 that's a nice time to try that. We can get all of your input on what's worked best for you for virtual presentations and star parties and we have the virtual site set up on the Night's Night Network website so I'll put a link to that but I know you all have more experience than we do with this so. You know Amy Oliver is on the roster who did the breast practices webinar for us earlier this year and she's on the roster for the ASPs meeting this December to follow up on that topic I believe. And she's just south from you Carl. Do you know Amy? She's down at what Whipple Observatory right? You know Smithsonian. I'm not sure if I know her and I've spent I used to spend a lot of time at the Mount Hopkins here at Whipple but I haven't been there in about 10 years now. Okay. All right so we're almost there. I know. So another reminder before we start going to for everyone in the chat please make sure that you go down there and change your setting so it says two panelists and attendees. That includes the panelists because often we'll sometimes forget that's true for us as well. Very easy to forget. I just changed mine and I always mix it up. So with my presentation in presenter mode I don't think I can see the chat at all so if you know a good question comes up like you said just break in and let me know. Okay. Oh yeah. All right well let me go ahead and start. So we are at the top of the hour and so welcome hello everyone and welcome to the November NASA night sky network member webinar. We're hosting tonight's webinar from the Astronomical Society of the Pacific in San Francisco California and from upstate New York and we have our guest speaker Carl Hergen-Rother. Did I see that right? I hope. Hergen-Rother close enough. Okay from the University of Arizona's Lunar and Planetary Laboratory and so welcome to everyone joining us both on Zoom and the YouTube livestream. We're very happy to have all of you with us. These webinars are monthly events for members of the NASA night sky network and we're glad that other people who aren't necessarily in the night sky network can join us on YouTube. For more information about the NASA night sky network there should be a link somewhere on the YouTube page for this video as well as the Astronomical Society of the Pacific so check those links. Well before we get started with Carl here's Dave Prosper with just a few announcements. Alrighty. Hi folks. So I just have a couple of items here. Just to make sure. Okay for one we have, oh I'm just switching to views here. Okay. We have just a little bit of news. Mostly follow-ups from the last couple of announcements. We have news about the PINs. They should be arriving sometime in mid-December and we're going to have information about that later on this week just for folks who are wanting to order requirements and so on and we know that outreach along with a lot of other things this year has been a bit of a challenge and we do want to recognize everyone's efforts big and small online and in person so that's why we'll have some updated and looser requirements and so that'll be in your inboxes by the end of this week if all goes well along with notice of the latest night sky notes if you're subscribed to that newsletter. I try to have them out by the 15th of the month when all goes well but I made the mistake of taking some time off at the beginning of the month. It's messed up my schedule a bit. The article is almost done and we'll hopefully have that out to you in the next couple of days too at least by the 20th which is our kind of our kind of our cutoff date for that. But probably the most exciting news for some folks is that we actually have more planet stickers created by Geraldine Ramirez. People love the stickers and we let Geraldine know and she has flushed out the rest of the solar system and you can find those at bit.ly slash I saw planets or at the link I just put in the chat here and that's all I have that's for our program news back to you Brian. All right thanks Dave so for those of you on zoom you can find the chat window and the Q&A window at the bottom edge of the zoom window on your desktop please feel free to greet each other in the chat window making sure that you select a panel of two panelists and attendees at the bottom. If you have any technical difficulties you can send us an email at night sky info at astrosociety.org. If you have a question for Carl this evening that you would like him to answer please type it into the Q&A window not the chat window please put it in the Q&A window that helps us keep track of it and we don't lose it amongst all the greetings of you know possibly hundreds of chat messages that we have there. So again I'd like to welcome everyone to the November webinar of the NASA night sky network this month we welcome Carl Hergenrother to our webinar. Carl is an observational astronomer at the University of Arizona's lunar and planetary laboratory specializing in the study of comets and asteroids. He's a member of the science team for the NASA OSIRIS-REx mission. With OSIRIS-REx he's responsible for leading the effort to select and remotely characterize Bennu monitoring the near Bennu space for ejective particles and helping to coordinate the target asteroid citizen science project and it's possible that some of you have participated in that and if you happen to have done the target asteroid citizen science program put a little jot something into the chat and let us know if you've participated in that I think that Carl would love to hear from any of you that may be involved with that. Carl is also an avid backyard observer where his go-to equipment are a pair of 30 by 125 binoculars he enjoys visually observing comets meteor showers and galactic nobby and is also the comet section coordinator and associate director of the Association of Lunar and Planetary Observers or ALCO. Please welcome Carl. Thanks for having me so hopefully soon we will see my title page. There we go. There we go it looks great. Okay great so yeah thanks for having me from you you know clear dark and still warm Tucson. I believe this is actually the second Osiris-REx talk that has been presented to the night sky network. Ed Beishor who was at the time our deputy principal investigator talked to everyone about a few weeks right before our launch back in 2016. So what exactly is Osiris-REx? Well it's a NASA funded spacecraft mission and in fact it's a new frontiers class mission to go to a nearby near earth asteroid called Bennu characterize it collect the sample from its surface and bring that sample back to earth for study and analysis in 2023. Like a lot of missions nowadays its name is an acronym the days of Voyager 1 and 2 are kind of gone this I think would have been new frontiers 3 if we had gone with the old naming but Osiris-REx itself is an acronym and the acronym kind of spells out the main science investigations that we were primarily interested in. The reason why we went to Bennu is because it's a carbonaceous asteroid. Carbonaceous asteroids are usually carbon rich can oftentimes be have water and the reason why really interesting is that they haven't changed much over history to solar system unlike a lot of other bodies like the earth or even s-type asteroids that had a lot of radioactive metals when they formed so you had a lot of isotopic decay carbonaceous asteroids didn't experience that so they never melted they never heated up they didn't differentiate like the earth does where you got the heavy stuff in the core lighter stuff floating on the surface. So going to an asteroid like Bennu is like going kind of back in time to the