Planetary Radio: Space Exploration, Astronomy and Science - Dwarf Planet Ceres Thrills as a Dying Visitor Closes In

Episode Date: July 4, 2018

Ceres is the queen of the asteroid belt.  Her first Earthly visitor is nearing its last days in spectacular style.  Dawn Mission Director and Chief Engineer Marc Rayman returns with stunning images taken from just 35 kilometers or 22 miles above the dwarf planet, and a preview of the spacecraft’s last days.  Planetary Society Chief Scientist Bruce Betts has a summer guide to the night sky, looks back in space exploration history and delivers another Random Space Fact.  He and Mat Kaplan also have a new space trivia question for listeners.  Learn more about all our topics this week:   http://www.planetary.org/multimedia/planetary-radio/show/2018/0704-2018-marc-rayman-dawn-ceres.htmlLearn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

A spectacular last act above the Queen of Asteroids, this week on Planetary Radio. Welcome, I'm Matt Kaplan of the Planetary Society, with more of the human adventure across our solar system and beyond. Mark Raymond is back with the latest on the Dawn spacecraft, now orbiting fantastically low over dwarf planet Ceres. It's the closing chapter in Dawn's superbly successful mission. Our ongoing mission with Bruce Betts is to bring you the best of the night sky, along with a look back through space history and a random space fact or two, that, and the

weekly space trivia contest. Bruce will join us right after we talk with Mark. Dr. Raymond is a Jet Propulsion Lab veteran who serves as Mission Director and Chief Engineer for Dawn. The spacecraft began its trek to the asteroid belt almost 11 years ago. It spent over a year exploring Vesta before firing up its ion engines for the trip to Ceres. The excitement at Ceres began even before Dawn went into orbit and has only increased as the spacecraft has revealed more and more about this not-so-tiny world that is nearly 1,000 kilometers or nearly 600 miles across.

Mark Raymond, great to get you back. Always great to get you on the show. And if you will pardon the 60s television reference, holy wonders of the solar system, Raymond. Your little ion-powered wonder has outdone itself. Well, thanks, Matt. It's always good to be on your radio show. I love it. And I'm not sure I could have said it better myself.

I'm really delighted with how well Don is doing right now orbiting dwarf planet Ceres. I told you that I sat down yesterday at the computer to write to you and say, hey, Mark, I want to get you back on to talk about this move into the slow orbit. And at that moment found this press release that took me to some of the most spectacular images that I've seen from any mission ever across the solar system. I hope that folks will go to our show page at planetary.org slash radio. And from there, I mean, we'll have some images there, but there are so many more to see, both from this lowest of all orbits and others from the one that you had already called a low orbit. I mean, if that was a low orbit, this extended mission orbit six, what the heck is this now,

XM07? Yeah, well, XM07 is incredibly low. And when we started on this second extended mission, so just as a reminder, Dawn completed its primary objectives in 2016. We had a one-year extension at Ceres, which was pretty surprising given that we had had critical hardware failures on the spacecraft that you and I have talked about on your show before, the failure of three reaction wheels. But we managed to keep the mission going, the failure of three reaction wheels. But we managed to keep the mission going, had a very productive first extended mission. And late in 2017, NASA approved us for another. And this is going to be the last. And we wanted to go out doing something spectacular. And so prior to June,

our lowest altitude above Ceres had been 240 miles circular orbit. Now, once every 27 hours, we dip down to only about 22 miles, less than one-tenth as high. And we are just getting fabulous pictures. I just think it's really cool. And I'm glad you do too. I do. And I think anybody who looks at them, certainly anybody who likes to listen to this show, is going to agree with us. Now, I referred to this, this extended mission orbit seven, and you say this is the last, right? Because we're coming to the end here. We're going to run out of gas. We are very soon.

