CAS October 2020 Virtual Meeting: Meteorites

[Music] [Music] my name is jim kuka i am president of the chicago astronomical society welcome to our october general meeting our speaker tonight is mark hammergren the title of his presentation is meteorites through space and time mark um worked as a planetary scientist at the adler planetarium for from 2001 through 2020. his research focuses on investigating the composition of asteroids using reflective spectroscopy a technique that measures mineralogical absorption signatures in the spectra of reflected sunlight from asteroids um mark is currently president and ceo of his own um uh company called farther horizons and um we um welcome mark and um mark if you can just take it away and uh educate us thank you i think mark might be frozen for a second here he's frozen in time okay there we go okay that's much better uh before we do get started i am going to just quickly uh mute everyone i'll ask mark to unmute yourself um once that's done and then uh while the while the presentation is going on um if you have any questions please feel free to type them in the chat um and then i will enable unmuting once the presentation is over and we can have time for questions right afterwards wonderful well thank you very much for the introduction jim and i'm very happy to sorry mark i actually muted you as well [Laughter] and again thank you for inviting me i'm happy to be here tonight and uh this has been an exciting week for asteroid related news we had the touchdown and sample retrieval from asteroid bennu near-earth asteroid bennu by the osiris-rex spacecraft i will briefly mention that later on and we can talk about that after the talk but without further ado i think i'll get started with the presentation here i'm going to share my screen and bear with me for one minute so my talk tonight is really going to be a very personal story it's going to well start in my childhood and go forward through time and explain why i'm interested in these flashing lights in the sky and stones that that fall to the ground occasionally from them my childhood inspirations some of them and you might recognize them yukon cornelius from rudolph the red-nosed reindeer he's a prospector up north so i was interested in rocks like most kids are flying saucers here we have earth versus the flying saucers very interested in ufos and flying sausages again the possibilities of alien life carl sagan one of the world's greatest science communicators was a great influence on me in high school particularly when cosmos came out and raiders of the lost ark this uh i was also very interested in archaeology and to be honest treasure hunting so i i really found something i think that combines all of these interests and i remain interested in them today now you might remember some of these images from the 1953 george powell movie war of the worlds starts out with these giant meteors coming down this is of course based on the h.g wells novel some wonderful iconic alien invaders less iconic alien invaders are the meteorite that hit gilligan's island and imbued the residents with special powers now as fanciful as those are these are based on real phenomena to some degree and they can be very beautiful and considered art pieces in their own right this is an iron meteorite a chunk of iron mostly iron some nickel that fell in 1947 in the siberian forests knocked down a swath of forest you're right you might know it better as the meteor crate by the way let me let me know if i'm i'm breaking up here i don't have my chat window pulled up but again you see this beautifully sculpted exterior this piece in particular weighs over a thousand pounds and is not affixed to the tabletop if you ever visit the adler uh i used to tell kids that if they could pick it up they could take it home but i stopped doing that because you'd get a group of them gathering around it and try to shift it around and i was afraid they would pinch their fingers and historical interests too this is the willamette meteorite it's an iron meteorite that was found well i would say found in uh in oregon it was known by the local native americans for ages and ages and they collected rain water out of the pockets and used that in uh ceremonial uh for ceremonial purposes now of course when westerners found it they sold it to the american museum of natural history in new york and dragged it back there where it was on display and for a long time people could climb in it more locally and this this uh really piqued my interest back in 1928 a meteorite fell in southern illinois not too far from saint louis the small town of benold and that was interesting to me here we see uh poor mr mccain whose uh brand new 1928 pontiac coupe was struck by a meteorite and if you look closely at he looks like it was a very sad face back then there was not the same degree of collecting of meteorites as i saw when i visited the field museum as a kid is the very same exhibit that you see there today about this meteorite the meteorite and it really no pun intended struck me as being fantastic that space could reach out and here on earth so they have various fragments or various artifacts of this meteorite fall on earth the study meteorites in more detail and just a very quick introduction to meteorites meteorites of course are rocks that fall from space the very most common