formation of the planets and the early solar system there's also a belief that asteroids like Bennu these carbonaceous asteroids delivered much of the water as well as possibly even the organics that we ourselves are made of to earth so that's where the origins comes in. The next part of the name is spectral interpretation the SI there's a million or so asteroids that we know about there's hundreds of thousands of meteorites and they don't quite look the same we know that meteorites are coming from the asteroids but there's a disconnect there so hopefully by going to an asteroid that we've intensively studied from the ground and now we've studied and characterized from orbit and now bringing samples back we can better interpret what our ground-based telescopes are saying about the other million or so asteroids. RI resource identification humanity is already a space faring species and at some point we're going to be an interplanetary species and when we do that we're going to have to learn how to live out there among the other planets the comets and the asteroids and the asteroids especially the earth asteroids are going to probably end up being the gas stations of the future where you can drop off and get your building supplies you can collect hydrogen you can collect carbon you can collect water and water is great for a lot of things not only is it great for drinking it also can be used as a fuel and of course you need it for growing plants and such. Security we know asteroids are dangerous we know asteroids hit the earth every day they're usually small so you only see them as meteors but we know in the past asteroids have caused some bad times here on earth and one of these days that may happen again. As it turns out the asteroid Bennu though we did not know this when we selected the asteroid back in 2005 actually has a one in 2700 chance of hitting the earth in a latter quarter of the 22nd century that may sound high but that's still a 99.97 or 96% chance of not hitting the earth but by going to an asteroid asteroid like Bennu and studying it at least thermally and trying to figure out how do your Kofsky effect is pushing it around we can update and refine the models we use for predicting other potentially hazardous asteroids in the future. And then Rex, regular explorer. Regular is kind of sciency speak for dirt. It actually comes from the Greek it's called the Greek meaning is blanket rock it's basically the fine material that covers the bedrock so on earth that would be soil that would be dirt and be volcanic ash. On the asteroid it's the fine particles and of course not only did we characterize most of the surface of the asteroid it's this regolith that we will eventually be taking back to earth. Again true a lot of missions of Cyrus Rex is a collaboration between a number of different groups. We have the University of Arizona which is running the science team. NASA Goddard which is doing the overarching management as well as running a lot of things like helping with navigation and they've contributed an instrument. Lockheed Martin was the aerospace company that built the spacecraft and then we've got other smaller universities not smaller universities but other universities like Arizona State, MIT and Harvard that contributed instruments and then there's a private company called Kinetics and they're the ones who do a lot of our navigation so they're ones who are really flying the spacecraft through the solar system around the asteroid. And we also have significant contributions from the Canadian Space Agency who contributed an instrument and CNES which is the the French Space Agency. Now Cyrus Rex is what's called a PI-led mission or a competed mission not all a lot of missions NASA there's kind of the scientists NASA and Congress get together and decide we're going to do a sample return mission from ours or we're going to you know send Cassini to Saturn. But they also have two programs one of which is discovery and the other one is new frontiers where they ask the astronomical community to submit ideas for a mission. And in 2004 we submitted our first proposal at the time it was just Osiris it was very much a bare bones mission it was just to sample collect their head and a camera and we submitted it to the discovery program and the discovery program has produced a lot of the planetary missions that we're you know that we've seen over the last couple years going all the way back to near Shoemaker and Mars Pathfinder in the late 90s the most current one is Insight which is on Mars and then there's two extraordinary missions Lucy and Psyche that will be launched in the coming years. So we submitted in 2004 and didn't get selected in fact no mission got selected then we submitted again in 2007 and we made it to phase A you can almost think of it as like the finals the playoffs we were one of three missions that were selected ultimately Grail which went to the moon to measure the gravity of the moon and the internal structure of the moon was selected but we decided after kind of losing out on discovery twice that we needed to bump up to the next largest category of mission which was New Frontiers and New Frontiers was has produced New Horizons which of course went to Pluto here he's back and then flew by Erika which was a Kuiper Belt object Juno which is currently at Jupiter and then Osiris Rex in 2011 and 2012 was selected as the third New Frontiers mission and since then an additional mission Dragonfly which is going to be flying a cop there around Titan was selected so thanks to bumping up to the higher New Frontiers class we were able to take that bare bones Osiris concept and really flesh it out with a lot of great instrumentation that helped characterize the asteroid that's really where the Rex comes in it was kind of a joke that you know the new proposal was Osiris Rex it was a step further than the old proposal like any like most spacecraft especially if you're going through another body you've got cameras so we've got a series in fact we have six cameras not counting the star trackers that are on this mission three cameras are considered science cameras they were developed at the University of Arizona one is Polycam which is a 20 centimeter eight inch aperture though it's it's fast it's about an f3 so you can kind of think of it as your c8 except for one of those night owls from star azona plugged in there it's a 1k ccd field of view is about 0.8 degrees and it's designed for not only observing and detecting the asteroid when we were far away but also as a focus mechanism that gets us down to stay in focus down to about 200 meters off the surface so it also was our kind of zoom in camera as well when we were doing close flybys at a surface unfortunately for to make things a little less risky and the minimize moving parts our cameras either have a focus mechanism or a filter wheel and for pan cam we went with the focus mechanism so it only has a single panchromatic you can think of it as a luminance filter stepping down the size we have map cam which is a basically it's effectively 125 millimeter f3 telephoto lens this one we didn't have a focus mechanism instead we had a filter wheel and again we had the luminance filter but we also had a b and v filter we had eight actually they were part of the eight color asteroid system and the b and v is the same as the johnson b and v that a lot of you probably use for you know variable star photometry and asteroid tree and then there were two other filters that go out into the red w and x that were primarily their placement was designed whereas it was optimized to differentiate between