You referred to our ion engine, the ion propulsion system. It has plenty of propellant left, but it's a different kind of gas that we're going to run out of. That is the small supply of conventional rocket propellant called hydrazine that we use to orient the spacecraft in the zero gravity of space. And we're using that up quickly because of the failure of these reaction wheels, these devices that we used to use to control the orientation. Because they're not operable anymore, we're using the hydrazine very quickly. And when it runs out in a few months, we'll no longer be able to point the solar rays at the sun to generate power. We'll no longer be able to point the antenna to earth

to communicate. We'll no longer be able to point the antenna to Earth to communicate. We'll no longer be able to point the camera and other sensors at Ceres to gather data. And we would no longer be able to point the ion engine in a direction to go anywhere. So that will be the end of the mission. And that will occur sometime between August and October. You have a pretty good idea of how much hydrazine is left, right? But there are a lot of factors involved. You can't know exactly. That's right. There are many uncertainties, and I described them in one of my recent Dawn journals. But what they amount to is we can't predict with perfection exactly when Dawn will expend its last

puff of hydrazine. And so our intent is to continue collecting this fabulous data right up until the spacecraft stops operating. We're going to get every last bit out of the mission. You mentioned Dawn Journal, and we have the latest of those that we posted at planetary.org with a link from the show pages as well on June 15th, but you had posted it even earlier on the Dawn website, part of the JPL website. And I want to thank you again for allowing us to reprint those, so to speak. I appreciate that. I know I love the blogs at the Planetary Society and everybody else does too.

And so I appreciate you're giving the Dawn journals the wider exposure. And there will be another one very soon, probably in a week or two with the latest news. And I hope people follow along with the mission because I think it's pretty exciting. I want to make it abundantly clear. You've actually already answered this, but I know that there are going to be people in the audience who are going to say, well, you still have Xenon. Why don't you just use the ion engines to keep the spacecraft oriented? Because you really can't. I mean, you need those thrusters right to point the ion engines to keep the spacecraft oriented, because you really can't. I mean, you need those thrusters right to point the ion engines in the right direction.

That's right. The ion engines are responsible for propelling the spacecraft, moving from one place to another, changing the trajectory, adjusting the orbit, that sort of thing. The hydrazine is not responsible for that, but rather is the propellant that we use to rotate the spacecraft. So they perform different functions. Now, some people may recognize that when we thrust with the ion engine, we do use them to control two of the three axes of the spacecraft. Three-dimensional objects have three axes like roll, pitch, and yaw, for example. We can control two of them with the ion engine, but we can't control all three. So once we're out of hydrazine, we're finished. Okay. All right.

But that's okay. I mean, we're way beyond what we had ever expected to get out of the mission. It's tremendous. Yeah, it sure is. Let expected to get out of the mission. It's tremendous. Yeah, it sure is. Let's talk about some of these images, including these most recent XM07 images. You know, what I did not find on very many of these incredibly close-up images is what the resolution is. I mean, clearly, we are looking at extremely high resolution. is. I mean, clearly we are looking at extremely high resolution. I mean, in general, and I guess it'll vary, how many meters are we talking about? It's just a few meters per pixel. So less than 10 meters per pixel. We don't even have a telephoto camera, what some missions would call a narrow angle camera, because Dawn was designed to map large worlds for the first time. So the design of the camera was with a wide field of view to let us cover a lot of territory. To me, that makes it that much more amazing that we're able to get these exquisitely detailed images, but that's just because we fly so low. We get down to only three times higher above the dwarf planet than you are when you fly cross-country in an airplane.

Is it difficult to get these very sharp images as you're whizzing over the surface? I mean, how fast is Dawn moving in relation to the surface of Ceres? Yeah, it's flying at more than a thousand miles per hour when it gets down to this low altitude. Yes, it is difficult. It's also difficult for us to target any specific feature because Dawn is zipping along at more than a thousand miles per hour from south to north, while Ceres itself is rotating at almost 200 miles per hour. And we have to plan this days in advance. That is, it takes several days from the time we transmit commands to the spacecraft until it actually executes them.

