Planetary Radio: Space Exploration, Astronomy and Science - Phil Christensen Explores Mars in the Infrared

Episode Date: May 26, 2003

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This is Planetary Radio. about the final frontier. We're glad to have you with us this week. Sometimes it's what you can't see with your own eyes that changes the world. In this case, the world is Mars. We'll talk with Phil Christensen, a planetary geologist who has devoted much of his life to studying not just the red, but the infrared planet. Later, Bruce Betts will be here with What's Up and the new trivia contest. First, though, here's Emily trying not to get caught in a flash flood on Mars. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked,

Given the planet's very low atmospheric pressure, how could enough water have existed on Mars to create a flood? There are two major types of Martian channels, both of which were most likely formed by water. There are two major types of Martian channels, both of which were most likely formed by water. There are two major types of Martian channels, both of which were most likely formed by water. The most dramatic channels, called the outflow channels, have features similar to those found in catastrophic flood channels on Earth like the channeled scablands in Washington State.

The amount of water necessary to produce the Martian catastrophic floods is estimated at about 10 to 100 million cubic meters per second, a flow about 100 times greater than the flow from Earth's largest river, the Amazon. All of this water most likely came from beneath Mars' surface. The temperature and pressure at the surface are too low to allow liquid water to survive long before vaporizing. But conditions underground include higher pressures and temperatures, probably warm enough for water to exist

as a liquid. How could this water come to the surface to start a flood? Stay tuned to Planetary Radio to find out. Dr. Phil Christensen is the Cork Professor of Geologic Sciences at Arizona State University. That's also where he heads ASU's Mars Spaceflight Facility. And if you pick up a copy of the Planetary Report, the May-June issue of that magazine, which is just about to appear, you'll find an article by Dr. Christensen and a grad student. I take it you're a grad student, Matthew Schindel? Yeah, he's an interesting kid. He did biology, poetry, and now planetary science.

Well, good for him. He's a writer and a scientist. And a scholar and a gentleman. Dr. Christensen, I take it from this little preview of the article I've seen that you sometimes are a little bit envious of Earth geologists. Absolutely. I started life as an Earth geologist, and the thought of having a question and actually being able to get in a Jeep

and drive out and poke around and break a rock and study that question brings back fond memories. I mean, to study Mars, it's a decade between an idea, an experiment, to when you finally get the data back. Tremendous fun, but it's definitely a slow process to explore that planet. So have you and your colleagues had to sort of, for lack of a better term, had to invent the field of optical geology? I think that's a fair statement, especially infrared. I did my graduate work on the Viking project with Hugh Kiefer, and literally Hugh was pioneering

the idea of looking in detail at planets with infrared eyes. And I looked at the literature, and there was virtually nothing being done with infrared spectroscopy, high-resolution infrared imaging. So we have literally invented a field over 20 years. It's been tremendous fun. I mean, you never know. The beauty of looking at Mars with infrared data is you never know quite what to expect. And I don't think we ever said that the title of the article in the Planetary Report

is exactly what you're talking about, Mars Infrared. It's been fun. It was a totally unexplored field when I started, so we've been feeling our way through. Over the years, we've gone from having just a reconnaissance, low-resolution view of Mars to now we're literally taking infrared pictures with the same resolution of the Viking cameras that we're taking in the visible. We can see things the size of a football field.

That was unheard of when I started doing this back in the Viking era. Now, I take it that you've had infrared instruments on both the Mars Global Surveyor and the newer orbiter, the Mars Odyssey? That's correct. I actually go back even a little further. The experiment on Mars Global Surveyor was actually originally, I proposed it for the ill-fated Mars Observer. Oh, yes.