different kinds of asteroids and in the filter wheel we actually put in a little diopter kind of like a little eyeglass little reading glass in there so we could actually image the surface at 30 meters when we were dropping down to the surface and the final camera was sam cam which is a much smaller instrument has a 20 degree field of view and it's really designed for just imaging the sample head as we actually collect stuff off the surface we also have three navigators f cam nft cam and still cam in fact still cams sole purpose is just to take pictures of the sample return capsule and you'll see pictures of us actually stowing the sample within the sample return capsule and the other two were one was designed nft cam to actually map the surface as we were descending so there's like train recognition software running on that and f cam was kind of the workhorse for taking pictures of the stars and the asteroid every two hours over almost the entire mission to make sure we knew exactly where the spacecraft was with respect to the asteroid so as it turns out nft cam turned out to be a pretty important science instrument as well we have two spectrometers we have a visible and infrared spectrometer which covers the visible wavelengths starting at 0.4 micron so basically again your b filter out to around four miles you also have odys which is a thermal spectrometer which kind of takes starts off where ovaries let's off a little bit of a gap at around five six micron goes out to a hundred micron so it really is taking the temperature of the asteroid ola which was our caution from the canadian space agency is a point laser altimeter and it was able to as long as we were within about seven kilometers of the asteroid it could detect the asteroid and it can run at rates as high as 10 kilohertz and it's got a mirror so it's actually wasn't just pointing directly down it was actually scanning and scanning across the surface of the asteroid so rotating is a map of the surface of the asteroid not so much an image but a combination of millions of these range points that were taken by this instrument and then the last instrument is rexis which was actually a student built instrument we had a competition for various universities around the country to come up with a student instrument to go on a cyrus rex and they built in a regular what they call the x-ray imaging spectrometer so it's looking at some now the asteroid itself admit x but if they're a flare you'll actually get luminance of material risk and that will actually be able to be detected by the by the instrument and the movie i'm showing there was them they actually detected a x-ray outburst from a black hole which was kind of cool so why ben new now the reason why we went there is because we wanted to go to carbonaceous asteroid but why that carbonaceous asteroid when we were making this decision back in 2005 there were about a half million asteroids that were known but you didn't you couldn't go to all of them because most of them are orbiting too far from the earth it would take too long require too large of a rocket just too much money to get to so you go to near-earth asteroids those objects that do come close to the earth and that dropped that number of 500 000 to about 7 000 but even of those near-earth asteroids most are in most are in orbit set again taking too close to the sun too far from the sun there's too much inclination again it's too much of an effort to get there so if you only want to go to those objects that have what we call low delta v orbits that don't take a lot of energy to get to you're now under 200 and most of those objects in earth like orbits are way too small they were discovered followed for a few days and are now lost or if we still have a track of them they're rotating too fast some of them are rotating less than a minute like that and for something rotating so fast is even have regular thumb or did it all get thrown off so now you're down to about two dozen and at the time a lot of those objects weren't characterized so there are only five carbonaceous objects that we knew of and it really came down to two asteroids Ryugu which is where the Japanese space agency just went through with Haibusa too and Benu and the reason why we ultimately went with Benu was because we actually knew what its shape was because we had radar observations from the NASA Goldstone telescope and the Aerocebo telescope so had it not been for those radar observations maybe we would have gone to Ryugu and the Japanese would have gone to Benu if we were to do this exercise now there's a few more carbonaceous objects that have been discovered and characterized in the meantime but it's really not a lot of objects you can go to and these objects are not big I mean Benu is only about a half kilometer across and that's like less than a third of a mile so it's not a large object as you can see it's not much taller than the Empire State Building when you compare it to the the recent small asteroids that we do like Yidakawa at the first Haibu submission went to or Ryugu at the second one went to you can see Benu was actually a lot smaller than Ryugu and if you took Yidakawa and you kind of smushed it from that sausage shape into a you know a dough ball it's probably smaller than Benu so Benu kind of fits in the middle when you compare these objects to all of the quote unquote small bodies and a lot of planetary astronomers consider small bodies to be almost any asteroid or comet I mean Benu and Ryugu are right here much smaller than even 67p which is the comet that the Rosetta mission went to and Ceres and Vesta don't even make the cut on here but they would actually be five to ten times larger than this large object here in Letitia so we launched the Osiris Rex mission in September 2016 and then we we were in a one-year orbit flew past the earth in September 2017 and that gave us a nest of a kick being Benu's orbital plane and then we slowly caught up and the first image of the asteroid was taken in August of 2018 we spent the next couple of months in what we called our approach phase as we were getting progressively closer and closer to the asteroid and then we kind we considered our arrival December 1st of 2018 and that was when we were no longer approaching the asteroid but we were starting to do maneuver either going at the orbit or doing maneuvers around the asteroid to observe it at different observing circumstances observing it at different phase angles or different solar times so for much of 2019 we were in this alternating back and forth between going at the orbit as well as maneuvering around the asteroid and then the latter half or last few months of 2019 and most of 2020 was doing what we called reconnaissance and rehearsals where we had picked our sample sites and we're now making very close flybys to get higher resolution as well as practicing the descent down to the surface and then we finally got made our sample collection almost a month ago October 20th of this year now when we're orbiting or flying by the asteroid like I said before the asteroid small it's only a 33rd of a mile across 500 meters across we can get really close in fact most of our orbits were within about one and a half kilometers of the asteroid and some were down to about 0.8 kilometers and so and even at such a small orbit a 0.8 kilometer orbit still takes you 24 hours to go around it this graph there's you know venue small and doesn't have a lot of gravity when we were out at 1.5 1.8 kilometers it took almost three days to orbit the asteroid and our orbit I should have put a shown a graphic there but our