kind are these kinds called ordinary chondrites they make up more than 70 percent of all meteorites that fall to the earth they're ordinary for that reason they're not ordinary in the sense of ordinary earth rocks uh but they're the most common kind they're mostly made of silicate minerals and throughout with nickel iron fragments and let's uh gives its name the chondrites is they have these little glassy beads spec throughout the interior and you can see some poking out on the exterior of many called con drools and when i say glassy these are the results of melting of interplanetary dust during the formation of the solar system these are among the oldest things in our solar system and in a sense meteorites are sedimentary rocks collected together in the vacuum of space another kind of uh chondritic media right has chondrules that you can see in this image as little it's this is a cut through the side of it you can see little white circles chondrites are particularly interesting because they were not heated very much during the formation of these meteorites and their apparent asteroids and that means that the is made of clay-like minerals which is the result of silicate minerals being altered by water and so some of these can contain up to 20 percent of their mass in the form of water they also contain organic material that is not necessarily formed by life but containing organic molecules things containing carbon hydrogen oxygen nitrogen even complex ones like amino acids and it's thought that carbonaceous chondrites would have supplied the early earth with some of its water that we find on its surface as well as the organic material needed to be the building blocks of life iron meteorites can be some of the more interesting looking ones and i think some of the more interesting kinds because think about where we would find a huge mass of iron on earth and you might think iron mines that kind of thing but that's not native metal iron this kind of nickel iron we would find in the core of the earth and indeed most of these iron meteorites would have been formed in the cores of large asteroids large enough that they would have been completely molten and had the heavy metals sink to the core and the lighter molten rocks the lava flowed to the surface now how do we get iron meteorites out of the cores of asteroids you smash them together asteroids have been smashing each other to dust since the formation of the solar system you cut iron meteorites open you polish them you etch them with acids and you can see these distinctive crystal patterns metallurgists do this on earth to study the uh well the metallurgy of human-made iron the crystals formed the crystals in iron meteorites are so big that it means i might be stuck here the crystals in iron meteorites are so big that they indicate a cooling rate of something like one degree every million years or so stony iron meteorites are also very interesting they can be the most beautiful samples of them they consist of a matrix of this nickel iron with rounded crystals of olivine known as also known here on earth as the semi-precious gemstone peridot and if you slice these very thin you can see through the crystals so often these are displayed backlit by light so that you can see the the transparent crystals okay here we come to a formative event for me when i was early in graduate school this is the second year of my uh stay in graduate school the peak skill meteor was seen flying across the northeastern united states a very long trajectory came in at a very shallow angle here we see the meteor itself breaking up came in on a friday night during homecoming football season so actually not uh boy just uh just around this time in in 1992 so many people caught it on video cameras because they were out there filming the football games that enabled scientists to track it back into space and get an orbit for it but also it's special because it ended up coming down in peakskill new york meteorites are named after where they where they fall frozen up a bit mark okay so it it fell through her chevy malibu and i later saw this car and the meteorite itself in a glass case in paris france during an international astronomy conference so it uh is definitely and it remains i'm sure the most valuable 1980 chevy malibu in existence during my time at the adler planetarium a very very interesting event was the fall of the park forest meteorite march 26 2003 march 26th as a date is important to me nowadays because my son was born march 26 2016 13 years later on that same date but here we see a view of the incoming meteor it was probably about two meters across it's about six feet across and this view is from about 100 miles away from south haven michigan and it came down in the south suburbs of chicago and one of the places that was hit because this is a populated area and fragments of these meteorites came down all over the place one hit a fire station other houses would hit but this one hit the house of phil and brenda jones in olympia fields punched through the roof into the dining room bounced off the dining room wall punched through the dining room floor went in the basement bounced off of a rock and landed in a pile of lawn society connection the the biggest police i'm sorry mark but you are breaking up to the adler planetarium okay i'll repeat the biggest piece was donated by