Planetary Radio: Space Exploration, Astronomy and Science - Opportunity Reaches Endurance Crater on Mars

Episode Date: May 10, 2004

Steve Squyres and Phil Christensen discuss Opportunity's latest goal, Endeavour Crater; Emily Lakdawalla knows how to find a spacecraft sailing out beyond Pluto, and Bruce Betts has a lock on a couple of comets.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Opportunity and Endurance, this week on Planetary Radio. Hi everyone and welcome back. I'm Matt Kaplan. The big news came from the Red Planet last week. The Mars Exploration Rover team announced that Opportunity had reached Endurance Crater. You'll hear part of the Jet Propulsion Lab press conference, followed by exclusive comments from planetary scientist Phil Christensen. He's responsible for the vital mini-test instruments on both rovers. Bruce Betts is watching comets and giving away another T-shirt on What's Up.

And we'll get underway right now as Emily answers another of your great questions. I'll be right back. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, A story about Voyager 1 made me wonder, how is the exact position of a spacecraft in space calculated? The positions of functioning spacecraft can be calculated by spacecraft navigators using information from the deep space network of radio antennas.

To find the Voyagers, the tracking antennas have to be precisely pointed toward a signal broadcast by the spacecraft. The tracking antennas, measuring 30 to 70 meters across, are moved back and forth across the expected direction to Voyager until the strength of the radio signal from the spacecraft is at a maximum. This process defines the direction in the sky where the spacecraft is, or at least where it was when the signal left the spacecraft. The direction is half the problem. The other half is distance. Figuring out the distance to the spacecraft involves something called ranging. A series of very short radio signals is transmitted from the ground,

received by the spacecraft, and transmitted back to Earth. The time it takes for the signal to make this two-way trip is called the delay time and can be measured by spaceship navigators to an accuracy of billionths of a second. Multiplying the delay time by the speed of light and dividing by two gives you the distance to the spacecraft. This may sound relatively simple, but there are a lot of other factors that can make it tough to predict the exact location of the spacecraft. To find out more, stay tuned to Planetary Radio.

exact location of the spacecraft. To find out more, stay tuned to Planetary Radio. Mars Exploration Rover Opportunity's six-week sojourn across the Meridiani Planum has brought it to what may prove to be the most exciting place we've ever been on Mars. Endurance Crater is much bigger than Eagle Crater, where the probe touched down. The 430-foot-wide bowl is up to 66 feet deep, depending on where you stand around its edge. And it's chock full of wonderful, and at least so far, mysterious geology. Principal investigator Steve Squires and some of his colleagues sat down for a press briefing on Thursday, August 6, and they brought along some spectacular images. You can see the pictures and read an in-depth article about what Steve and others had to say at the Planetary Society's website, planetary.org. This being radio,

we thought you might like to listen in. Later on today's show, we'll be joined by planetary scientist Phil Christensen of Arizona State University for some analysis. First, though, here's Endurance tour guide Steve Squires, who is obviously pretty thrilled by a panoramic view of Opportunity's new home. The crater is more than 100 meters in diameter. It's over 10 meters deep. How deep it is sort of depends on where you measure it from. meters deep, how deep it is sort of depends on where you measure it from. The best thing of all, from a science perspective, is when you go up close to the rim of this crater,

we see enormous outcrops, much bigger than anything that we've seen before, of layered rock. These rocks, we believe, lie lower than the rocks that we saw at Eagle Crater. They preserve a record of what came before the events that took place at Eagle Crater. If you look along the very top of these cliffs, and they are cliffs, you'll see busted up rock, rubble. This is the ejecta that was thrown out of the impact, and it's busted up, it's comminuted, it's broken. But below it is intact rock, and that intact rock is the stuff that contains the record that we hope to be able to read. If you look within the crater, you see a lot of old familiar things, too. The hematite-bearing spherules, the blueberries as we call them,

are all over the ground along the upper reaches of the crater. But when you get deeper down in the crater, what we're seeing is mostly sand, sand with a composition like that of basalt, which is what lies underneath the blueberries, the hematite that we've been driving across. Some of the rocks on the wall of the crater are sort of tilted and flat. They sort of look like paving stones. There's a lot for us to figure out here, but the most appealing, the most attractive, the most scientifically important part of all is what you're seeing right here. And it's this lovely exposure of bedrock that is going to tell us much about what happened in Meridiani Planum before the rocks that were deposited at Eagle Crater were laid down. Now, I want to give you a sense of scale and what we're dealing with here, because this is fundamentally different from anything that we have seen before.