So we have somewhere floating around the sun is a perfectly nice infrared spectrometer that we never got to use. Yeah, we have a couple orbiters, a couple instruments on a couple orbiters. Together they make a wonderful pair. One of them has the first one that we flew on on Global Surveyor, has really low resolution, spot size, a pixel on the ground, is several miles in size. But it has wonderful spectral resolution. We measure about 150 different wavelengths of light. And then the later instrument, the Themis experiment on Mars Odyssey, is the exact opposite. It has only a few filters, only a few wavelengths, but it has exquisite resolution that we can, you

know, have 100 meter per pixel images. So the two together are really giving us a very powerful tool to explore Mars. And they do work hand-in-hand then? They do. It's funny, they weren't intended that way. The way these projects work, they're very competitive. You propose an experiment, you go up against a lot of other experiments. But the fact that both of them are there, and we've had the tremendous luck of having them both still working, we really are mapping, and we can map Mars two different ways and use the data together. And it really is a case of where the two instruments are much more powerful together

than either one of them by itself. There's an incredible number, partway through the article that you've done for Planetary Report, about the mapping that you have done with the instrument on the Mars Global Surveyor, the one that has a little bit wider view. 91,572,072 signatures. What does that actually mean? Each one of those is a complete infrared spectrum. Imagine taking infrared light, which is just like visible light,

except your eyes can't see it. We can build an instrument that can see that. We break that up into 150-odd wavelengths. Each one of those observations is an infrared spectrum. Each one has a tremendous amount of information about the composition of the minerals on the ground, the gas and dust and water in the atmosphere. Each one of those, 91 million, is almost a little story in and of itself of this is what Mars is like at that spot on the ground.

I also learned from your article that the Mars Exploration Rovers, which, with any luck, are going to be launched for the Red Planet next month in June, also carry a version of this infrared spectrometer. They do. Over the 15 years since we first started, we've been able to miniaturize this spectrometer. So now instead of being the size of a large mailbox, it's more the size of a shoebox or smaller, small shoebox. So we have one on each of the rovers.

The idea with all of these is again to try to figure out looking at the infrared signature what minerals are present. So the rovers we've used the orbiter instruments to map the planet and find some really exciting places with some intriguing minerals. We're going to land on the ground and the first thing these rovers will do is we'll scan around and make a complete panorama of infrared spectra with this miniature version of our instrument. And now that will tell us the minerals that are in each rock. If you remember back to the Pathfinder rover, it takes a long time to drive over and position the rover to where it can study a rock in detail, we

expect to land, look around, see hundreds of rocks. So what the mini-tests will do is tell us which rocks are the most interesting, which have the key minerals or the most interesting minerals, and so the rover can go over and explore those and not have to just randomly wander from rock to rock. Before we take a break, and when we come back from that break, I very much want to talk about what you have learned from these instruments so far, and you've learned quite a bit. Apparently the site, the landing site for one of the Mars exploration rovers,

was chosen in part because of some of the data that has come back from the Mars Global Surveyor? That's absolutely right. because of some of the data that has come back from the Mars Global Surveyor? That's absolutely right. The infrared spectrometer on Global Surveyor, we detected a unique mineral. That was its job. That's why we sent it, and it did its job beautifully. And so we found an intriguing place that the first time, really, we're going to send a rover to Mars or a lander to Mars based on what

minerals are present, some of these more sophisticated techniques for mapping the surface, rather than just the pictures that we acquire. So I'm extremely proud. I mean, it was a great experiment, and it's found a fun place for us to go explore. We're talking with Dr. Phil Christensen of Arizona State University, and his optical geology of Mars, the red planet, which is underway with a couple of orbiters and will be expanded with the arrival, we hope, of the Mars Exploration Rovers in the very beginning of 2004.

We'll continue our conversation with Dr. Christensen 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,

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The Planetary Society, exploring new worlds. We're talking with Dr. Phil Christensen. He is the Korek Professor of Geologic Sciences at Arizona State University. We're talking about Mars, something he has paid a lot of attention to and has a couple of instruments circling the red planet right now. With all kinds of interesting data coming back, we've talked about those instruments and how they work. But now let's talk, if we can, Phil, about what you've started to learn.