audrey and greg fischer to the adler planetarium and there on the right hand side you can see a little bit of the linoleum floor that was uh embedded onto the meteorite when the when the meteorite hit the floor we now know for a variety of reasons that most meteorites come from asteroids um a handful of meteorites relative handful fewer than 30 nowadays have been actually recovered and tracked during their passage to find out what their orbits were every single one of them takes their their way back if you track them back in time into the asteroid belt between mars and jupiter now a very few of them a very small fraction have been identified as pieces of the moon or mars but the vast majority come from asteroids a little bit about asteroids most between orbit between mars and jupiter in the so-called main asteroid belt more than a million asteroids have been discovered to date uh most of them very recently since the advent of the digital revolution the largest of these asteroids is asteroid number one the first one discovered ceres which is about a thousand kilometers or about 600 miles across and we don't know what the smallest ones are because they're too small for us to find but they probably we know for a fact actually they go all the way to the size of dust grains and there are probably more than a 1.4 million asteroids in the main asteroid belt larger than avatar interesting for a few reasons are those that do not orbit in the main belt but whose orbits bring them close to earth and in some cases in some cases actually hit the earth and more than 24 000 of these near-earth asteroids or near-earth objects have been dis to date not all of them the vast majority are not hazardous only the ones larger than about 100 meters across are big enough to punch all the way down through the atmosphere and pose great danger to the surface a couple pictures of asteroids asteroid bennu small near-earth asteroid a little bit larger than the empire state building across and of course much more massive this was and is the target of the osiris-rex uh nasa mission which touched down briefly on the surface of this asteroid and did a and go sample retrieval and they'd i just heard a little while ago from wayne that they recovered something like two and a half kilograms which uh some of it which was composed of larger fragments that they intended which is kind of jamming open the sample container so they're gonna try to close that up and and make sure they can bring that stuff back it is a sample return mission another sample return mission of the asteroid gu was by the japanese hayabusa ii mission and it sampled the asteroid last year 2019 and it is actually on its way back to earth and should return to us in december so that'll be very interesting to see the materials from these two asteroids now part of this talk is going to be about meteorites and history and mythology one of the more in recent pieces by recent i mean in the middle ages is this uh really funny thing i think people in braunschweig germany in the middle ages they believed that bright meteors were dragons flying through the air and if they stood under the eaves of their house and yelled out fire dragon share with me the dragon would drop stuff like treasure or a big ham or for the unfortunate a big pile of excrement so that explains why they would be standing under the eaves of their house you don't want to get hit by any of those things a little more previous to that actually for thousands of years an example of a human interest in meteorites is the cape york meteorite recovered from greenland recovered again that's a kind of a generous term uh robert peary the explorer was led to the meteorites by a local inuit and the locals there had been using these iron meteorites hacking off pieces and using them as native pieces of iron to make things like harpoon points so they were actively using them in their culture to make tools because humans oh well think of it first of all in greenland what are the local sources of iron none and uh also smelting of iron by humans out of iron ore was not discovered was not developed until something like 2000 bc ushering in the iron age so for most of human history metallic iron the only source of that was iron meteor arc that contained pieces made from meteoritic iron including the iron that this iron dagger from the tomb of tutankhamun and if you look at even the linguistics you see a connection this is the set of hieroglyphs for the egyptian word ba and pet means metal from heaven that's that's the word for iron metal from heaven it's entirely possible i think of course it's not recorded and it's entirely possible that a meteorite fall was observed by people who then recovered iron fragments from that and made that connection now the ancient babel babylonian word really meant about the same thing so this was spread throughout the region now this is going to be a little bit more speculative here the ancient egyptian benben stone that's uh the pyramidal capstone so pyramid-shaped capstone to the to the pyramids this in some cases these would be made of solid gold the ones that survive today are made of polished stone and they were believed to represent the rays you know rays coming down from the sun or specifically the seed of the sun god in stone form the petrified version of these things and it's speculated of course