And again, I want to take you back to Eagle Crater. Okay, remember when we landed. We landed, we looked out, we looked across a crater, and we saw a wall of bedrock. And we thought, this is great, big outcrop of bedrock. And when we first saw it, we nicknamed it the Great Wall because it looked like this massive wall of bedrock. But then we began to realize the true scale of what we were dealing with. realized the true scale of what we were dealing with. And the next image, which is also from long ago, shows the real scale of our rover and this tiny little one foot high outcrop that we had at Eagle Crater. Now that one foot of rock had a marvelous story to tell us, but it was a tiny

amount of rock. This is a big hole in the ground. Okay. Now what that means, it's good news and bad news. It's good news in the sense that it exposes a lot of rock. This is meters of rock, and that means lots of history. But it's bad news in the sense that this is a dangerous place. This is a dangerous place. At Eagle Crater, we could rove with impunity over whatever there was. I mean, we could drive over anything in our path. Here, there are cliffs that the rover could fall off and die if we're not careful. So we are going to proceed cautiously. We are going to proceed slowly. We're going to proceed very, very methodically

here. We're going to start by doing a traverse all the way around the crater, 360 degrees probably. And we're going to shoot it from different angles with pan cam, with mini tests. We're going to do everything we can with all of our remote sensing instruments, the ones that look off into the distance, to characterize this crater in detail. And then what we hope to do, we hope to do, is find places along the rim of the crater where we may actually have safe access. We're not going to be plunging over any cliffs here. We want to find safe access, traversable access, to the rocks that form the outcrop. So what's going to happen is the

rover planners are going to put an enormous amount of effort and energy over the weeks ahead, as we're traversing around the outside of this crater, assessing the safety of traversing a slope like that. And then when the time comes, when all of that safety assessment has been done, we're going to have to make some decisions about what we're going to do with this vehicle. Now, if we go in and we try to sample that rock, it's going to have an enormous scientific potential, but it may have some risk as well. And if the decision, as we balance the risk against the benefit, that's a decision that's not made and won't be made for a while yet,

if the decision is to go in, then we're going to have some other things to do first. We went blasting across the plains from Eagle to Endurance very quickly, shooting by all sorts of good stuff along the way. We were eager to see what Endurance looked like, but we're not done with science out on the plains yet. And so if we decide, after weighing the risks and the benefits, to try dipping our toes into the upper reaches of Endurance Crater with the rover, we will almost certainly do some more science out on the plains yet. There's a lot of stuff out there. There's

the wind ripples that we saw out there. There's the fractures that we saw out there, the dimples that we saw out there. There's the heat shield. The heat shield hit the ground not very far from where we are right now, so there's much science to be done. Planetary Radio will be back with much more from Mars in less than a minute. 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, the world's largest space interest group. The Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets. We sponsor the search for life on other worlds, and we're building the first-ever solar sail.

You can learn about these adventures and exciting new discoveries from space exploration in The Planetary Report. The Planetary Report is the Society's full-color magazine. It's just one of many member benefits. You can learn more by calling 1-877-PLANETS. That's toll-free, 1-877-752-6387. And you can catch up on space exploration news and developments

at our exciting and informative website, PlanetarySociety.org. The Planetary Society, exploring new worlds. We're a long way from understanding this. It's like, this is like the mission started over again. Okay, it really is like the mission has started over again. Think back to when we were at Eagle Crater, we're looking off in the distance, there's something cool, we don't know what it is. Let's go there. Well, here we are again. Give us a few weeks. Mars Exploration Rover Principal Investigator Steve Squires, wrapping up his comments about Endurance Crater, the big hole on Mars that has just been reached by rover Opportunity.

To learn more about this new site, we called up planetary scientist Phil Christensen of Arizona State University. One of Phil's specialties is learning about the makeup of geologic formations through a technique called thermal emission spectrometry, or TES, TESS. His instruments on board the spacecraft orbiting Mars allowed us to pick touchdown locations for Spirit and Opportunity that offered hints of past water. Since then, miniature thermal emission spectrometers, or mini-tests, on the rovers have helped guide them to the most promising rocks and formations. Phil, it has been almost exactly a year since we last talked.

You didn't have any rovers on the planet at that point, and now not only do you have rovers, but very, very successful ones. Quite a lot has happened in the last year. It certainly has. A year ago we were hopefully looking forward to maybe getting one rover down, and now we have two that can easily say they've greatly exceeded our wildest dreams. And continue to. But this incredible panorama that came from the Pan Cam, appropriately, of Endurance Crater,

the goal that Opportunity had just reached earlier last week. Yeah, I have seen it, and we've been looking hard at it. As you say, it's spectacular. And what makes it so exciting is the rocks that we can see, the layers in those rocks, the hints of dark-toned rocks, trying to figure out what those rocks are made out of, and then, of course, trying to figure out what process deposited them. The site that we're on has every indication of a lake, and the question is, are those lake sediments that we're looking at in those beautiful cliffs?