orbit was what we call the terminator orbit so if the sun is off to the side we were actually orbiting in the terminator of the asteroid and the reason for that is that's actually dynamically stable if you have your solar panels pointed at the sun you will actually have a balance between solar radiation pressure forces and the gravity of the asteroid if you're going in front of or behind the asteroid solar radiation pressure will start pushing on the spacecraft elongate the orbit and ultimately you'll end up crashing into the asteroid so we always went into a terminator orbit which was nice and stable so for the first few months we started approaching Bennu and we had all these ground-based observations we had these great radar observations one of the reasons why we picked Bennu is because it looked like its surface was benign we knew there was one big boulder and you can actually see it rotating right there Ben Ben and there wasn't much else and we thought from the thermal inertia observations we got from Spitzer as well as the radar observations that the surface was probably pretty flat had lots of fine material wasn't going to be rocky and we've seen asteroids fly by and we pinged them at radar and there were boulders everywhere but as we closed in you start going uh oh there were rocks everywhere on this thing and there wasn't the nice little pliers that we saw on some of the asteroids like Itokawa and Eros which were like these almost sandy beaches and as we zoomed in and got closer I mean there were rocks and boulders everywhere in fact one major region of the asteroid we just kind of informally called boulder town and you look in there and you go well geez where is any of the fine material and how do you get close to an asteroid like that and collect any sample so that was the first real surprise that this object contrary to the ground-based observations was a lot rockier than we really were expecting and now this is the part of the talk where I start presenting a lot of the really cool science that we produced on the mission so we knew Bennu was going to be a dark asteroid we knew from the ground-based and the Spitzer and Hubble observations it has an albedo of four percent on average four percent is dark that's that's a few times darker than fresh black top and that's about the same albedo as coal so it's a really dark object so it was kind of surprising when we got there that there were you know okay dark boulders but they're also brighter boulders and in some cases really bright boulders and that was a bit of a headscratcher we knew the asteroid was slightly blue it was a b-type asteroid and b-type asteroids are by definition when you do the spectroscopy slightly blue most asteroids are neutral or red but the b-types are blue but even when we looked at the surface of Bennu we saw evidence of red boulders and red material and so it does look like what we're seeing here possibly is the different colors and the different albedoes are really telling you something about the age of the material not so much the age of when it formed and the grand history of solar system but how long has it been on the surface of the asteroid so if the average terrain which is this light blue and we think that means surface that's on average at least greater than 200 000 years old or has been on the surface from more than 200 000 years old that the first thing that happens to it is it slightly blue ones it actually gets brighter and turns blue but it turns out the freshest material is actually the red dark stuff and what we're thinking is going on here is that if you took a shovel you dug down into the regular Bennu you would uncover red material and so the red material we are seeing on the surface is stuff that was just recently uncovered perhaps by a landslide perhaps by a meteoroid impact producing a crater and you can actually see where the craters themselves the fresh small craters have this little red hume so this might actually be a red hue this is actually probably the material that's been on the surface for the least amount of time the other interesting thing is we saw a series of boulders some of which were quite bright i mean many times brighter than the dark material and they had a different look like they were made of a different mineralogy in fact it looked like they had pyroxene in them and pyroxene is an igneous rock and Bennu should not have had any kind of volcanic activity at any time in its history i never should have gotten warm enough for that so what exactly was creating these really bright boulders that we're seeing as it turns out spectrally these actually match the spectrum of Vesta which was the second largest asteroid or third largest asteroid it's definitely the brightest asteroid in the main belt and Vesta was just recently visited by the dawn spacecraft and so Vesta lives in the inner solar inner main belt we think Bennu came from the inner main belt as well so it's very possible that when Bennu was either in the inner main belt or possibly part of a much larger asteroid that then broke up that at some point pieces of Vesta you can say contaminated this carbonaceous object now our best understanding of how Bennu got to where it is is that it originally formed in a much larger maybe 100 kilometer 200 kilometer asteroid in the inner solar system carbonaceous and maybe as that asteroid was going around the sun for the first couple billion years of the solar system it was collecting basically debris sweeping up debris that was falling on it and some of that debris was pieces of Vesta this large object must have been destroyed at some point because it's not there anymore and also would explain how Bennu got liberated but it's possible that impactor that came in and hit the primordial Bennu parent body was a piece of Vesta or at least had Vesta-like qualities and what would happen is the asteroid would be shattered and then the smaller pieces like Bennu would actually re-accumulate from the debris that had been released by the impact so when the impact happened it didn't just throw out a big Bennu piece it threw out a lot of little pieces and then Bennu formed from that so if the impactor the impactee was carbonaceous the impactor was related to Vesta the new re-accumulated Bennu could have pieces of both or it's possible that you just had impacts from vestoid pieces just falling on the surface as Bennu was spending the next half billion years or so in the main belt before it was finally kicked into the inner solar system now what's interesting is we kind of should have expected this you remember back 2008 there was a 2008 TC3 which was an asteroid that was discovered by the Catalina sky survey right before it hit the Earth's atmosphere and actually landed in the Sudan it was picked up as the Almohada set of meteor fall and for an object that was only about four meters across so it wasn't very big the thinking would be well it's all going to be the same kind of material but in fact it had a bunch of different meteorite types within it so it was a breccia or a conglomeration of a bunch of different meteorite types so it must have originally been on the surface of a larger asteroid and all these types just kind of these different meteorite types kind of got merged and melded together and and so that was the first sign that okay maybe these objects aren't quite as homogenous as we were expecting it also turns out we probably knew this in 1969 because there was a famous fall just across the border here in Mexico called Allende and that was a carbonaceous asteroid but even among that fall they were finding meteorites that didn't