It turns out to be very difficult to predict with exquisite accuracy where the spacecraft will be, that is, what part of the landscape it will be over. Being off even by seconds means that terrain we expected to be in the camera field of view won't be. But we've done our best, and it is working out beautifully because some of these views are exactly what we wanted to spot. And I just think it's thrilling to be able to see this improvement in resolution. I mean, it's almost like seeing a whole new world now, even different from what we saw just a year ago. It was even as you were approaching Ceres three years ago or more, we were seeing this world really for the first time as much more than a point of light. And it was during that period that we started to see that there were wonderful mysteries there to be solved.

I'm thinking in particular, of course, of those bright spots, which we now know a lot more about. We do. in particular, of course, of those bright spots, which we now know a lot more about. We do. First of all, we can just see their shape and structure in great detail, including some of the pictures we just released yesterday. And I think people will really be impressed at the level of detail there. But we also, thanks to spectrometers, know their composition, principally sodium carbonates. So this apparently is salt, which came from underground salt water that made its way to the surface. And the cold vacuum of space at Ceres, that water froze and then sublimated, that is transformed from being a solid to a gas. So the water molecules dissipated and left behind

the dissolved salts, which reflect much more light. But when you look at these detailed pictures, you can see that that story I just told, or that description I just gave, which is very high level, doesn't have a lot of details in it. There's a lot more to be understood based on the distribution of this material, how it apparently has flowed, and other aspects of its appearance, which I think are very, very intriguing. Are there thoughts about what was or maybe still is driving this material up to the surface, the water that's there? And is there more thought that Ceres may be hiding a sort of ocean or sea as we know exists in places like Europa? Certainly the question of what is pushing this water, how did this water get to the surface?

That's an active area of investigation. It's also likely conclusion now that at one time in the past, Ceres was covered with a global liquid water ocean. It's unlikely that there's a substantial amount of liquid water underground now, but there may still be some. One of the reasons for that is that some of the materials that we found on Ceres make good antifreeze. So even if Ceres is below the freezing temperature underground, below the freezing temperature of water as we think of it, water with some of these dissolved salts may stay liquid longer. So it's an intriguing idea that there may still be liquid water below ground, probably not an ocean, but some smaller regions perhaps. We'd be too lucky to find oceans absolutely everywhere across the solar system. have the benefit of the flexing from the gravitational interactions with the planets they orbit, Jupiter and Saturn, and other nearby moons. Ceres, being pretty much on its own orbiting the Sun, doesn't have the benefit of that additional energy source. But it still has heat left over from when it formed, and that's what's providing the heat

that it has now. One of the images that we're going to put up on the show page is actually not from this lowest orbit. It's from that somewhat higher XM06 orbit. And I hope I'm pronouncing it correctly. I should remember Akator Crater, which is where the brightest of these spots is, the ones that have gotten the most attention. Right, Akator Crater, which is where the brightest of these spots is, the ones that have gotten the most attention. Right, Akator Crater. And they're called Faculae? Right, which is just the word for a dark feature on a planetary body. It has other meanings in astronomy as well, but that's how it's used here.

So a dark feature? I'm sorry, dark. I was just off by a factor of minus one. I meant to say bright. Okay. I was just scrolling through images when you were talking, and I just happened to see one was dark because I actually thought you were going to talk about a different image.

Sorry about that. But then in this lowest orbit, I mean 22 miles up, you really zoom in on more, well, at least one of these that we will also put on the show page. It's just spectacular topography. It is. It's amazing. What this tells us about the origin of these structures, the internal geological processes that created it isn't clear yet because these pictures are so new and contain so much more detail than we'd seen before. It's going to take a while to understand it. But I can't wait to see what the ultimate conclusions are from these exciting views. You've also looked over at the rim of that same crater.

