larger than two of the planets, Mercury and Pluto. We had some terrific ones. We even had one where a guy mentioned by how much Ganymede outgrew the nearest contender, which is, is it Titan? Yes, I believe so. Titan. 2.7%. Saturn, Ganymede, the mood of Jupiter.

And our winner hails from Brownstown, Michigan this week. Her name is Kim, Kim Wenzel. And Kim, you will be receiving that wonderful Carl Sagan Memorial Station T-shirt this week. Thanks very much for entering. For this week, we've got a question that I dug out because of our guest, Matt Golombek, who is the project scientist for a Mars Pathfinder mission. So I looked for a little bit of an offbeat Mars Pathfinder question. How many radioisotope heating units did the Mars Pathfinder mission use to keep its electronics warm and toasty?

Not really warm and toasty, but keep them from freezing during the cold Martian night. I am fascinated by this one. A lot of stuff comes to mind, but I don't want to give out any hints to people. But I can't wait until next week when we get to talk about the answer to this one. I, too, am giddy with anticipation. Go to planetary.org and follow the links to Planetary Radio to find out how to enter our trivia contest. The winner will once again receive a Carl Sagan Memorial Station t-shirt, and mahalo.

Mahalo to you, and don't forget, everybody, that you need to get those entries in by Thursday at noon, because Bruce and I actually record this shortly after that. And I guess you'll be back in town next week. I don't even know how long you're over there. I can't actually discuss that with you. It depends on how long the research takes, but yes, on the order of a week. All right. Well, keep the solar cane handy, too, and be sure to look up at the sky now and then.

I bet you're going to do that anyway, aren't you, Bruce? I am indeed. And remember, everyone, when you look up at the night sky, think about hanging loose and shakabra. Mahalo and good night. Aloha. Aloha. And mahalo to all of you for tuning in this week.

We'll be back with a new show next Monday. In the meantime, would you consider making a pledge of support to KUCI, especially if you're listening to us right now at 88.9 FM or at KUCI.org. It's the best way to make sure you'll keep hearing an alternative approach to radio that can't be found anywhere else. Thanks very much for your support. Have a great week.