quite match the type and at the time there was a question of well is that what those meteorites related to Allende or maybe it was something that fell in the distant past and as people are looking for the fresh fall they're finding older stuff as well so it does look like there's been a lot of mixing and matching of different types of asteroids and stuff in the solar system we definitely are detecting evidence of surface changes on the surface we've seen large craters we've even seen small craters almost like you know you're getting a little shotgun blast on a surface of a rock and it was kind of cool because you can actually count the craters on what should have been a fresh surface and derive how long that surface has been there as well as how long the asteroid has been in the Earth's space and the current estimate is that Bennu left the main belt little under two million years ago give or take half a million years or so so it's been spent about two million years in the inner solar system and we also see evidence of mass movement we're seeing where boulders have shifted we're seeing where material is burying boulders and a lot of that movement seems to be shifting from the higher latitudes to the equator one of the biggest surprises of this mission was a week after we entered orbit and this was actually one of my discoveries I was flipping through the navigation images and one of my prime responsibilities during approach was to look for satellites look for cometary activity not only for science reasons but because it could be a hazard to the spacecraft especially when we're flying in close proximity and during that approach we didn't detect anything unusual not surprising we didn't see anything in the radar data even though we know a quarter of all the Earth asteroids have satellites that means three quarters of them don't so not surprising we didn't see anything and then all of a sudden I'm flipping through the data and I notice what looks like a star cluster sitting right off the northern limb of the asteroid and these images only go down to six seventh magnitude so and this is a 38 by 44 degree field of view so you would in you know as you're flipping through you'd see the familiar constellations go by there goes Orion there goes Lyra you'd see the the beehive so it was a star cluster I never recognized so I was basically using my backyard experience here so of course what do I do I pull up Stellarium and I go okay it says we're pointed here and it was in Hydra I'm like well there's no star cluster in Hydra it looks like this nothing this large and then after a while I finally was able to realize that most of these stars aren't stars and then when you stretch the image especially here you notice that as you get far away from the asteroid these little points become more and more elongated like they're streaks moving away and when I you know just sat there in DS9 and drew lines back to the surface realized they all seem to converge or emanate from a point on the surface so here was evidence that something just happened on the surface of venue something was actually throwing off material so perhaps this was an active asteroid and active asteroids are objects that we think dynamically as well as spectrally shouldn't be comets they should have spent most of the history of the solar system in the main belt close enough to the sun that they should have been thoroughly baked through or pretty close to that so they they shouldn't have ready reservoirs of ices that would produce cometary activity and yet these objects do show evidence of some sort of activity and just to show you kind of how busy the asteroid is every once in a while you'll see a major release of particles you'll see a particle kind of fall into a temporary orbit and stay there for a couple of days but then crash back down on the surface and we're estimating that about 10 kilograms of material is ejected from venue every venue orbit and it takes 1.2 years to circle the sun about 30% of that material escapes venue completely doesn't fall back on the surface it goes basically creates a benewed meteor stream behind the asteroid now that may sound three kilograms of material every year or every 1.2 years they sound like a lot of material it's actually not if you actually take that rate and assume it continues into the future it would take much longer a few times longer than the age of the solar system to completely erode away venue but it does suggest that even these inert asteroids are shedding material they are acting maybe comet like and so as I said you know active asteroids are comets formed outer solar system a lot of ices gravitational perturbations kick them back into the inner solar system you have dust and gas out gassing creates coma and tail the active asteroids should not be active and there's a lot of different reasons for why they might be active and in the past there's been suggestions and maybe they are really like comets there there still is some ice that significant amount of ice under the surface and that's sublimating and creating more traditional cometary activity we have seen objects that look like they were just impacted by something you know like Sheila is a good example here's an object that's you know tens of kilometers across probably got hit by something a few meters across and what we saw is the debris that was kicked off that asteroid the rocks themselves might be cracking take for example venue it rotates every 4.3 hours so that's a lot of thermal cycling a lot of the rocks you know expanding and contracting every 4.3 hours as you hit the thermal cycle and that is actually weakening the rocks and of course it's a microgravity environment so if all of a sudden your rock pops and forms a crack you can throw material off and even escape the asteroid some minerals themselves might just be thermally disassociating because they heat as well there's electrostatic levitation we're just because of solar wind and stuff impinging on the surface you can actually build up a charge and this has been seen on the moon and should occur on asteroids as well where you get electrostatics that levitates particles off the surface and then if you have another force it can kick those off as well and if you get close enough to the sun and we've seen this with Phaethon which is the gemmated meteor apparent body you can have the solar wind is dense enough it could actually sweep across the surface like a wind and blow stuff off the surface and then finally we have objects that just they spin up they rotate too fast and they actually disrupt and throw material off the structural integrity of the body fails and it throws material off and in some cases it completely disintegrates and breaks into smaller pieces we did a real deep dive study on Bennu and what was causing this activity and it does appear that it is most likely due to meteoroid impacts and thermal fracturing this thermal cycling rocks probably both a really recent result and the fact you may have seen some new stories just in the last week is thanks to these particles because they're nice little gravity test particles in orbit around the asteroid we were able to really accurately measure the internal structure of the asteroid itself and what we're finding is that the core region as well as the equatorial bold region are actually less dense than the rest of the asteroid and we're not 100% sure why that is it's possible that the equatorial region because material is moving down from higher latitudes and it turns out those particles preferentially crash into the equatorial region as well that you just get a accumulation