we you don't have any first-hand reports dating back from that that this may have been inspired by oriented meteorites oriented meteorites retained their orientations the name suggests as they fall through the atmosphere which gives them this kind of pyramid shaped or conical shape like a heat shield shaped form and it's thought that you you can think about that bright ray coming out of the sky even in the daytime if you have a bright enough meteor and then when it lands you see this chunk of rock petrified what is this and the connection between the sun god and meteorites is apparent well it's it's thought that maybe the extension of the ben ben stone inspired the shape of of the pyramids themselves but i was going to say that the most influential story in egyptian mythology is their creation myth the creation of the world through the pregnancy of isis by her brother osiris and it's the coffin spell 148 one of these inscriptions after the blast of a meteorite such that even the gods fear isis awoke pregnant by the seat of her brother osiris so we have and uh i don't know if you can you can see but there's an alligator in the top line there and that word there yeah right in the middle of the the top line of hieroglyphs and that little alligator shaped determinative that's part of the word for meteorite imagine an alligator snapping forward the swift motions of an alligator other cultures dating back even before the egyptians worshipped stones that they believed to have fallen from the heavens this was put forward brought forward by the ancient greeks the ancient hebrews people through the near east and even the from all of the lands that they conquered they tried to collect all the holy items this is uh reminiscent of uh raiders of the lost ark these expeditions going out to retrieve these things and on some of the ancient roman coins you can see evidence of uh the temples that were uh dedicated to the worship of these conical stones conical stones that were called baitly or baitalis and there are a number of different coins that show that here's here's another temple uh the temple of adana said biblus showing one of those conical stones in there again possibly oriented meteorites now the ancient greek beetholos in the ancient greek is the an iconic which means not representative uh not looking like a representative of a human to be actually a god itself or the residence of a god now that's kind of weird why would a why would a funny-shaped rock be thought to be the residence or or a god itself um maybe if they saw it fall from the sky or if it looked like something that fell from the sky and we even see a reference in the bible in the old testament genesis 28 jacob's ladder now i i don't know if you know that story but he's out in the desert and he lays his head down on a stone and he has this vision of angels going up and down a ladder in the heavens and when he wakes up he says among other things and this stone which i have set up for a pillar shall be god's house and this is the origin of that later greek term betalos the house of god in in israel in in i'm sorry in hebrew is beit el so imagine a corruption of that term into ancient greek and then into ancient latin so this is from the sky and representing god's org god uh dates back very early later on uh the idea of a beetle of a residence of god was also combined with the idea of what's called an umphalos a belly button stone the center of the world things that included the oracle at delphi here we can see one of these conical shaped stones in all cases they were conical shaped stones or more fanciful versions of them you even see them integrated into later christian structures the church of the holy sepulchre in jerusalem there the very on the right at the uh towards the bottom you can see the umphalos stone in the church of the holy sepulchre meteorites were also also revered in the ancient americas we know that not necessarily by records but by evidence the casas grandest meteorite a large one and a half tone me ton meteorite was discovered wrapped up like a mummy in a burial vault and in arizona the camp verde meteorite weighing 135 pounds was wrapped up in a feather blanket a very elaborate feather blanket and put inside a burial chamber a burial cyst and you wouldn't do that for ordinary rocks just sitting around there these were very very important things to them and so clearly there was some special significance associated with these stones and i think this story i think is is very timely again it's speculative but very secure deals with the leonid meteor shower now meteor showers like the leonids are not do not arrive uh to us from asteroids but rather comets they're bits of debris from comets given off during their passage by the sun and currently the leonid meteor shower occurs in the middle of november 17th 18th of november and outbursts meteor storms can occur roughly every 33 years not like clockwork necessarily sometimes you miss one of these uh apparitions but sometimes you get thousands and thousands of meteorite the meteors falling per hour just an incredible incredibly dramatic appearance to the ancient aztecs this was known as the falling hairs the meteorites were meteors where the falling hairs the fall of sonte mocha and this the the leonid meteor showers were supposed to be accompanied by the lord of the dead and this led