Planetary Radio: Space Exploration, Astronomy and Science - Celebrating the MESSENGER Mercury Flyby With Sean Solomon

Episode Date: February 11, 2008

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Mercury, up close and personal, thanks to Messenger, this week on Planetary Radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. Messenger mission leader Sean Solomon is back. We last talked to him just before his spacecraft reached our solar system's innermost planet. Now he'll share some of what we have already learned

from that first thrilling flyby of Mercury in more than 30 years. But that's not all. We're just around the corner from another Bill Nye commentary, this time on the current mission of space shuttle Atlantis, delivering a package from Europe to the International Space Station. And Bruce Batts will prepare us for a total lunar eclipse that is just days away.

He's on top of a lot more going on in the night sky this week, and he'll help me give away another Planetary Radio t-shirt in our weekly space trivia contest. Emily Lakdawalla is off this week. She'll be back with a brand new Q&A segment next time. Speaking of Atlantis... T-minus 10, 9, 8, go for main engine start, 7, 6, main engine ignition, 4, 3, 2, 1, 0, and liftoff of space shuttle Atlantis as Columbus sets sail on a voyage of science to the space station. The shuttle made it off the pad on Thursday, February 7.

As we put this week's show to bed, Atlantis had docked at the International Space Station, and astronauts were preparing for a delayed first spacewalk. That delay is something of a mystery. NASA spokespeople admit that a crew member has had some sort of non-life-threatening medical problem, but so far they won't say which crew member or what the problem is. There's been a change of personnel for that spacewalk, which will install the European Space Agency's Columbus Lab. Bill Nye will tell you more in a minute. The Bush administration came out with its budget

request for NASA last week. It calls for an increase of almost two percent, with about a quarter of the 17.5 billion dollars going to science missions. That includes funding for two new Earth-observing birds that will monitor climate change, and a major mission to the outer planets that is yet to be identified but could be a Europa lander. Sadly, Mars exploration doesn't do as well. The details are at planetary.org. I'll be right back with Sean Solomon. Here's Bill. Hey, hey, Bill Nye, the planetary guy here, vice president of the Planetary Society. This week, I'd like to discuss briefly a new thing in low Earth orbit. Space shuttle Atlantis departed on STS, Space Transport System Flight number 122,

carrying with it what is considered the first European spacecraft. That's right. The European Space Agency's Columbus Laboratory is considered a manned spacecraft, human spacecraft. It has a couple of European astronauts on board. It has its own life support system. It attaches to the International Space Station by means of Node 2, which has a much more romantic name, Harmony. And it's orbiting the Earth. And the European Space Agency has a couple of astronauts up there.

And they're going to do some traditional low-Earth orbit experiments. And you say, well, this is no big deal. Well, listen, my friends, this is international cooperation. I remember when I was at the Johnson Space Flight Center back in 1996 walking around. And these modules were gleams in engineers' eyes. They had mock-ups and stuff. Well, it's a remarkable thing because we are maintaining a presence in space, not just with the National Aeronautic and Space Administration, NASA,

but with the European Space Agency. This is truly international cooperation as we make sure we know how to live and work in space so that we can, dare I say it, go one day to Mars and look for signs of water and life. To continue our exploration of the solar system so that we can understand our world that much better. Thanks for listening to Planetary Radio. I'll talk to you next time. Bill Nye, the Planetary Guy. Barely a month has passed since our last conversation with Sean Solomon.

Back then, we wished the Messenger mission principal investigator the best of luck and held our breath. Days later, on January 14, Messenger did exactly as it was supposed to do, coming within just 200 kilometers of a planet that had not been visited since Mariner 10's last flyby in 1975. The probe will repeat this performance in October of this year, and then one more time before it goes into orbit around Mercury in 2011. I found an elated Sean in his office at the Carnegie Institution of Washington, where he directs the Department of Terrestrial Magnetism. The past president of the American Geophysical Union, is also a member of the National Academy of Sciences, and has worked on several other robotic missions. And in case you

forgotten, MESSENGER stands for Mercury, Surface, Space, Environment, Geochemistry, and Ranging. Sean, we are so glad to have you back. I saw a quote on your website from Bob Strom, the only member of your science team who was also on the Mariner 10 science team, and he basically said, these images of Mercury that Messenger has sent back to us are so good, even the parts of Mercury that we've seen before up close, thanks to Mariner 10, are brand new to us.