of material and because the object spinning not quite a breakup velocities but at least at the equator there's less gravity just because it's centripetal forces that you just don't have packing and so you've got a less dense ring and as for why the core is less dense we're not really sure it could be because at some point either it's a relic of Benny's formation it formed that way or at some point in the past it did spin up and a lot of material left the core region and move outwards so as I said before once we got into latter 2018 and into 20 sorry latter 2019 into 2020 we started doing a lot of these flybys and we dropped that once we had picked our sample sites we started doing what we called recon passes like for example recon see we got down to about 250 meters which is about 800 feet and even did some rehearsals where we dropped down to about 130 feet off the surface and we had selected we had a whole kind of March madness kind of thing where we started with I think with 16 potential sites down selected the eight picked our final four and then from that final four we went with our primary site which we called Nightingale and these are all bird names because the asteroid venue is actually a bird from Egyptian mythology and our backup site which was Osprey and just to kind of put in context the size of this it's not a lot as you can see it's a few parking spots and that blue circle was the bull's eye we were aiming for and what we did with the spacecraft is it actually did have terrain recognition software on board so it didn't actually control the spacecraft but what happened is the spacecraft was ascending it's kind of like throwing a dart at a dartboard and it was taking pictures of the dartboard as it's going in and if it notices that it's on target it will continue if it were to notice that it weren't wasn't on target and was going to actually end up tagging a dangerous part of surface it would have aborted and we would have tried again but luckily everything worked on that first try and so the spacecraft did not land on the surface what we did is we we called tagged it touch and go we dropped and if you can remember the old car air filters the round ones you drop in screw down that's what this is this is one of those old car air filters you drop it on the surface there was canisters of inert nitrogen gas that would then blow through blow into the surface mobilize the reguleth which would then be caught by these little catches that are in the side there we only expected to be on the surface for a few seconds so this is the video of sam cam centered up on the head of the head of the tag arm as we descended then as the canisters blew this is a little longer image this is actually the nav cam as we start descending to the asteroid and this took about four hours as you can see we're moving around shifting things and about now actually spoke too soon there there's a little flat region there is our sample site we start descending closer and closer and as we get really close you'll start to see the shadow of the sample head there it goes and all chaos breaks loose and after about five six seconds on the surface the thrusters engage and we back off and pretty much everything you're seeing in this image and I will actually go to the next slide because I cut out the beginning stuff so we can kind of keep playing the really interesting stuff here almost everything you're seeing in this image is the breed that has been kicked off the surface finally when we get far enough away down here you can probably see the asteroid surface through the debris and what we're thinking is that there's these dark regions are probably shadows the debris is kicked up it's casting shadows on the surface the shadow up here is from the actual tag event itself and then there's four thrusters on the four corners of the spacecraft and each of those probably scoured the surface and we think this shadow here was due to basically the debris being kicked up by one of those thrusters and they kind of give an idea of the field of view here so this is only about 10 meters across what you look this orange circle and then we've got the red field of view this is for SAM cam and the green is the field of view for NFT cam there so everything kind of makes sense there's a boulder here that's starting to appear from the field of view here comes the head itself you can see NFT cam was offset from the head itself then we slowly start backing away you got a whole bunch of material that's tumbling and even this bright rock here is still something that's sitting there above the surface tumbling maybe it's fallen just on the surface but as you can see it shouldn't be there so this is something that we had kicked up and then landed somewhere else on the surface now the plan for a cyrus rex was to collect at least 60 grams of material it as it turns out we collected probably a lot more than that because to our surprise we were going to do a whole bunch of what we call mass measurements one was to just like the image you're seeing here take the sample head and you take a picture of it you just look do we have material inside there does it look like it's dirty does it look like it's actually collected something and then we were going to do a moment of inertia test we've already done this with the sample head empty and then we were going to do this and just kind of do your little moment inertia and try to figure out how much mass you've actually collected but as soon as we started taking images of the collector head we started noticing there was debris just falling out of the collector head so we had so much material that it was actually overflowing the sample collector so we decided well you know what we're going straight to stow we're not going to do any more tests and we think what happens going back to this video you'll see there's a little flap mylar flap that opens to let the material in and that flap should close so much material is collected that flap was wedged open so every time we were moving the collector head around now we were losing material and as you can see here this is an image of us stowing the sample collector head into the sample return capsule if you look closely you can see small particles coming off so there was still stuff falling out of this as we were stowing it but luckily everything worked and it stowed successfully and there's a nice picture of a closed capsule so what's left for the mission the Bennu encounter phase the science phase at least the asteroid science phase is over so there's no more science collection currently planned we're still in the vicinity of Bennu we're you know tens to hundreds of kilometers away and slowly drifting away with time and we will be there for a few more months before we actually do a maneuver and start our trip home and ultimately the samples will be turned to earth in september 24 2023 and then at that point just the sample return capsule lands on the earth the spacecraft itself will fly by the earth and who knows the spacecraft is still in good working order the other than the fact that all the instruments have a nice coating of Bennu dust on them they're all still working so maybe we will actually go somewhere else go do we can't get samples from another asteroid but we can go visit another object if NASA wants us to do that and just to kind of close out the talk especially since everyone's into amateur astronomy here we did and it was mentioned earlier on we have the it was a target asteroids program which was run by cyrus rex and the target neos program which was part of the astronomical league now that those