Planetary Radio: Space Exploration, Astronomy and Science - A MESSENGER From Mercury—Principal Investigator Sean Solomon Returns

Episode Date: October 28, 2014

MESSENGER has been orbiting the innermost planet for more than three-and-half-years. Principal Investigator Sean Solomon returns with a status report as the mission enters its final phase.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

A Messenger from Mercury, this week on Planetary Radio. Welcome to the travel show that takes you to the final frontier. I'm Matt Kaplan of the Planetary Society. We are in the final months of a mission that has revealed many of the secrets and many new mysteries about our solar system's innermost world. Messenger Principal Investigator Sean Solomon is back with an update. Bill Nye is watching as bold new technologies make reaching space easier and cheaper. And we'll look to Mars for the answer to this week's What's Up Space Trivia contest with Bruce Betts. The Geological Society of America just completed its annual meeting.

Senior editor Emily Lakdawalla was there. Emily, welcome back from Vancouver, where you attended this geology conference. Tell us just a little bit about it, an overview. Well, like any other scientific conference, it's a bunch of scientists getting together to talk about their work. You can always tell what kind of conference you're at by the dress code that people seem to follow. This one, most people were wearing hiking boots and technical jackets. I felt a little out of place. But yeah, it's a geology conference, mostly field geologists, and Curiosity is a mission that's really doing field geology on Mars. So the session fit right in. So you have written this really interesting

piece. It's a long one. It's a little mini geology textbook about what appears to be a mystery, maybe even close to a paradox on the red planet. I think that if you call it a paradox, it demonstrates that we don't actually understand what's going on. So the mystery is that if you look at the rocks that Curiosity has been examining, you'll find they're all sedimentary, which is a type of rock that is composed of broken pieces of other rocks that have been cemented together. And that they are not igneous, which is another of the major classifications of rocks, which is rocks that solidified from a melt. But the weird thing is that all of the rocks that Curiosity is looking at, they dominantly have a composition of an igneous rock called basalt. And basalt is a kind of rock that doesn't play very nicely with water. So the fact that you have this basaltic composition everywhere that you look, and yet they're all sedimentary rocks, which mostly need water to form, is a real puzzle. And it's

definitely telling us something important about the geologic history that made the landscape that Curiosity is exploring. We know there were habitable environments there there are some rocks that contain clays which do show signs of having interacted with water but they're few and far between which which may tell us that water's activity was not as active on mars as it was on earth or it may just be that mars is not like Earth. It's a different planet. And we're just not understanding properly what the chemistry is telling us. And frankly, I'm leaning toward the latter. I think that there's a lot that we still don't understand and that we just need to keep reading the rocks until we understand it.

Which is pretty exciting in itself. It's an October 24th entry in Emily's blog at planetary.org. October 24th entry in Emily's blog at planetary.org. Say something as well, though, about these amazing images that are coming from these instruments that get up close and personal with that dirt on Mars. That's right. One of the main instruments that I was talking about in this blog entry is MOLLE, which is the Mars Hand Lens Imager. It's a color camera that's on the end of the robotic arm. And it really has to be one of my favorite instruments on this mission because it's so versatile. It can get super close to rocks. It can see grains as fine as the finest sand, helps us tell apart the different kinds of sedimentary rocks. But the arm can also be used to take self-portraits and wide-angle views of the landscape.

It really is a tremendous workhorse of an instrument. It's been really fun to play with the images. tremendous workhorse of an instrument. It's been really fun to play with the images. Beautiful views from Curiosity waiting for you at planetary.org, where Emily, our senior editor and planetary evangelist, writes all the time in her blog. She's also a contributing editor to Sky and Telescope magazine. Thanks, Emily. Thank you, Matt. Up next, Bill Nye, the CEO of the Planetary Society. Bill, it's all about making it cheaper to get up to low-earth orbit, right? Yes. So SpaceX, Space Exploration Technologies is planning to land, re-enter a rocket and land it

on a floating platform. Wow. And the significance of this is then you wouldn't need to have rocket launchers on land. You could go to anywhere to the best place on Earth for your particular mission to get your particular orbit at your particular inclination to the equator and land there. And this could lower the cost of everything, not just the equator, but anywhere you'd want to go. Isn't it also just a big part of this that they're going to try and land on this? That's right. Yeah. Re-enter and land on, you know, It reminds me in every way of people who land fighter planes on aircraft carriers. I mean, there's a lot of motion when you're landing on a ship, let alone the small landing pad. It's quite a thing. So a reusable first stage, getting closer from SpaceX. At the same time, there are at least a couple of companies that are building rocket engines in a novel new way. In additive manufacturing, printing rocket engines. You can go to office supply stores and get a 3D printer for like $1,000 US.