It's been a terrific experience, Matt. The flyby from a technical point of view was near perfect. We hit the trajectory we wanted to hit, so we're en route to further flybys. All of the instruments operated as planned, so we have a beautiful data set. As you mentioned, the imaging system worked spectacularly, and it was, as an aside, it was a delight to watch Bob Strom. He was sitting in front of monitors as the new images came up, and he was sitting next to grad students who were maybe 50 years younger than he was, and he was as excited as anyone in the room.

So it's a measure of the quality of the data that have come back. It's beautiful data set, not only for imaging, but for all the other instruments. And, of course, the images always get all the attention, at least from the public. But let's start, because of that, with some of the data. I also saw, and we'll put a link up to this, there is a truly beautiful animation that someone did of your spacecraft flying through Mercury's magnetosphere, and as it goes through this field, there is a graph that is synchronized to the animation and shows the variation in that field, and it really makes for pretty interesting viewing.

It's a terrific animation. It was done by some colleagues at the University of Michigan who provided one of the sensors on one of our spectrometers, the Fast Imaging Plasma Spectrometer built at the University of Michigan. It measured for the first time plasma ions, both electrons and protons and heavier ions near Mercury, and showed us that the magnetosphere of Mercury is full of plasma ions and that the data are going to tell us a lot about the interaction of the solar wind and the plasma that streams out from the sun with Mercury's small magnetosphere.

Mercury's got the most Earth-like magnetosphere in the solar system, but it's a miniature version. We owe our lives in many ways to our magnetosphere because it forms a protective bubble that shields all life on the Earth's surface from energetic cosmic rays from outside the solar system and from the sun. So understanding our own magnetosphere is an important goal in Earth science, and to be able to study the best analog in the solar system of the Earth's magnetosphere gives us a special opportunity. Well, we will, as I said, make sure that link is up from planetary.org slash radio. And, of course, it's on your website as well, the main website for Messenger.

And we'll have a link to that, too. How about Mercury's tail, which I guess you also got a much better look at than has been done previously? Yes, Matt. Mercury has two kinds of tails. It has a magneto tail, which we flew through. That's the anti-sunward part of the magnetosphere. But it also has a tail of neutral atoms that are streaming away, again, opposite to the direction of the set of loss processes for a very dynamic but very tenuous atmosphere, which is continually changing. It has to have continuous resupply to balance the loss. But we were able to take images at wavelength sensitive to two of the species in Mercury's tail,

sodium and hydrogen. And that was the first time that was done. And, of course, our images are at very high resolution compared to anything we can do at Earth. The fact that we were able to combine the two will give us some leverage in understanding the mechanisms for energizing atoms in Mercury's atmosphere or atoms in Mercury's surface and what it is that makes that tail continue to be present and continue to change.

We do expect that the next time we fly by Mercury, the tail is going to look a little different. So we're eager to be able to get a better understanding of the processes that govern that interesting part of the Mercury system. Why would you expect the tail to be different for the next flyby, which is coming up in October? We expect that the activity of the sun is a very important regulator on Mercury's magnetosphere and atmosphere. We expect that the magnetosphere and atmosphere are strongly coupled. For one thing, the magnetosphere and the interplanetary magnetic field of plasma interact very, very strongly. And one of the leading ideas for generating species in Mercury's atmosphere

is that from time to time the solar wind ions can impact directly onto Mercury's surface and sputter atoms off the surface that then are added to the atmosphere. These atoms can be so energetic that they quickly find their way to the night side and in some cases into the tail. We are just beginning a new solar cycle. When we visited Mercury January 14th, the sun was extraordinarily quiet. But throughout the rest of the MESSENGER mission, the sun is going to become more and more active. So there's a good chance that even at the next flyby, we're going to see a more active sun than in January.