cyrus rex the science is ramping down everything's going over to the astronomical league and where it can continue the project of trying to enable people with you know relatively modest backyard equipment using ccd's and cmos detectors to do photometry of either asteroids similar to Bennu and Ryugu similar near earth asteroids or to do photometric observations of those objects that might have been parent bodies the objects like Bennu and Ryugu that are sitting out there in the main belt and you know we publish our papers in the minor planet bulletin and usually we combine all the data we get in order to drive colors get rotation periods face functions i've been trying to get more and more folks using star analyzers to do spectroscopy which i mean honestly you can only do it on the brighter objects but still there's plenty of good bright carbonaceous mean belt objects out there as well and of course the mission like i said isn't over we still are going to be producing great science from tag we still have the sample return coming in 2023 as well as all the great ground analysis that will be done on those samples and hopefully it'll be an extended mission for a cyrus rex as well so we've got all over social media like most missions on our website so definitely come and visit us and thanks for having me all right well thank you so much this is a really great we've got a lot of really good questions here so let's get right to the questions and so i i don't know if you want to stop sharing or maybe you want to leave it up and then be able to go back to help answer the questions yeah it might be good just leave it up because i can't go back to a slide if i have one so let's um we'll kind of jump around here a little bit some of these are related to each other and so ron asked at what point did you realize that benu was more rubble than rock and what was your reaction so that was early on during that approach phase um as the you know the asteroid was growing from you know one pixel across the 30 pixels to 100 pixels 300 pixels we quickly realized that this object was a lot rockier and bolder than we were expecting and it there was concern there was a wonder that would we actually be able to deliver the spacecraft to the surface and collect something and originally we were not going to use natural natural feature tracking we were going to drop down to the surface and we wanted to look for something a clear spot that was at least 25 meters across there was no part of venue that we can land where it was safe across the entire 25 meters and that's actually that large circle that you're seeing here so natural feature tracking was actually developed in order to ensure that we could land on a much smaller footprint successfully and it worked so yeah it did drive a lot of developments the fact that the asteroid was less benign than we were expecting okay so kind of sticking with the same general um i guess topic ted wonders uh so where did all the fine material go was it there and got tossed off or just never present that is a good question um it's possible it could be related to electrostatic levitation like we mentioned as a possible cause of these particles the reason why we didn't see any electrostatic levitation is because it's so efficient that it's already removed all the fine particles as soon as they're being formed they're being lofted off the surface and removed there's actually some idea that these objects are fairly porous and maybe find material as the asteroid shakes that falls into the surface and it's the bigger stuff kind of like what they call the brazil nut problem where to find material if you shake a can of brazil nuts the smaller pieces fall down the bigger pieces rise to the surface so maybe the fine materials inside the asteroid okay steven asked and i i think it's related here is the rate of loss of material off of asteroids considered static linear or non-linear as of ages could have measured loss rate in a single year then be used to date the object it probably well i'm not sure it's going to change with age of the asteroid though it does change with its position in the solar system closer you get to the sun the higher velocity of these meteoroid impacts as well as the hotter the surface gets so thermal fracturing becomes more of an issue as the asteroid were actually to start eroding it would get smaller and smaller so you'd have less surface area being impacted or less surface area having thermal fracturing and the gravity would be less so there are changes and we did think that we did detect a drop-off in activity as we went out from perihelion and aphelion though that's just a suggestion from the data we can't really prove it yet but it's unlikely that we could use that to actually age the asteroid just because there's all these other factors and forces that would actually change the particle rate okay so stan was wondering why would the material preferentially accumulate in the equatorial region so now you're asking the question would i'm not an expert in oh maybe that's the maybe that's one of the big research areas to discover that it actually was yes i was one of the first things that the uh our radio science dynamicist actually did notice one part is that because i mean that is not obvious when you look at this picture but the equatorial region does stick out furthest from the asteroid so you've got particles that are in close orbits are coming close it would preferentially run into the ridge itself and it would start building up i wish i could give a better more insightful question of like i said i'm not a dynamicist okay so richard asson so kind of sticking with the sample site will the team make an effort to observe the sample site to see how the surface was disrupted after the contact yeah i really a lot of us were hoping that that would happen um the decision was made i mean the the goal of this mission is to collect the sample and return it safely to earth and once the sample was collected and now that we're backed away from the asteroid we've done the risk analysis and decided that it's probably not worth the risk to go back closer to the asteroid and image so at this point in time there are no plans to do that but it would have been a great would love to have seen that observation so i know that uh so blaine is wondering and i know that you probably you know you filled up the uh the sample containers but uh and you had how much you were anticipating but do you have any idea of how much material was actually collected to bring back to earth oh i mean we you know we're aiming for 60 grams we know the sample head can collect up to about two kilograms so we're thinking we definitely have hundreds of grams i don't know if we got two kilograms but we got quite a bit that's a good to the amount yeah i mean that's a couple pounds yeah yeah that'd be really good so that's um you know joe asked this actually an interesting question was there any damage to the spacecraft during the collection the only damage and if you call it damage is that we did notice that a lot of our instruments are less their sensitivity has gone down so our optics are coated with venue dust not a lot but you know factor two at most so that's the only real damage haven't heard anything from the spacecraft as whether the panels themselves are coated i'm assuming they would be but no real damage other than the fact that you know you just took a leaf blower to you know a dirt pile right next to your telescope and you probably wish you hadn't done that okay so joey asked why why was it they used new nitrogen to loosen and um to vacuum up the sample