Yeah. Unbelievable. So if you make these machines enormous and you find ways to replace plastic with metal, they are apparently manufacturing the bell, the nozzle, the outlet of rocket engines, making them one at a time in these very, very large, what you would call printer machines. So by making rocket engines in this way, if it works out, it will lower the cost of rocket engines. And this will lower the cost of low Earth orbit and we've got to figure, make missions to deeper, farther places in space faster, better and cheaper.

It's exciting. Thank you, Bill. Thank you, Matt. He is the CEO of the Planetary Society. Up next, the principal investigator for the MESSENGER mission which will be coming to an end at Mercury in just a few months. MESSENGER MESSENGER is the Mercury Surface Space Environment Geochemistry and Ranging Spacecraft. MESSENGER has been orbiting First Rock for three and a half years,

returning images and data that may keep scientists busy for many, many years to come. Sean Solomon has served as principal investigator from the start. He returns to Planetary Radio as the mission enters its final months. Sean directs Columbia University's Lamont-Doherty Earth Observatory. He's had a part in many other missions, including Magellan at Venus, Mars Global Surveyor, and the recent GRAIL Lunar Orbiter. During his nearly 20-year tenure at the Carnegie Institution, he served as that organization's principal investigator for work with NASA's Astrobiology Institute. What follows are merely excerpts from my three-times-longer

conversation with Sean. You can hear everything he had to say on this week's show page at planetary.org slash radio. Sean, welcome back to Planetary Radio and congratulations on learning that you are going to receive the National Medal of Science. That's very, very impressive. Thank you, Matt. It's a wonderful honor, and I'm humbled by the fact that so many very distinguished scientists are never tapped for that award, so it's particularly special. As you wait for that event, there is a spacecraft that continues to circle Mercury. It was only just over a couple of months ago that you celebrated your 10th anniversary in space.

Congratulations on that as well. Thank you again, Matt. The business of exploring the planets is not for the impatient. Many of the trajectories that take us to the, even to close neighbors in the solar system, involve a substantial investment of flight time. But it worked exactly as planned, and since then, the statistics are just amazing.

Over 3,500 orbits, more than a quarter of a million images, more than 10 terabytes in total of publicly available science data. I went on the Messenger website this morning, and I counted just in the last five years, just since 2009, counted just in the last five years, just since 2009, nearly 200 peer-reviewed papers based on what Messenger has sent back to us. That is quite an accomplishment. Well, thank you once again. It's always an opportunity for discovery to go someplace and do a thorough examination of a planet for the first time. The most recent significant science result, I suppose, are these images, spectacular images, taken at the North Pole of Mercury and taken of some material

there that I guess had already been more or less confirmed, but it's truly amazing to see water and what else is up there at the North Pole. Well, the idea that water ice is trapped in permanently shadowed regions at the poles of Mercury goes back more than two decades. MESSENGER took a host of instruments that were designed to pursue that hypothesis further. Of course, we were able to document areas of permanent shadow much more rigorously with imaging over a complete Mercury solar day. We carried a neutron spectrometer that's very sensitive to the presence of hydrogen, enhanced

amounts of hydrogen on the surface of the planet. We had a laser altimeter that served as an active device to measure the reflectance of the surface. And because we measured the topography with the laser altimeter, we were able to make very detailed maps of the surface temperature of Mercury over the course of a solar day and the near-surface temperature and map those areas where water ice would be stable. And all of those measurements, the hydrogen measurements inferred from the neutron spectrometry,

the thermal models derived from the measured topography, and the reflectance of the surface at the wavelength of the laser all confirmed the idea that went back more than 20 years that water ice is present. But what the laser showed us was that the surface reflectance was not, for most of the deposits, as bright as would be expected if the water ice were present all the way to the surface reflectance was not, for most of the deposits, as bright as would be expected if the water ice were present all the way to the surface. The idea that had first been put forward by David Page's group at UCLA, that we should find on the surface of Mercury not only water ice, but other volatiles delivered by comets and volatile rich asteroids. And the leading candidate for this really dark material was this complex organic carbon-based material that coats many of the surfaces of small solid objects in the outer solar system that is seen in the spectra of comets