And I take it we've learned quite a bit. We have. First of all, Mars is a fascinating place. And secondly, looking at it as we've done sort of a new way with these infrared instruments, we have learned a lot. For me, one of the most exciting things we've learned has been mapping the composition of the surface, the rocks and minerals, and really looking for unique places, places that are different from most of Mars. We really didn't know what to expect when we went there. It turns out that it's what I would call a volcanic planet. The minerals and the rocks look like they're mostly volcanic minerals, volcanic rocks. They've obviously been eroded and transported and blown around,

but the basic composition of those rocks is volcanic, except for a couple of really, really remarkable places, one of which, a place called Sinus Meridiani, is the target for one of the upcoming Mars rovers. What that place has, what Meridiani has, is a mineral called gray hematite. You can actually buy little chunks of hematite, polished pieces, in most rock shops or novelty shops. And what makes it exciting is we think hematite most likely formed in water. Those who are looking for interesting places on Mars,

a place where water was present for a long period of time is always at the top of the list. In fact, this hematite is so prevalent in the area it's actually sometimes called the hematite region? It is. And, I mean, that's really what sets it apart. Many people are familiar with hematite. Another name for a form of hematite is rust. The red hematite is actually what gives Mars its red color, but that's not what we're talking about.

This is a different kind of hematite. If you held it in your hand, it looked gray. It takes much more water to form the gray hematite than what gives Mars its red color. We think, I think, for example, that water was probably present at this hematite site for hundreds, thousands, maybe tens of thousands of years. There is, in spite of this evidence of water on the surface of Mars, and even some evidence of water recently on the surface of Mars, it's still a very, very dry place in most areas, isn't it?

That's absolutely correct. And part of the enigma, part of the beauty of this, most places you look, Mars is cold and dry and frozen. It might have a lot of water, but it's probably in the form of ice, maybe snow, maybe glaciers. So the image that you should have of Mars is this cold, frozen place. And yet, in a few spots, like this hematite site, it really looks as though there was warm water there, quite a bit of warm water and for quite a long time. Again, that's what sets this place apart.

That's what makes it so interesting to go and land and say, okay, why is this one place on Mars so different from the cold, frozen planet that we see everywhere else? One of the other areas that your instruments have taken a look at are the poles of Mars, where one can find some water in there with the frozen carbon dioxide, the dry ice. Have we learned more about those polar caps? Absolutely. The Odyssey has an experiment called the gamma ray and neutron spectrometer that have measured the signature of hydrogen directly, which we think comes from ice and water.

The camera, the visible camera that we have on the Themis experiment, in addition to looking at infrared images, we also take visible images, and that has revealed some deposits, which I believe are snow, dusty, you know, dust-covered snow, but snow banks that actually melt and may be responsible for these very young gullies that were one of the most remarkable discoveries that we've made in the last five years. People have been trying to explain the origin of those gullies, and I think one possibility is that they form from melting snow.

And again, what's so intriguing is that we see what look like patches of this snow that are still present on the surface today. What are you hoping to learn? What questions would you most like to see answered, and might have a reasonable chance of having answered, by the Mars Exploration Rovers? As a geologist, what I love is the question of what happens? What's the history? What's the story?

I look at a landing site or any place on Mars, and I just think a rock sitting on that surface has seen billions of years go by. What has been the story of that site? So for me, what's the history? How much water? When was it there? How long was it there? Was there any life in that water or life that could have survived in that water? It really is just the history of that place.

But clearly, for many people, myself included, the role of water, the possibility of life, that's what makes both of the MER sites, the Mars rover sites, particularly exciting. With all of these technological wonders, these marvelous instruments, I wonder, would you still trade it all for a couple of days up there with a shovel and a hammer? Absolutely. I've spent my entire career sending robots to Mars, and I've had a fantastic time doing it.

We've learned unbelievable things. In one day, hiking around with a rock hammer and a magnifying glass and a bottle of acid and just the things a geologist carries with them, you could answer many, many of these questions. I mean, for example, these snow deposits land, stick a shovel in the ground, and within seconds you'd know if it really was snow under that thin layer of dust or not. you'd know if it really was snow under that thin layer of dust or not. Take a rock, crack it open with a hammer, look at it with a magnifying glass. You'd know instantly, is this a volcanic rock or a sedimentary rock?

Doing things with robots is a challenge. It might take a couple of days just to get over to one rock and look at it. A geologist could do that in 30 seconds. It's what we have. It'll be incredibly fun. But someday I'd love to see geologists and scientists walking on the surface. You and me both. With only a minute or two left, we should give you a chance to give some credit elsewhere.