That's actually what I thought you were going to refer to. So go ahead. Yeah. Well, landslides. I mean, it reminded me of some things that we've seen on the craters of Mars. Yeah. I think that is really cool. The detail showing, as you say, landslides on the crater walls, rock that protrudes from the wall, I think is really dramatic. I love these views. If you look carefully, you can see material that has slid down the slope and then stopped partway down, and you can trace its descent from the tracks that it left behind. I think these are really neat. And they also have more bright material mixed in with them in some locations. On the crater wall itself, you can see different patterns of flow, not even where there are large rocks, but just

essentially the regolith or the dirt that has flowed, I think is really, really intriguing. There's just, again, a tremendous amount of detail here. Just going through these images was so thrilling. Another one is, and here's another one I'll have to ask you if I'm pronouncing it correctly, Jueling Crater? Jueling, right. Jueling, and it's a side view, and there's some very special stuff going on under the rim of this crater. That's right. Juhling is a very interesting crater. So it's in the southern hemisphere, which means that the northern wall tends to be in the shadow because, of course, the sun is farther north than the crater.

From prior observations from Dawn, over a period of about six months in 2016, scientists recognized that the amount of ice on Jueling's north wall changed. And this is the first confirmation of a change on Ceres since dawn has been there. And the interpretation of it is that as the season progresses and the sunlight heating the floor of the crater changes, more and more water that's underground or near the ground is sublimated. That is, again, transforms into being a gas and settles on that cold northern wall. So in other words, there's basically vapor coming from the crater floor that's condensing on that cold north wall of the crater. And over the six months of the previous observations, wall of the crater. And over the six months of the previous observations, Dawn saw the area of ice grow by 470 acres. So in our previous orbit that we were in in May, we made a special attempt to observe Juling Crater again to see what the current conditions are. Those data haven't been

analyzed, but we were successful in acquiring the data. And that was a very difficult observation. We're pushing Dawn to do all sorts of things it wasn't designed to do because our goal with it, again, was just to do the first reconnaissance of these large areas of Vesta and Ceres. And now we're pushing it to get very, very detailed views. I think it's pretty exciting and there's more to come. And a lot more of these images that we could talk about, but it's a busy time for you and the mission team and I need to get you off to a meeting. But there is one more thing I want to

bring up because I know that you love these really stunning side views that look toward the horizon of Ceres. Yeah. And we did get some of those again in our previous orbit in May. So three times, we turned the spacecraft at the expense of spending a little extra hydrazine, but I felt it would be worth it because I think these views are so appealing. I think they really pull you in and show you a different perspective on an alien world. And it's one that you could imagine if you were lucky enough to be there in your own spaceship, you might see out the porthole or one of the other windows when you're in orbit. They have scientific value as well, but my motivation in

getting these images was principally that I thought they would be very appealing. And I think they are. Of course, at the time, I didn't know we were going to get these even more spectacular images from lower altitude. But fortunately, it's not a competition because now we have them all. Mark, what close-up science is still ahead of us in the month or two left to dawn? Every 27 hours, we continue to get new pictures. Progressively farther south, Akator Crater is at around 20 degrees north latitude. The orbit is gradually shifting south, and so we're seeing new terrain on each orbit. on each orbit. We're also measuring nuclear spectra, which will tell us about the elemental composition of Ceres. That is, if you remember back to your periodic table of the elements, which atoms on that periodic table and in what proportions are present on Ceres. And we take visible spectra and infrared spectra to determine the minerals that are there.

And we measure the gravity in hopes of determining something about the subsurface structure of Ceres that is right underground at the locations that Dawn is flying over. So there's a lot more data still to be gathered. And again, we're going to do it until the very last moment. And thank goodness for that. to do it until the very last moment. And thank goodness for that. It's all thrilling. I look forward very much to talking to you again, could be after the end of this spectacularly successful mission, Dawn at Vesta and now Ceres. Mark, it's always a great pleasure. Thank you so much. Thank you, Matt. I really appreciate your interest. And I'm grateful for the opportunity to talk about this with you and share it with all your listeners.