and that is seen as well as a complex organic macromolecule in organic-rich meteorites. That was really a surprise, that Mercury is a witness plate not only for the delivery of water, presumably from the outer reaches of the solar system into the orbit of the innermost planet, but also the delivery of other volatiles, including carbon-rich compounds. We're left with an interesting result that the planet closest to the sun and the planet with the biggest extreme in temperature, 600 degrees between day and night at the equator, might have some of the best record of how volatiles have been delivered to all of the inner solar system, including the polar regions of Mercury. And perhaps, therefore, a window also on the earliest days of our solar system?

I think that's a fair statement. The deposits that we're looking at in the north polar region of Mercury don't go back to the earliest days of the solar system. They're too pristine. back to the earliest days of the solar system. They're too pristine. The water ice is too clean. The brightness is too different from that of the average of Mercury. So there couldn't have been much lateral mixing, as you would expect by impact gardening over hundreds of millions or billions of years. But I think we're seeing the process. I think we're seeing the fact that comets and volatile rich asteroids over the history of the solar system are sent inward to the inner reaches of that system or even to the sun often enough that there are collections of recent deposits, the tail end of what must have been a long and complicated history of delivery of material from the outer solar system to the inner planets. That's the last chapter of a very interesting book, the early chapters of which on the Earth must have figured in some way into the prebiotic

chemistry that led to the origin of life. Was it a particular challenge, even with this very sophisticated spacecraft, to get those detailed images at the pole? It was. It was. We're imaging areas that are in permanent shadow. And so the question is, what are we seeing? What is the source of the illumination? We did something with the messenger images that had already been done at the moon, where there are areas in permanent shadow at the lunar poles. And that is to take advantage of the digital technology of modern imaging, to use the broadest spectral band on the filters on our imaging system to take the longest exposures, to have the field

of view as confined as we could to the permanently shadowed regions, and then simply expose the images long enough that barest amounts of scattered lights off the sides of the craters that had these permanently shadowed floors would be enough. It seems to be a very recent chapter in Mercury's history, and therefore a fascinating look into the movement of volatile materials across the solar system on geologically short timescales. Sean Solomon of the Messenger Mission, Exploring Mercury. More is just a minute away here on Planetary Radio.

Hi, this is Casey Dreyer, Director of Advocacy at the Planetary Society. We're busy building something new, something unprecedented, a real grassroots constituency for space. We want to empower and engage the public like never before. If you're interested, you can go to planetary.org slash SOS to learn how you can become a space advocate. That's planetary.org slash SOS. Save our science. Thank you.

Random Space Fact! Nothing new about that for you, Planetary Radio fans, right? Thank you. Would you, Woody? I really wouldn't. A new random space fact video is released each Friday at youtube.com slash planetary society. You can subscribe to join our growing community and you'll never miss a fact. Can I go back to my radio now? Welcome back to Planetary Radio. I'm Matt Kaplan. Sean Solomon is principal investigator for MESSENGER, the orbiter that has revealed the planet Mercury as never before. Sean told us the story behind the imaging of water ice at Mercury's North Pole, water ice that is apparently coated by a dark layer of complex organic material probably deposited over the eons by passing comets.

It's just one of scores of major accomplishments and discoveries made by the spacecraft, beginning even before it began circling Mercury more than three and a half years ago. Again, my entire more than half-hour conversation with Sean is available at planetary.org slash radio. Another major goal of the mission was to measure the composition of the surface material on Mercury. We set out to do so in the expectation that we could distinguish among the theories that had been put forward to account for the fact that the material that makes up Mercury is much denser than that of the other terrestrial planets. The most straightforward explanation of that high density is that Mercury is more rich in iron, the most common heavy element in the sun and in meteorites.