I know that you are listed as the designer of the instruments that we've talked about on the Mars Global Surveyor and the Mars Odyssey Orbiter. But I know that you've got a team that you work with and a number of students. It's a fantastic team. I've had the great luck of sitting down and going, what if we could do this, and could we make one of those, and worked with a group of engineers at Raytheon in Santa Barbara, incredible bunch of people, most dedicated people I've ever met. At Arizona State alone, we have a staff of about 50 people to run these experiments, everything from programmers, scientists, engineers,

artists, and then I have 10 graduate students and undergraduates. It's a wonderful group of people. I love going to work every day just to interact with them. Recently, we've been trying to do a program where we're actually involving high school and middle school kids in these projects and trying to expose them to not just the information but the actual excitement of exploring themselves. What a great opportunity for very young people to do real science.

It is. We let them, they have to write a proposal just like a scientist would, and then we let them take a picture. They have to propose a question, and we let them actually point the camera and take a picture of anything they want, it's so much more effective than just expecting them to memorize some things. Watching them in action, it's unbelievable the curiosity and the excitement and the energy that these kids bring

when you actually let them explore on their own. Phil Christensen, we are out of time. I want to thank you very much for joining us for a few minutes on Planetary Radio and wish you continued luck. Thank you very much. Phil Christensen is the Korek Professor of Geologic Science at Arizona State University. He heads ASU's Mars Spaceflight Facility and is also the designer, principal investigator, and is also the designer, principal investigator,

of those thermal or infrared spectrometry instruments that are circling Mars right now, with another one, a miniaturized one, about to head for there on the Mars Exploration Rovers. If you'd like to learn more, visit the homepage for this week's show at planetary.org. You'll find links to Phil's Mars Spaceflight Facility at ASU, as well as several other relevant sites. We'll sit down with Bruce Betts in just a minute. Is Emily still running from those floods? I'm Emily Lakdawalla, back

with Q&A. What could have caused the catastrophic floods on Mars? Here's one scenario. Some tectonic event could force the planet's surface to tilt, just as rock layers on Earth are tilted by the motions of its plates. This event could cause a once flat reservoir of water to tilt also. Gravity would then pull the now higher areas of water against the lower areas. With enough water, the pressure could be large enough to break through the surface and catastrophically release the reservoir of water. Even with current climate conditions, the billions of cubic meters of water that was released

could travel for hundreds of kilometers before it boiled away. This is a nice theory, but no one knows for sure if such underground reservoirs of water exist on Mars. That's why the European Space Agency has equipped the Mars Express spacecraft, due to launch June 2, with a radar-sounding instrument called Marsis. Once Mars Express settles into its orbit in 2004, Marsis will use long radio waves to penetrate the Martian surface to a depth of 2 to 5 kilometers, looking for radar echoes from underground reservoirs of liquid or solid water. 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. Well, it's not a garden spot. It's just Bruce Betts' office. But it's going to be a fine place for us to learn what's up. Hi, Bruce. Hi. It is on several tours of the Pasadena area, however. Anyway, hi, Matt. I'm sort of medium happy to be here today.

Oh, well. No, I'm looking forward to being extremely happy by the end of this episode. We're going to cheer you right up. Thank you. Let's get started. What's up this week? Well, we've got the five naked eye planets coming back, naked eye once again, but you're going to have to strain for Mercury. It's low, low, low in the morning sky in the east near Venus, below Venus.

If you have a very clear view to the horizon, you can see it right before dawn. Mars is getting brighter and brighter in the southeast. You can see it any time before dawn. Jupiter in the evening, brightest thing overhead. Saturn getting kind of low in the west, southwest in the evening. On to this week in space history. Matt is making me admit to all of you, I had to write it on the blackboard a hundred times as well,

that last week I gave an error in this week in space history. I even read it correctly, but I gave you something for March 23rd instead of May 23rd, the first flight of Gemini 3. So, 50 lashes with a wet noodle for me. This is not a mea culpa. This is a mea culpa. This is a hea culpa. He is forced a hea culpa. This is a mea culpa. This is a hea culpa.