Steve Squire has made a point of saying that as we explore this much larger crater, pretty much an order of magnitude bigger than Eagle Crater, where Opportunity got its start, that Opportunity is going to circumnavigate the crater and use all of its sort of long-distance instruments, and he made a point of including, of course, the mini-tests. I guess I should have figured, of course, you've seen the photo photo because you are probably doing that process where you take the images from mini-tests and line them up with the photographic images? That's correct. Ever since we pulled up to the rim, we've been acquiring mini-test data, and we've begun to make exactly what you say, the overlays of the mineralogy that we're deriving from mini-tests

on those panoramic images. We've been working in a couple of modes. One is our low-resolution mode where we try to map the entire crater. And then we've gone back and focused some very high-resolution stairs at a few key points in the crater wall, particularly these places where we see nearly vertical cliffs with exposed rock. We're just starting to get some hints from the mini-tests of the composition of those rocks. Particularly, we're fascinated with some of these dark rocks that look like they have very fine layering in them. It's still preliminary.

The mini-test data are complicated to unravel, but there's hints in those many test data that we're looking at basalt, the volcanic rock that we see all over Meridiani Planum, that maybe those vertical cliffs are made up of basalt. And now the question would be, how did they get there? Tell us a little bit about basalt formations like this. Well, normally the basalt started off life as a volcanic rock. Looking at those pictures, however, the layering is so fine, such small-scale layers, that doesn't look like lava flows or volcanic eruptions. One possibility is that we're looking at ash deposits,

but typically ash deposits, while they come from the same source, magma, liquid rock, they don't have the same minerals in them that a basaltic rock would because the basalt rock cools quite slowly, and the ash basically forms a glass. So what many tests are saying is it doesn't look like a glass. It looks more like a basaltic rock. One possibility is that there were originally lavas erupted on the surface. The wind or maybe even water eroded that, broke the rock up, and transported that material as grains of sand or cobbles into this ancient lake.

And maybe these basaltic sands were deposited in a lake. They may have been just deposited as winds. So my working hypothesis at the moment is that these might be basaltic sandstones that were made of ground-up basalt that was transported and redeposited. Does it tell you anything that, as we also heard Steve Squire say, the floor of this crater is apparently littered with more of those blueberries. It's remarkable. With many tests, it looks as though there's one of the slopes from where we first pulled

up to the rim. If you look around to the right, a slope leading down into the floor is just covered with blueberries. The signature we see in many tests is just virtually nothing but hematite that makes up those blueberries. Other places on the walls leading down in, and particularly on the floor, don't have nearly as many blueberries. So I think one interpretation is that the blueberries are coming from up above, up on the plains, and the winds are blowing them down into the crater. That's important because another possibility would be that the blueberries are weathering out of the rock that we see in the cliffs of this crater.

And if that was the case, one might expect to see blueberries everywhere and maybe even a lot more blueberries on the floor of the crater. So I think these are some of the questions we're going to try to puzzle out. Is the blueberries coming from the plains and blown in, or are the rocks that we see, are they also full of blueberries? Would you agree with Steve that we're almost starting over here, that this terrain, this crater, is so very different from Eagle Crater that it's really almost starting from zero?

Yeah, I would. And as you said, Eagle Crater was very small. We saw one little rock layer, which, as exciting as it was, it was only a few feet thick. Now we're looking at a much thicker stack of rocks, and it's possible that that layer of rock we spent so much time at at Eagle is just the very uppermost layer in the exposed rocks we see. So we've investigated this uppermost layer. Now we have all these other layers beneath it. And that's exactly right. We're really starting over.

The type of questions you can ask are, were all these rocks deposited in water? Or was there episodes of wind that deposited sediments? Are they ash? Are they lava? Are they sedimentary rocks? Do we find hematite all the way through? If all this was deposited in a lake, how deep was the lake?