And so the ratio of iron metal, presumably in Mercury's core, to rock is about four times higher on Mercury than it is for Earth or Venus or Mars. Mercury is really the iron planet with a comparatively thin shell of rocky material, and that's been known for half a century. But we had several competing ideas for why that should be so, ranging from processes very early in the condensation of solid material out of the hot gas and dust that surrounded the early sun in the nebular disk to processes late in planetary accretion that involved removal of a large fraction of Mercury's outer silicate shell,

either by a very hot solar nebula or by the collision of a differentiated planet with an object nearly the same size. What we did not expect was that we would make measurements of the composition that would reject all the theories. We did that because Mercury, the planet closest to the sun, supposedly born by violent energetic processes that gave rise to the high metal fraction, a giant impact, bathing the planet in extraordinarily hot solar nebula, or confining the building blocks of Mercury to those materials that are solid only at the very highest temperatures. All of the ideas for how Mercury was assembled predicted that Mercury, like the Earth's moon,

should be deficient in volatile elements, the elements that are easily removed at high temperatures. And when we actually made the measurements of sulfur, of potassium, of sodium, of chlorine, all of which are volatile elements, the abundances were not deficient. The abundances were high. They were as high or higher than at the surfaces of the other terrestrial planets. They were as high or higher than at the surfaces of the other terrestrial planets. So none of the ideas that have been in the literature for decades as to how to make an iron-rich planet among the other rocky planets matches what we see. It does seem to be proof once again that exploring the solar system delivers an unending series of surprises. That is true. Every place we visited

has been different from what we expected. But there's another lesson beyond that, and that is that one must be prepared for surprises. All good things come to an end. After two extensions of its primary mission, Messenger's finale will come in the spring of 2015 after the supply of fuel that has allowed it to maintain orbit runs out. Before that closing act, Sean Solomon's team will be keeping the spacecraft very busy, dipping at times to just 25 kilometers above the surface of Mercury. It's just possible that MESSENGER will help us continue to explore after it has smashed into the surface of the planet. We'll be tracking data as long as we can listen to the transmitter.

We'll probably be gathering the last few bits of data even minutes after the crash because, of course, the radio waves take some time to get from the spacecraft to Earth. Incidentally, one of the interesting aspects of crashing under Mercury is that we will expose fresh material, material that has not been exposed to the processes at the surface that space weathered the soil, that darken it, that redden it. Big question for Mercury has been how to interpret the color and the darkness of the surface in terms of those space weathering processes. Well, we have an opportunity to monitor a small, very small impact

that is not only fresh, but whose timing is precisely known. So we're making predictions as to where the impact on Mercury will be by the MESSENGER spacecraft. And we're conducting an imaging campaign at the highest resolution we can achieve of the region around the expected impact point. And we want to hand those images to the next spacecraft mission that will visit Mercury a few years from now and say, please look in this area because whatever change you see was the result of the crash of our spacecraft.

Please not only look for the site of where we crashed, but see if you can learn something about the exposure of fresh material on the surface of the innermost planet. So even with its death, MESSENGER will be having a deep impact, if you will, on science that we gain here on Earth. You have been extremely generous with your time, Sean, and I don't want to take up any more of it. I certainly hope, though, we can talk to you again as this mission wraps up. The only other thing that I want to mention to you

is something that I discussed briefly with Emily Lakdawalla on this program a couple of weeks ago, and that was a picture that Emily posted, actually a video, an animation, that she posted as part of her blog at planetary.org. It may not have been scientifically significant, but it was certainly charming to see a lunar eclipse from basically another planet in our solar system. Indeed, this eclipse was in early October,

and the imaging team put together this wonderful time-lapse animation. First you see the moon, and then as the eclipse progresses, it almost blinks out of view. It was a wonderful perspective on the many ways of viewing our solar system and our own binary planet system, the Earth and the moon. I think Newton, Galileo, Kepler, I think they all would have been quite proud. They would have been. We might have gotten in trouble with the more dogmatic figures of Galileo's era. You might still be in trouble with a few people with that kind of science. But fortunately, they are in the minority.

And the majority of us, and certainly listeners to this show, Sean, we are very happy to have the opportunity to talk with you once again and look forward to the next opportunity. It's always a pleasure talking to you, Matt, and I look forward to that as well. Sean Solomon is the principal investigator for MESSENGER, the Mercury Surface Space Environment Geochemistry and Ranging Mission, managed by the Johns Hopkins Applied Physics Lab. He directs Columbia University's Lamont-Doherty Earth Observatory, and we've been talking to him from his office at Columbia. Up next, our friendly local astronomer Bruce Betts will take us through what'sts in the studio here at the Planetary Society, this is where you have made some of your random space fact videos, right? It's where some of the magic happened.