We're going to see a different snapshot of the dynamics between the activity of the sun and the activity of Mercury's coupled magnetosphere atmosphere surface. So we're eager to watch the entire system change, and we hope to learn quite a bit more about those interactions as those changes are monitored. Nice of the sun to act as part of your science team, an active participant in these experiments. It's terrific. There's actually another way that we benefit by having an active sun. One of the geochemical remote sensing

instruments we carry on board is an x-ray spectrometer that looks at the surface and looks at x-rays that come off the surface as a result of a fluorescent process responding to solar x-rays. We also have a monitor that looks through our sunshade at the sun to see what the solar x-ray flux is doing. So as the sun becomes more active, there's more X-rays hitting the surface. There's more of a signal that we can use to map the chemical composition of Mercury's surface and how it varies across that surface. That's Sean Solomon. As principal investigator, he leads all aspects of the MESSENGER mission to Mercury,

which made its first flyby on January 14. I'll return with Sean in a minute. This is Planetary Radio. Hey, hey, Bill Nye the Science Guy here. I hope you're enjoying Planetary Radio. We put a lot of work into this show and all our other great Planetary Society projects. I've been a member since the disco era. Now I'm the Society's Vice President.

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Here's how to find out more. You can learn more about the Planetary Society at our website, planetary.org slash radio, or by calling 1-800-9-WORLDS. Planetary Radio listeners who aren't yet members can join and receive a Planetary Radio t-shirt. Members receive the internationally acclaimed Planetary Report magazine. That's planetary.org slash radio. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. My guest is Sean Solomon, principal investigator for the Messenger mission to Mercury, which just made its first flyby of that planet, giving us the first close-up view in 33 years.

We're going to talk about the spectacular images that have been returned, including photos of spidery fault lines emanating from the center of a huge basin. But first I wanted to ask Sean to tell us more about Messenger's ability to analyze Mercury's chemical makeup. That's where I was going to go next, actually. Have you had any luck so far in figuring out some of the elemental composition of that surface of Mercury, which is also something that your instruments are designed to do? They are. That's one of the long-term objectives of our mission,

is to try to sort out the chemical composition of Mercury's crust, because it tells us an enormous amount about how Mercury got put together and how it ended up with this proportionally huge metal core that is required by the high bulk density of Mercury. And the answer is that the flybys are a really tough time to do that analysis. The geochemical remote sensing instruments that we carry are counting very scarce gamma rays and X-rays and neutrons coming off the surface. And we flew by in January at about six kilometers per second past the planet. And there just wasn't a lot of time that we were within range. Each flyby now is slower than the one before because we've taken energy out of the orbit. So we'll have a better chance in subsequent flybys to gather more data that

will be sensitive to the chemistry. But we're really looking for the orbital phase to do the detailed chemical mapping, because then we're continuously in orbit around the planet, and we're gathering data all the time, and we can integrate over an extended observation period. So I expect that some of the answers to questions we are going to Mercury to answer will have to wait for the orbital phase. Let's turn to those beautiful images of the surface, which have been getting so much good press. And can we start with this region called the Caloris Basin,

which, of course, is one of those areas of Mercury that we did have a bit of a look at from Mariner 10 all those years ago. But your pictures are a little bit sharper. They are sharper, and we're seeing the basin for the first time in its entirety. Mariner 10 showed us some beautiful images of a little less than half of the basin. They were at low sun angle, so you could see a lot of the deformational features on the surface. We flew by, and the sun was high overhead. First of all, the basin is bigger than we guessed from Mariner 10. It's more than 1,500 kilometers in diameter. It is one of the youngest and best preserved large impact structures on Mercury, or in fact,

anywhere in the solar system. What we saw is that the floor of the basin is brighter, has a higher albedo than the surrounding terrain, which is hinting at different composition, although that remains to be worked out quantitatively. We saw right away that there are younger craters that impacted that floor material and excavated darker material that we can see as a halo of darker material around these young craters that impacted that floor material and excavated darker material that we can see as a halo of darker material around these young craters that sit on the floor. That suggests to us that there's a kind of layering beneath the surface and some different material differing in composition and that a big enough crater can excavate down to see

that different material. We have some windows into the third dimension in Caloris, and of course that basin itself is a huge window into the deep interior because when it formed, it excavated tens or maybe even a few hundred kilometers into the interior. So there's a chance that careful analysis of the rim material, even some of the ejective material may be telling us something about quite deep inside the planet. On top of that, we've known since Mariner 10 that the floor of Caloris has concentrated several episodes of deformation, faulting, of different types. The earliest faults represent a contraction that produces a grid of wrinkled ridges on the floor. And then