How long did the lake survive on the surface? So we really can ask just a tremendously larger set of questions with so much more rock to look at. Are you one of those who is hoping that a balance can be found between science and safety and get the rover over to, well, one of the areas that we've heard about is the Burns Cliff? I don't know if that one is going to be easily reachable, but to one of these rocky outcroppings you've been talking about? Absolutely. I think it's too early to talk about if we're going to go into the crater and never come out again. But I think there's a lot of places we can explore around the rim that have a lot of rock. I'm a firm believer that looking at

the rocks is really what we're here to do. And being able to see the rocks in place, in the places they were formed, is really crucial. So I'm hoping that we can find ways to explore those. Maybe, as you say, not getting all the way to Burns Cliff, which is, even for a human, might be a little tricky to get to, but certainly exploring some of these rock outcrops. I hate to give Spirit, on the other side of Mars short shrift because it has been making accomplishments of its own, one of them just being the fact that it's been able to negotiate the much more difficult terrain. And at the press conference, the report from Spirit came apparently from one of your students.

Yeah, it did. Amy Knudsen is one of my students. She's getting a Ph.D. at ASU. Fantastic woman. She's doing a wonderful job. And she's one of five students I've got who have actually been making tremendous contributions to this mission. They've been living in Pasadena, working 18-hour days, really making some important discoveries. And it was great to see Amy get an opportunity to talk to the world

and tell us some of the things that she's been working on. And what she told us about, of course, is that Spirit continues to progress toward those hills, the Columbia Hills. They're now, I guess by now, they're less than two kilometers away. What role is the mini-test going to play on Spirit or continue to play as we reach this new destination? One of the things we're doing as we traverse along, we're collecting routine observations with mini-tests and with PanCAM and the other instruments, not so much in a day-to-day decision-making,

but imagine a geologist on a field traverse on the Earth. You hike across the terrain, and you make notes, and you collect rocks, and you put them in your backpack, and eventually you go back and you analyze them. So what we're hoping is with the mini-test data and the PanCam data, we'll have a treasure trove of information that we can go back and look and do systematic studies of the compositions of the rocks and soils across this wonderful traverse that we're doing. We're also using many tests and pan cams to try to look, always be on the lookout for

remarkable rocks, things that are different. And if they're different enough, we stop and we look at them and we spend some time. So we're sort of the forward reconnaissance eyes of the rover, keeping an eye out for anything unusual. Phil, we're just about out of time, but thank you very much for giving us this somewhat more in-depth look at what the rovers are up to as they continue these incredibly successful missions, and I hope we can check in with you again. Well, you're very welcome, and I'd be very happy to talk to you again. Phil Christensen of Arizona State University is on the science team for the Mars Exploration Rovers.

He is primarily responsible for the mini-tests, the miniature thermal emission spectrometers that are on both of the rovers and have been integral parts of the incredible discoveries that those rovers have been making. And I'll be back with Bruce Betts and what's up right after this return visit from Emily. I'm Emily Lakdawalla back with Q&A. Determining the instantaneous position of a spacecraft doesn't seem so hard, but how do we predict where the spacecraft is going? The position and speed of a spacecraft depends on all of the forces acting on it.

The main force acting on the Voyagers is the sun's gravity and the occasional firings of attitude control rockets, which are necessary in order to keep the spaceship's radio-transmitting antennas pointed at Earth. But there are lots of other forces out there in space. All of the other planets exert their own little gravitational tugs. Solar wind pressure also exerts a tiny force. So far, all of these forces felt by the Voyager spacecraft have had to do with our own solar system. But soon, Voyager 2 is predicted to encounter the heliopause,

often referred to as the edge of the solar system, where our own sun is no longer the most important source of forces on the spacecraft. In fact, by tracking the position and speed of the Voyager spacecraft, we will be able to make our first direct measurements of the forces shaping the interstellar space outside our little solar system. Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Time again for What's Up. We are joined by Bruce Betts, the director of projects for the Planetary Society.

Welcome back, Bruce. Thank you very much. Lots going on in the news, and there must be a lot that's up this week. What's happening? There is. We're going to talk about planets and also stars and comets. It's just a wealth, a cornucopia of goodies in the night sky. Look up there in the night sky shortly after sunset.

Look over in the west and you will continue to see the very, very bright Venus. Now looking this week, you'll also see right near it another star. That is Beta Tauri. And Beta Tauri is about the same brightness right now as Mars is, which is to the upper left of Venus. Mars will be roughly equidistant in between Venus, the extremely bright Venus, and the not as bright Saturn compared to Venus, and then Mars dimmer in between. You look up there and you're wondering what's going on. That's what's going on. Keep looking farther towards the east across the sky almost overhead, and you'll see very bright Jupiter.