Mark Raymond, Chief Engineer and Mission Director for the Dawn Mission, now closing out its spectacular time at Dwarf Planet Series. Time for What's Up on Planetary Radio. We are in the Planetary Society headquarters studio with the chief scientist for the society, Dr. Bruce Betts. Welcome. Thanks, Matt. Good to have you here. We just had to shush everybody outside because the door, we have a nice studio, but the door really sucks. Yeah, we're going to redo that. And you had a great idea with the light. I want a big flashing red light like a real radio studio, like the 1940s, you know, on the air.

Welcome to another episode of Planetary Radio. Got to put your hand over your ear. Oh, sorry. Yeah, people can tell the difference now. Welcome to the... Stop it. So how do you, like, know what's up in the sky? I would love to, thank you. And I know it's getting better and better.

What do you think I'm going to talk about, man? Mystery. No, Mars. Mars, Mars, Mars. Mars, Mars, Mars. Mars is approaching opposition, opposite side of the Earth from the sun. On July 27th, it'll have the closest approach to Earth it has had in 15 years on July 31st. And it is already basically as bright as Jupiter coming up a little after sunset in the early evening. But there are also three other planets.

You can go all the way across the sky almost. And you've got Venus in the west. And then moving across the sky, you've got bright Jupiter and then yellowish Saturn. And then Mars coming up, and it'll be rising earlier and earlier. And it's all groovy. Oh, one other note. July 9th, Venus will be very near the brightest star in Leo, Regulus, and so you can watch it kind of moving towards it

and then past it in the evening sky. Is Vesta still visible to the naked eye? Maybe. It's dimming. If you're in a really dark site and know where you're looking, then you should still be able to pick up Vesta, but it's already getting trickier. But with a finder chart and some binoculars or telescope, you should be able to see it, the brightest asteroid out there in the asteroid belt. All right, we move on to this week in space history. It was a big week. July 4th alone was a party. I mean, you had Pathfinder

landing in 1997, Deep Impact slamming into a comet on purpose in 2005, and 2016, Juno went into orbit around Jupiter. Also this week, 2003, Opportunity launched. We had a big party for Deep Impact. We did. Comet Bash 2005. It was fun watching the big plume coming out from it. 13 years ago.

I don't want to even think that. It's less than half a Saturn year. I feel much better. Good. I'm glad you do. Speaking not at all about Saturn, we move on to Random Space Fact. Astronom Space Fact. This is the NBC Broadcasting Network. No, it's really not. Not at all. We wish.

So back to asteroids. And remember, there's a lot of – there's new great content on our website about asteroids and the asteroid threat. We've got a frequently asteroid questions from me and five-step plan to prevent asteroid impact update on our shoemaker neo winners videos and of course our kickstarter raising money and selling cool products planetary dot org planetary dot org check it out that was all by way of saying related to asteroids hitting the earth about 30 small asteroids a few meters in size hit Earth every year as detected by the U.S. Department of Defense assets. Optically or seismically, how do they do that? Is it secret? I could tell you, but you'd have to. Yeah. So actually, no, they didn't share with me. No, it's a nice side benefit of looking for other hot things that are happening with high energy is you actually get data on these bright fireballs that happen in the sky, some of which rain meteorites onto the ground, but don't do any significant damage.

But it's out there. And we move on to the trivia contest. And I asked you, what is the approximate altitude range above the surface of the Earth of the International Space Station? And I said approximate. And I failed to give a time frame, so we may get different answers. But they're still going to be in the same general ballpark. We did get lots of different answers. You said approximate, and it is within, in fact, the current time frame. Mark Graham in Perth, Ontario, Canada, was chosen by random.org to have his answer evaluated.

He said approximately 400 kilometers or 240 miles. That is correct, and they've been sticking closer to that altitude in recent years. They were lower a few years ago and then going up and down from about 330 kilometers up to 410, but they're staying closer to that 400 kilometer mark altitude. Congratulations, Mark. I thought we were done with this. I thought we'd used them all up, but you get the last signed hardcover copy of Chasing New Horizons Inside the Epic First Mission to Pluto by Alan Stern and David Grinspoon, and a 200-point itelescope.net astronomy account. We'll come back to that. A lot of people said that this was an easy one for them to figure out because it was pretty easy to look up.