sometime later, we don't know precisely how much time later, the floor was under extension. And instead of ridges, the fault features produced troughs as the floor was stretched horizontally. So it's been quite a challenge to understand the processes that gave rise to these very different stages of deformation. It's a wonderful miniature of many of the processes that have affected Mercury's surface, all concentrated in this very well-preserved impact structure. And then, of course, there are the huge swaths of this planet that nobody has ever seen before in this kind of detail. And with just a few seconds left, can you make a comment about what MESSENGER has revealed to us? Well, let me begin by saying it's really a sobering but exhilarating experience

to sit in front of a computer screen with colleagues that you've worked with for years, planning this mission, flying this mission for three and a half years, and to start seeing these images come down and exposing terrain that no eyes have seen before at close range. It was just a wonderful experience. That said, we're just at the beginning of sorting out what it is we're seeing. We're seeing variations in composition. We're seeing a very interesting history of emplacement processes, possibly volcanic, of deformational processes on the surface, billions of years of impact history that have given us insight into the bombardment

of the inner solar system as well as to the sequence of events that happened on Mercury. It's a treasure trove of geological information that will keep us busy for a long time sorting out how this planet works. But we finally got a nearly global data set. We'll finish that in October in terms of the first images. That will allow us to work out in considerable detail how Mercury evolved as a planet and how it compares with its sister planets in the inner solar system. So you'll finish dealing with these images pretty much just in time for that next encounter that will bring you within 200 kilometers of the planet.

I wish it were that simple. We just had a kickoff meeting this week of planning for that flyby, so we're having to multiplex here, and we're doing the science analysis in parallel with all of the planning that has to go into one of these flybys. It is the result of the efforts of many, many people who spend a lot of time making sure that everything works. And it's a credit to a very large team that the first flyby worked as well as it did.

That same team is now hard at work planning for the second flyby. And planning, I'm sure, to issue a plethora of papers that will be peppering planetary science conferences probably for years to come, I would bet. Congratulations, Sean, on an extremely successful first encounter with Mercury. Matt, thank you very much for your kind words, which I will be delighted to pass on to the team. And thank you for your interest in the mission. I imagine we'll have an opportunity to talk come October. Please, please, I look forward to it. Sean Solomon is the director of the Department of Terrestrial Magnetism

at the Carnegie Institution of Washington. He's been involved in the Magellan and Mars Global Surveyor and many other missions. He's a member of the National Academy of Sciences, past president of the American Geophysical Union. But we're talking to him today, and we talked to him a few weeks ago, because he is the principal investigator with overall responsibility for all aspects of the MESSENGER mission. Bruce is next with this week's What's Up. Emily Lochtewall is taking a break from radio duties

this week, but you can still catch her in the Planetary Society blog at planetary.org. Check it out for great coverage of MESSENGER and everything else going on in our solar system. She has an extended MESSENGER flyby article on the site as well. Time for Bruce Betts, the director of projects from the Planetary Society, to tell us what's up in the night sky. He is our personal messenger, and that is not an acronym. Why, thank you.

And I'm, well, I'm not really that speedy, but I am your messenger. You do have wings on your ankles. Well, yeah, that's true ever since, you know, the implants. But, yeah. Hey, it's total lunar eclipse time. Yeah, finally. Just going to keep talking about it because it'll be good. Let's hope for some clear weather.

Total lunar eclipse February 20th or 21st, depending on your time zone. Mid-eclipse is 726 p.m. Pacific time on February 20th. It should be visible from at least most of the event, if not all of it, from South America, most of North America, Western Europe, Africa, and Western Asia. We'll give you a link to NASA's eclipse webpage, and you can check out exactly the timing and what all parts of the eclipse you can see. And so that's going to be fun. We've also got planets in the sky for those who miss the lunar eclipse or just want something else to do when you're out bonding with the darkening moon. In the evening sky, Mars high overhead, and it's the thing high overhead that's really reddish. That's Mars. I know it's a technical thing. And we've got Saturn

also up rising in the east in the early evening. And then the pre-dawn, still quite spectacular with Venus and Jupiter, the two brightest planets, hanging out low in the east just before dawn. Jupiter is the upper right of Venus. Venus is the brighter of the objects. Good stuff. Still a busy sky. It is. You may even, coming up, be able to start catching Mercury even lower below them. And we'll check back with Mercury.