Which are now up. They're on the site. You can look at them at the Planetary Society YouTube channel, and they truly are great. Thank you. You're welcome. We had fun making them. Merk Boyan, our video guru who came on board recently, and so check it out. I dutifully will post them at my Twitter feed, Random Space Fact, as well. But they live at the Planetary Society YouTube channel. All right, what's up? We've got, in the evening sky, you can still check out Mars, looking reddish over there in the southwest.

Saturn maybe, but it's awfully tough really low down in the southwest. Speaking of tough, in the pre-dawn, we have one of those brief Mercury apparitions. So if you've got a very clear view to the east, you can see Mercury in the pre-dawn. You can easily see Jupiter up high in the east, east-southeast, and looking quite bright. We move on to this week in space history. It was 1991 that Galileo spacecraft flew by Gaspra asteroid flyby,

particularly significant because it was the first ever spacecraft flyby of an asteroid as it was headed out to eventually get to jupiter on to oh that was that was nice very melodic i like you thank you very much this is from emily emily uh in researching curiosity uh threw this out to me as a random space fact. The Curiosity rover has 57 meters of aluminum and steel tubing as part of a cooling and heating system that takes heat from the radioisotope thermoelectric generator and puts it either inside the rover or out to the atmosphere. They have a lot of waste heat to get rid of in addition to the power produced.

57 meters. That's a lot. By the way, how's the Tony Bennett duo album coming along? Oh, we're doing great. I keep saying, Tony, sing a little more like me. Okay, it actually broke down. I'm sorry to hear that. Thank you.

So anyway, we move on to the trivia contest quickly and with abandon. We asked you, what is the last full year in which there were fewer than five working spacecraft at Mars, including orbiters, landers, and rovers? How did we do, Matt? You scared most people off with this one. Roar. We do, Matt. You scared most people off with this one. Those who did respond, I know there was a little bit of controversy, just as we were considering these winners. Because you had something else in mind. The question was the last full year. You meant to say calendar year, didn't you?

I did, but I think I'm even off on that. I don't know what was going on in my head. What I really was thinking was when's the last time we had fewer than four? But I didn't ask that. So that's not what we're addressing, although it would be nice if people just read my mind. So 2011 was the last year because it was this window between spirit

apparently giving up the ghost, the Martian ghost, and curiosity arriving at Mars. Most of the people who did enter this week, including Carl Anderson, said, yes, 2011, there were four operational missions working at Mars. And we're going to accept that? That is correct. All right. We only heard from a couple of people, John Gallant was one of them,

that those four were Mars Reconnaissance Orbiter, Mars Express, Mars Odyssey, and Opportunity. It is Carl Anderson who is our winner this week and is going to get that Chop Shop Beyond Earth letterpress poster, the Beyond Earth one that has lots and lots of robotic missions on it. It's a terrific poster. That comes from our friend Thomas Romer at Chop Shop. By the way, did you know that there is a Martian calendar as well? Somebody gave us the year in. The year.

I'm certainly familiar with scientists referring to the subsolar longitude L-sub-S to identify the season. But no, I guess I'm not. Now, here you have it. It came from Stephen Porter in Piedmont, California. Stephen Porter in Piedmont, California. Crazy enough, someone made a Martian calendar, and it's the Darien calendar, which says that this 2011 time period fell within the years 213 and 214 of the telescopic epoch. And then he finishes with, huh? Epic.

I think that's your line, actually. Huh? Just like I thought. All right, we're going to go Night Sky Constellations. What constellation winds its way between Ursa Major and Ursa Minor, or the Big and Little Dippers? What constellation does that? Go to planetary.org slash radio contest. Get those entries to us by Tuesday, November 4th at 8 a.m. Pacific time.

And we are done. All right, everybody go out there, look up at the night sky, and think about one of Matt's favorite things, acoustic absorbing materials. Which is what made this room so great. No echo, no echo, no echo. He's Bruce Betts, the Director of Science and Technology for the Planetary Society, now featured in the Random Space Fact video series on your local device.

And he joins us every week here for What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by the fleet of foot members of the Society. Clear skies. Music Music Music Music