But, of course, we got people who went above and beyond even though we told them it wouldn't help them win because we did say if you want to give us some of those unique, extraordinary units. Oh, excellent. I always enjoy that. We had a bunch here, so I'm going to go through them quickly. And I'm sorry I can't get to everybody's here. Brian Mangold, Maricopa, Arizona. Oh, here's the random space fact that I told you that somebody submitted.

It came from Brian. He said, if you had a basketball representing the Earth, the ISS would only be seven millimeters above the surface of that basketball. Pretty good RSF. It is a good RSF. People lose track of how little into space it is compared to the Earth. We've talked about that before, and we'll talk about it again, because get it in your head. Alex Hayden also got the correct numbers and then gave it to us in light years, specifically 400 billionths of a light year. Well, that is a practical unit. Steve Wynnell, about 5,500 ISSs, about 5,500 International Space Stations stacked one on top of the other. That's a self-referential unit. Nice use of self-referential. I'm always looking for opportunities.

This one's interesting. From Joe Murray in Hoboken, New Jersey, he says roughly a tenth of Juno's altitude above Jupiter, which is about 26, 2700 miles. And that's obviously at the closest past to Jupiter because it swings way out there, right? It does. They're in a quite elliptical orbit. Martin Hajoski, a regular with us from Houston, Texas, a fan of Middle Earth. He says says that would be 68 to 90 lar or 340 to 450,000 ranga for a true orbital ring of power. That's just beautiful. Here's one of my favorites. Robert Johannesson from Norway, Bergen, Norway. He wanted to put it in units that his son would like.

He wanted to put it in units that his son would like, somewhere between 3.3 and 4.1 times 10 to the sixth popsicle sticks. Let's build that. Dave Fairchild, our poet laureate, it wasn't enough for him to give us a poem this time. He did that too. He said about 3,600 Saturn Vs, which in today's dollars would be about $5.4 trillion to build. Sounds about right for a space ladder or elevator. Yeah, I'm guessing it would cost even more once you tried to figure out how to bolt them all together. All right, so here's his poem, which I think you'll also like.

The ISS circles above us each day and roughly in orbit of 400 Ks, which is more or less, as this poet deduces, 104,900 bruises. Well, there's an image. Finally, from Daniel Kazard in the UK, who always sends us wonderful images to go with these. in the UK who always sends us wonderful images to go with these. He says, based on not the average nose, but what he estimates astronaut Mike Massimino's nose to be, about 8 centimeters. The average is about 5.8. So mine must be up there with Mike's. He says it would be about 324 million mass noses to the ISS.

Well, that does put it in perspective. You wouldn't want to have hay fever then. All right. We'll have to get this one to Massimino. That's it. Thank you, everybody. That was great fun. And we are ready for another contest.

What did Yuri Gagarin eat in space? What did he have for lunch? Anyway, what did he eat in space? Go to planetary.org slash radio contest. Hmm, probably wasn't Tang. You have until Wednesday, July 11 at 8 a.m. Pacific time to get us this answer and win yourself a Planetary Radio T-shirt and a 200-point itelescope.net account. The T-shirt you can see at chopshopstore.com. Go right to the Planetary Society store. All our swag is there. The 200-point itelescope.net account from that worldwide network of telescopes,

it's worth a couple hundred bucks U.S., so they tell us. All right, everybody, go out there, look up at the night sky, and think about if you were to put a condiment on an asteroid, what condiment would it be? Thank you, and good night. Are olives condiments? Because it looks like Ryugu is covered with olives.

Oh, I thought they were cornflakes. Planetary Radio is produced by the Planetary Society in Pasadena, California and is made possible by its ion-powered members. Mary Liz Bender is our associate producer. Josh Doyle composed our theme, which was arranged and performed by Peter Schlosser. I'm Matt Kaplan, Ad Astra.