We've also got two comets, which are going to be challenging for city dwellers but still visible, technically naked eye, but I think you're going to have to be out in the dark places to see them that way. We have comet NEET, technically C-2001Q4 NEET, that is up in the evening now, and you can look kind of in the southwest. And if you look about a fist width, if you take your arm and stick it out and look at the width of a fist from Sirius. Make sure no one's face is in the way, but put your fist out there as far as you can reach. From Sirius, the brightest star in the sky, look up above that at sunset. And if you see a little fuzzy patch, that is probably this comet NEAT. Binoculars

will be very, very helpful to look for this. And if you go to our website, planetary.org slash radio, look at this week's show, and we'll give you a link to where you can find out more information about how to find not only comet NEAT, but also comet LINEAR that is up in the pre-dawn skies. And it's also somewhat dependent on your hemisphere as to exactly where you're looking and how good your view will be. So come check in with us. Check out comets. You mentioned these comets last week. You said that they're going to be visible for a while.

Are they becoming a little bit easier to see as time goes by? Yes, but it's variable, and it's kind of changing. They're getting easier, like in the case of NEET in the night sky, but then not necessarily getting brighter at the same time. So it's tricky. Let me mention, too, for those of you who aren't common comet gazers, comets, even if you get a very good view of a comet, and we had very bright comets a few years ago, typically they appear as a fuzzy patch in the sky,

especially unless you're in the middle of a very, very dark area. It's just a fuzzy patch in the sky, especially unless you're in the middle of a very, very dark area. It's just a fuzzy patch in the sky. They are not moving quickly, despite what cartoons show. They do not go streaking across the sky. But you can watch them move from night to night. There is a pretty big variation in where they are each night in the night sky compared to, say, a planet in the night sky. Now, is this a situation where somebody with a telescope really doesn't have a big advantage over someone with that pair of binoculars you mentioned? Yeah, the binoculars are almost your best thing for looking at these comets because they give you a nice wide field

of view while also magnifying thing and they collect a lot of light for you. And that's what you're looking for in the case of these comets, being able to see them better. And again, if you're in a nice dark place, then you may get a shot at seeing the tails going out. What else do you have for us? Well, let's go on to this week in space history. On May 14, 1973, Skylab was launched. Nice, the U.S.'s first space station. You know the thing that I thought was the coolest thing about Skylab?

What was that, Matt? That jogging track that they could run around and the force of them running would keep them on the inside wall of Skylab. That was cool. It was like a hamster. That was very cool, and provided some very nice videos as they wiped out, too. That was a good time. All right, on to Random Space Fact!

Hey, Matt, if you weighed 100 pounds or 100 kilograms on Earth, which are you closer to? Skip that. Anyway, you would weigh at the cloud tops of Jupiter 236 kilograms or 236 pounds, depending on which units you're using due to that higher gravity. Now, it would be awful tough to stand at the cloud tops of Jupiter, so that's a fairly pointless fact, but that's why we call them random space facts. On to the trivia contest, Matt. Last week, we asked people how many people flew to the moon twice. This would include either just going around the moon, orbiting the moon, or going to the surface of the moon. I'm sorry.

There were three people. We want to know who were they. Who were they, Matt, and how did people do? They were, and a lot of people got it right. They were James A. Lovell, Jr., John Young, and Eugene Cernan. They didn't all get to walk twice on the moon, but they did go. They did swing around the back there. No one got to walk twice.

That's true. Nobody actually went down and walked twice. John Young and Eugene Cernan did get to go visit and then go back and actually walk on the surface. Lovell, of course, was scheduled to, but that whole pesky Apollo 13 incident kept him off the surface. Lots and lots of people got into us with the right answer this week. And the winner is Kathy Preby. Kathy Preby, almost a local, Lancaster, California, just a little ways out there in the desert. The sometimes home or near it of the space shuttle. Kathy is going to be getting one of our Planetary Radio t-shirts. Congratulations.

Yay! What do you got for us this week? Well, if you'd like to win one of the glorious Planetary Radio t-shirts, then you can try to answer this question. I'm going to give you an easy one this week. Try to get lots of entries, have some fun. What moon in our solar system has the thickest atmosphere? What moon in the solar system, what satellite orbiting a planet has the thickest atmosphere? What should people do if they think they know the answer? Go to planetary.org slash radio follow the instructions to enter our contest and win the lovely Planetary Radio

t-shirt where you'll learn that if you give us 30 minutes, we'll give you the universe. And I think we're done. We are indeed. We are done. I'd like to encourage everyone to go out, look up in the night sky, and think about radio waves permeating your brain. Thank you, and good night.

That's something we can help with. This has been What's Up with Bruce Betts, the director of projects, who joins us each week here on Planetary Radio, and I'm pretty sure he'll be back next week. You going to be back next week? I hope so, Matt. I hope so, because I look forward to this more than really anything else in my life. That's not

true. Thank you. Good night. We're out of time for this week. Join us again next time for another adventure in the cosmos. Thanks for listening.