He is forced to hea culpa on me. But then I didn't catch it. Not that you caught it. You said March 23rd, and I didn't catch it. I wasn't paying any attention, so sorry about that. Anyway, we'll come back to Gemini 3 in our trivia contest. Right now, let me tell you what happened this week. May 30th, 1971, Mariner 9 was launched. Mariner 9 was the

first Mars orbiter. Its sister craft, Mariner 8, ended up exploring one of Earth's oceans. Mariner 9 ended up teaching us all sorts of things about Mars. Much more encouraging picture of Mars than we had had up until that date, right? Funny you'd mention that, Matt. On to random space fact! Mars looked like a dead world, heavily cratered only, as seen by Mariner 4, 6, and 7, the first flybys of the planet. By chance, we had seen only the ancient southern highlands of the planet, at least basically. Only when Mariner 9 got there in 1971 and went into orbit

did we see the spectacular volcanoes, canyons, and geologic diversity of the planet. And Mars got very interesting once again. Very good. Before we go on to trivia, any news? Anything to share? There is some news. There is some news. There is a spectacular image taken by the Mars orbiter camera,

not of Mars, but doing the first astronomy of other planets from Mars. They used the telescope on the Mars Global Surveyor spacecraft to look both at the Earth-Moon system, a picture of our home system, and also to look at Jupiter, and it captured three of Jupiter's moons as well. And it's really quite impressive and gives you, once again again that feel for our profound place in the universe. Yeah, I said to someone else up here, I said, you know, it's a little bit larger, pale blue dot, but it's so cool to see this image. It's not like the prettiest picture of Earth ever taken, except that maybe it is in context.

It's one of the most profound. Go to planetary.org. There is a headline about this, and it will lead you to more of the pictures of this. And that leads us right on to the trivia. Let's try last week's question first. All right, last week's question. Who was the first person to travel in space twice? There was a little bit of a trick to this, but not too much.

Well, just because last week Matt really wanted this person to be in orbit. First one was a suborbital flight. It was the U.S. astronaut Virgil Gus Grissom, who flew on the second flight of a U.S. spacecraft into space, and also on Gemini 3 of the failed This Week in Space history

but very successful mission into space. Gus Grissom, first person to travel in space twice. Did anyone know this out there? Yeah, actually. Oh, thank goodness. Quite a few. Not quite as high a percentage got this right as we normally have. But a lot of people did get it.

But we still love you. Don't turn off the radio. We have this one. Now, this was not the winner, but I wrote back to him and I said, this was so cute that we had to mention it. Matt Brown, Matthew Brown, good name anyway, out of not the winner, but I wrote back to him and I said, this was so cute that we had to mention it. Matt Brown, Matthew Brown, good name anyway, out of Chicago, Illinois. He did have the right answer. Matthew, you weren't the one randomly chosen, I'm afraid.

But he did remember that we're now giving away the 3-D poster of Mars. And he said, could he have a life-size poster of Mars, if that wouldn't be too much trouble? It's too much trouble, but thanks anyway, Matthew. Thanks for asking. Now on to our winner. And here it is. Our winner this week, Donald L. Webb, Jr. of Troy, Michigan. Got the answer right. Virgil I. Gus Grissom. Congratulations, Donald. You'll be getting that poster. Thank you very much. And now on to this week. As you may be aware, or may not be aware, one interesting thing about planetary nomenclature is there are all sorts of rules for planetary nomenclature,

especially things named in the days of spacecraft. So for the planet Saturn, it's moon Tethys. What are its features named after? So there's a theme here. There's a theme. There's a theme. All features on Tethys, what are its features named after? So there's a theme here. There's a theme. There's a theme. All features on Tethys, which at this point has just been observed by the Voyager spacecraft. What are its features named after?

What's the theme? So craters, mountains, that kind of stuff. That kind of stuff. Excellent. Okay. How do people enter? Go to planetary.org, follow the links to Planetary Radio, and you'll be informed as to the super-secret,

tricky way to enter our trivia contest. That's it. We're out of time, Bruce. Thanks again very much. Thank you all, and look up in the night sky and think happy thoughts. Thank you. Good night. Bruce Betts is the Director of Projects for the Planetary Society. He joins us each week for What's Up. We'll be back next week with another new show. All of us at Planetary Radio hope you'll join us then and wish you the best.