to the timing of the aztec festival of the dead when the deceased can visit the living this might already sound familiar to folks and the timing of this festival and at the meteor shower itself occurred back in the 1500s by the time the spaniards arrived in late october now not mid-november because the of the procession of the equinoxes the very slow turning of the pole of the earth which causes the seasons to vary during the time of the year and so what happens in late october that is related to the festival of the dead now this is disputed by some historians who think that this is just a more recent re popularization of the time of this in the 20th century for mexican nationalism but i think that even in that case it builds off of traditional beliefs that were integrated into christianity during that syncretic period of spanish occupation and even more recently this is a very interesting part of my own personal history the impact of asteroid 2008 tc3 discovered by my friend richard kowalski working at the catalina sky survey and here we see how asteroids are remote usually found if you take a series of images of the night sky pointing in some direction where you don't know anything really is and you look for something that's moving against the background stars so this asteroid was automatically discovered richard confirmed it made sure yeah it's a real thing measured the positions of it sent it into the minor planet center and then got a notification back that it was on a collision course with earth you can imagine the feelings that that would inspire actually the government was notified about that so the next question is when is it going to hit less than one day notice now that was i don't know i would say it's not very fortunate but it also implied that given how faint the asteroid was and how close it was to earth it was also very small so probably less than something about five meters maybe 10 to 15 feet across any damage should it hit the earth would make an awesome fireball and its position was so well known as it came in that they could predict where it was going to hit within just a few kilometers and indeed in the early morning hours of november i believe it was or was that october october 6th very october 7 very early morning hours a bright fireball erupted over the skies of northern sudan this is the nubian desert and as the sun rose the next morning people in wadi alpha the border city between egypt and sudan saw this really crazy smoke trail in the sky this is dust blasted off ablated off the meteorite as it fell through the sky and it's twisted into these crazy shapes by changing upper atmospheric winds only was it seen from the ground but also infrasound low frequency sound measurements detected it impacting in the atmosphere uh infrared satellites weather satellites detected the flash in the sky as it came in and again the idea was that you could track its passage through the atmosphere and figure out where it would have fallen on the ground and indeed that's that's what was done and later that year an expedition was mounted and fragments of the meteorite fragments of this small asteroid were recovered and here we can see one of the early maps red dots show where the fragments were nubian desert and the closest point of any kind of habitation was station 6 almahata sita which is a train repair station one year later a conference was held in khartoum sudan at the university of khartoum and because i was working doing research on asteroids of the very same kind i was able to travel to khartoum to attend this conference and present some work i had done on asteroids of that type and here we see many of the local faculty attending one of the sessions i i found it very interesting that here in sudan more than half of the faculty were women in in the sciences and after the academic conference we took an expedition to the impact site to do our own search for meteorites so we started out in the capital of khartoum and we traveled on a road that was paved for about maybe three quarters of the way a little bit more than that a journey of about 500 miles the last hundred of which though are in the sand sea of the nubian desert following along that train line which connects khartoum to egypt and along the way we stopped at some historical locations and this is the mountain the very small mountain of jebel barkal and the temple of amun where you see us walking through right now the temple of amun in ancient is it was the center of what was then a universal religion it's where the pharaohs of egypt at that time up to ramses ii were coronated and here we are traipsing through it and as someone interested in archaeology myself i was both fascinated and horrified that almost anywhere we walked there would be kind of a crunching noise the crunching of us stepping on pot shirts little bits of broken pottery and everywhere i went i could pull up things like this dating back three thousand years four thousand years in some cases just under foot here we see a decorated piece of pottery look down and here's a piece of metal work ornamental metal work just laying there on the ground uh archaeological treasures laying there because they just really don't have the resources to conduct site preservation or uh further excavations of the site and of course this being sudan and these being treasured national uh