You'll let us know when there's a nearby supernova, right? Yeah. Got it on my calendar. We'll get to that. Speaking of calendar calendar this week in space history 1564 i know you you celebrate this every year don't you which one is this this is galileo galileo's born oh okay i you know i was going to say that i knew that but i know you did i was afraid it might be a supernova so yeah well now i wish i pulled out some supernovas yes there was be a supernova. Yeah, well, now I wish I had pulled out some supernovas. Yes, there was a lovely supernova in 1054.

In 1990, a little more recently, Voyager 1 took the solar system portrait that yielded the famous pale blue dot picture, but also imaged many of the other planets from high above the solar system plane. the other planets from high above the solar system plane. And in 2001, the NEAR spacecraft, the Shoemaker NEAR spacecraft, pulled off a weird feat and was an orbiter that landed successfully, landed on the asteroid Eros. Kind of bumped, right? Yeah, but successfully it was still transmitting data. Yeah.

And most important thing, by the way, was not the imaging of seeing, you know, the soil up close, but they actually, instruments like magnetometers and neutron spectrometers, things that really, the closer you get, the better and happier it is. On to random space fact! So in addition to recording the 1054 supernova that created the Crab Nebula, to recording the 1054 supernova that created the Crab Nebula, Chinese 1,000 years earlier Chinese astronomers in 28 BC, first record of observations of sunspots. Is that right?

How did they do that? I hope so. Did they, like, give their eyes to this discovery? I mean, that's science. That's great. Science! I don't know. Some kind of camera obscura doohickey thing that they came up with. Yeah, I mean, you can fairly easily project images of the sun,

so I'm guessing they did that type of thing with a pinhole. But, you know, things were kind of nasty back then all around the world, so I don't know. It was either pinholes or pinheads, man. There you go! On to trivia. We asked you in what year did Explore One, that was the United States' first satellite, launch in 1958, what year did it re-enter Earth's atmosphere? How'd we do, Matt? Huge response. I was actually surprised by this. But an enormous number of responses,

right up there with the fifth anniversary shows. I'm just going to tell you who won. It was Ron Thomerson. Ron Thomerson, another first time winner, as far as I could tell. Now, this is weird because I wrote to him because he is from Tribuco Canyon, California. And when I saw that, I wrote to him. I said, hey, Ron, my family used to camp there when I was a kid. And he said, yeah, that stuff's all parking lots now. So wouldn't you know, random.org comes up with his name. Now, you know, freaky, but that's random for you. Wow. It's almost like you're connected. Isn't it? It's a great fate of the universe. Got a t-shirt for Ron Thomerson he can wear proudly when he's out there in the canyon. We also did hear from Torsten Zimmer. A lot of people actually also told us that the batteries lasted until 1958,

but yes, it was up there until 1970. Torsten pointed out that when it came down on the Pacific Ocean in 1970, it accidentally killed a clownfish named Nemo and his friend Dory of blue tangs. That is so not true. Kids, that's not true. Really, sorry. Sorry, that's not true. Really? Sorry. Sorry, parents.

All right. On to another trivia question that who knows what disturbing answers we'll receive on this one. What famous book had Mars having two moons long before they were discovered? So in the book, talked about Mars, talked about its two moons. And this was long, long before we discovered Mars has two moons. Freaky. What is that famous book? Go to planetary.org slash radio, find out how to enter. You got

till the 18th of this month, 18th of February at 2 p.m. Pacific time to get us that answer. And win a fabulous Planetary Radio t-shirt. Thank you. You're welcome. Just thought I'd throw that in. Are we done? We're done. Good night. Alright everybody, look up the night sky. Think about how they make velvet.

Thank you, and good night. Where do you come up with this stuff? How in the world do they make velvet? Okay, well, you know, while you're looking up other stuff in the Wikipedia, like next week's answer, you can look up how they made velvet and be sure and include that in your entry. He's Bruce Betts, the director of projects. One smooth dude. He joins us Betts, the director of projects. One smooth dude.

He joins us every week here for What's Up. More from the velvety black of space next time. Planetary Radio is produced by the Planetary Society in Pasadena, California. Have a great week. Thank you.