because nitrogen is inert it doesn't react with anything so the nitrogen wouldn't actually react with any of the material on the surface and wouldn't contaminate it or change it in any way okay and so in thinking about the compositions then linda asked do you know what the compositions are of the dark boulders and the bright boulders a lot of that is going to have to wait until we actually get the sample back and even when we zoom down to uh you know very high resolution you can see bright flex and dark flex mixed together so when that sample comes back you can't really tell a lot from spectroscopy you can tell a few things like we can tell that the surface was hydrated that there actually is water attached to a lot of these minerals the surface has lots of uh organics and carbonates but you and of course we saw a pyroxene but it's hard to tell the exact mineralogy from the spectroscopy and the photometry so a lot of that is going to have to wait till we get the sample back and uh so dan was asked actually very early on what analyses of the samples will be done once we have them back on her oh just about anything you can do to a rock um the plan is the initial plan was you know you collect 60 grams and we were only going to study 20 grams and the other or 15 grams and the other three quarters of the sample was going to be put in storage so as new techniques are developed new instruments are developed we can actually study those at a later time but some of the things we hope to do is not only determine what venue is made of but also do like radioactive isotopic analysis can we measure exactly when venue material formed you know goes back to the early solar system but also a lot of these radiotopic clocks get reset when there's a traumatic event so the hope is that we'll you know have a bunch of material that goes back four and a half billion years and then we'll have a bunch of material that was reset when venue's parent body was disrupted that impact that caused the release of all these small carbonation subjects maybe we'll even have evidence of not catastrophic but major impacts on the surface so the hope is that using these radioactive isotopic analyses we can really figure out what this asteroid's been doing for the last four and a half billion years so once we bring the samples back so chris internet asked how will contamination be avoided on the return to earth right so one thing we had in the sample return capsule actually in the head in the sample return capsule actually i think it is in the sample return capsule is what's called the contamination plate so this is a plate that's been exposed to space and there will be contaminants i mean the fuel that we use the hydrazine is a contaminant and i'm sure the hydrazine got all over everything it's probably all over that asteroid now so you do have this contamination plate so you can say okay the things on this plate are stuff that accumulated over the course of the mission heck probably accumulated even before the spacecraft was launched when it was sitting on the rocket in florida or when it was sitting in the the bay there at kennedy space center and so by recognizing the contamination you see on that plate you can then go okay the things we're seeing there we can disregard within the sample but once it lands i mean it's hermetically sealed there should be no air or water getting into it when it lands in utah in september 2023 and then immediately we pick it up fly at the johnson space center and use their their curation facilities the same facilities that go back to the holidays okay so we're getting close to the end here i think we're going to go for uh two more questions and i apologize to everyone we've got some really good questions here but uh you know we're not going to be able to get to all of them and so um let's you know these are kind of some interesting ones we had uh we'll kind of lump on robert was wondering what is the gravity of this asteroid and then mike and jinkee were wondering how much would a 150 pound person weigh on beno oh well i can tell you it's microgravity it's 10 to the negative fifth earth gravity earth gravity it's really really small so those particles that we're seeing being thrown off the surface just to give you an idea the escape velocity the average escape velocity from the surface of benu is 20 centimeters a second that's it so if you were on the surface and you're throwing a baseball not only would you throw the baseball off the surface you'd probably kick yourself off the surface as well i mean completely out of orbit wow yeah so we had several questions this would be the last question and and so uh several work kind of alluded to this was uh how this osiris wrecks um compares and complements the haibasu uh missions and so how are those working together to you know kind of compare notes so to speak yeah so we've actually worked very closely with the the haibusa team um in fact it helps that our principal investigator danti loretta learned the japanese when he was an undergrad so he actually can you know and so the first haibusa mission went to the asteroid itakawa which is an ordinary chondritic asteroids and s types a completely different type of asteroid than the two carbonaceous asteroids that we went to an interesting thing about yugu and benu is that dynamically and if you even look at their shape and sizes there they should have formed in the same part of the main belt in the inner main belt so they could be related asteroids they could actually be from the same parent body but there are differences the colors are slightly different and like i said before benu is hydrated it shows evidence of water at least trapped within the crystalline structure of the minerals on the surface yugu is bone dry so here we have two objects that look like they should be dynamically and physically look like they should have formed in the same part of solar system maybe even from the same kind of objects and yet one has water and one is dry and maybe that's telling us something about the different evolutionary paths they took over history to solar system so it's very complementary to go to multiple objects because just because you got on the one doesn't mean you know everything all right well thank you so much carl this is absolutely wonderful and really timely we had a good crowd here and i think that we counted between youtube and the people here on on zoom we had probably in the neighborhood of 250 people out there maybe more so we probably had multiple people at each site and so thank you carl for joining us this evening and thank you everyone else for tuning in thanks for having me yeah so you'll be able to find this webinar along with many others on the night sky network website in the outreach resources section each webinars page also features additional resources and activities we'll make sure that this presentation is posted on the night sky network youtube channel it should already be there because of live stream but it will also be up on the night sky network web page within a couple of days as well join us for our next webinar on thursday december 17th when robert nemeroff will share with us highlights from the astronomy picture of the day archive for 2020 that was one of our more popular webinars last year and so robert is joining us again this year to share with us the best of apod for the year so keep looking up and we'll see you next month and we're still here but um this is fantastic so this is uh um you know it's going to be interesting to see um you know to keep following and and to you know it's going to be exciting for the the capsule