nationally significant items there's no way i was gonna you know pocket any of these things oh well let me let me fill up and take these things home because uh yeah i'm not gonna end up in a sudanese prison these are the vehicles that we use to travel across the sand sea i called them at the time adventure buses i swear they had almost no suspension and once we got off the paved roads i mean the potholes were bad enough and you think the sand is going to be relatively smooth but holy cow we were bouncing up and down very bad so for about a hundred miles i had to stand in the bus hold onto the back of the seat in front of me and ride it like a bucking bronco and we would get stuck sometimes in the sand because a very fine sand everybody'd have to get out and we would have to push well i was off to the side not pushing you could only stack so many people up and we went into the night this is one of the range rovers accompanying us and starting out at something like six in the morning we finally arrived at the site at about three a.m at which point we had to set up our tents and my tent is the one in blue there to the uh to the right my trusty family tent which i humped all the way to sudan in the middle of nowhere and uh that building behind us is the single bathroom for this entire site uh all of these buildings were built by the british during the reconquest of sudan in the uh towards the early uh 1900s late 1800s and you can imagine basically a a pit toilet that has been filling up for more than 100 years here in the daytime is our site and this is the train repair station refueling station we went out into the desert and we painstakingly lined up for a systematic search and there was an attempt almost at military precision stretching us out so many feet apart okay stretch a little further and then go so we're standing there around for about a half hour or so and then go let's you know do a systematic search and everybody runs off in different directions it was it was a little frustrating that we were wasting so much time but as we went along and here you can see the terrain that we're looking through some hills in the distance we don't want to search those places other things that we found this was an inhabitable area we were told that there were entire cities entire villages up in the mountains nearby and these have not been excavated and thankfully the locals the few of them that there are in the the nubian desert they don't they don't touch these things here i found this meteorite this is my these meteorites were easy to find because they were you know surrounded by these circles in the dirt you know you just have to no no um once we found one we weren't supposed to touch it we were supposed to just circle it and stay by there for the retrieval team to come one single retrieval team for our entire group of people and so we'd have to stand there waiting and waiting and waiting for people to show up to pick these things up and take them away and then we could look for more meteorites and as you're standing there off in the distance you see oh there's another media right okay i gotta wait now again again easy to find because this one fell next to a dollar bill no um for scale very easy to spot these black stones in places among the white marblish sand another close-up of these things here you see some of the hallmarks of what is still a relatively freshly fallen meteorite the kind of matte black fusion crust and a slightly different colored interior these meteorites had been identified as being a very rare type called a urea light named after uri a location in russia a differentiated type of meteorite they're again made by processes that completely melted the meteorite of the parent asteroid and these ones uh the urea light meteorites contain a substantial fraction of their composition in the form of tiny tiny micro diamonds this one i think is very cute it's about the size of a pea the sand grains next to it so we found you were able to find things this small and this unweathered because of them falling in as a desert during that time i was lucky enough to find eight fragments altogether our team the entire team we found about 40 fragments of different sizes and so this was a an incredible experience for me and so if any of you are familiar with the classic movie the treasure of the sierra madre but uh you know when when the prospector finds the gold deposit without even telling his companions he just goes crazy and starts doing this happy prospector dance and uh you know i used to be i still am in raw counting and every time i find something really cool or if i find some gold specks in a river i have to do the happy prospector dance so i find my meteorite and i have to stand there and i have to do the happy prospector dance and uh let me tell you it was an incredible experience and here we come to the end this is my friend richard kowal from the catalina sky survey uh he is still very much active as an observer at that program and he is also notable not only is the discoverer of asteroid tc3 but also the second and the third known asteroid to hit the earth all of them very small uh so went to earth and one of them fell in the middle of the atlantic ocean the other one in in southern uh south africa so um i will leave it there and open up for questions all right thank you so much mark uh there have not been any questions in the uh chat just yet um although bob plow does say that that meteorite at the adler is his uh because he has a picture from when he was 10 years old in 1964 of him touching that meteorite um and so bob if you do have that picture and want to share it please feel free to do so the rest of the participants you are free to unmute yourselves if you have questions or you can drop them in the chat and i will relay them to mark as well this this is bob actually i think mark helped me get that picture i've got that old view master reel and i contact i think i met mark at some adler presentation somewhere he put me in touch with adler's archivist and they digitized those pictures and sent me a cd so i'm going to click on share here for a moment and you can tell are you saying that now so you can tell that's you master reel do you see my mouse moving in the picture too yes indeed yes yeah so you it's a square picture and it's got those rounded corners so that's i don't know if mark goes back far enough uh before all the adler expansions that was down in the basement under the the dome room and they had the cutaway image of the crater sitting there wow and they sat me under those floodlights for about an hour getting that picture during my winter coat indoors oh boy and you remember that you know what the rule is when you're 10 years old if your hand is on something right if you touch it it's yours right oh so i maintain still that that's my meteorite on display there um we do have a couple of other questions in the chat um for mark the first one is from alan uh there's a chicago store that is advertising meteorite jewelry that is carbon dated to something billion years uh perhaps they pick something that the public would get instead of saying usable dating methods is that common heard of something like that before carbon dating carbon dating specifically is not usable on meteorites carbon dating relies on the proportion of carbon 14 isotope relative to carbon 12 and it's a radioactive isotope generated here on the earth by the impact of cosmic rays just uh radiation impinging on the earth and that decays on a relatively short time scale relatively geologically speaking thousands of years time scale so you cannot date something billions of years ago by carbon dating but you can use other radioactive isotopes um uh thorium lead uranium these kinds of isotopes have uh billions of years in some cases uh decay times so you can use those to date those meteorites yeah is probably what they're confusing on and then also tracy asks um are there any precautions that you should take when dealing with physical specimens precautions so um that works both ways if you're talking about being worried about health no meteorites are radioactive they're not made of poisonous materials there's really the greatest threat from a meteorite is oh you froze up a little bit here mark really okay sorry you froze up right when you said that your greatest threat from okay dropping it on your foot dropping it on your toe if it's big enough if it's big enough that's right i've got i've got a bunch of tiny ones too in which case your biggest threat is dropping it on the floor and not being able to find it again now the other way of looking at it is what should you do to preserve meteorites a chunk of rock like this that is covered with a patina from the desert is not going to be terribly affected by my handling it but if you have a fresh meteorite or of you know a nice polished iron meteorite your skin oils can impart things like salts and moisture which will cause rust and will corrode meteorites over time oh and also one other thing uh the iron meteorites they do contain a few percent nickel and some people are allergic to nickel and there are jewelry tests of nickel and some people use them to try to figure out if something's a meteorite or not so that's the only that's the biggest problem uh kind of related to that and from my own curiosity um when you were talking about your experience in the desert um you had to draw the circle in the stand and wait for someone to come over uh because you weren't allowed to touch them uh and the reason i was just curious that the reasoning behind that was that just so that you don't put it in your pocket and walk away with it or something no not not so much not so much you know uh the idea was that i don't know if i'm freezing up here again but the idea was that we wanted to preserve the chemical integrity of the meteorites we don't want to touch them and import impart anything like organic molecules from our skin any oils that kind of thing so that these would be as pristine as we can we can get them now that was something of a croc though i have to say because after taking such long precautions uh and wasting so much time honestly we get back to khartoum and the sudanese leader of the expedition he's carting these things around in plastic okay they're wrapped up in foil but loosely wrapped and then in plastic shopping bags in the back in the trunk of his car which is stinking of gasoline fumes and not only that but when he has these in the lab he decided it was very important to measure their densities and that's a marginally interesting property of a meteorite but instead of packing so how do you measure the the density you measure the mass and then you measure the volume so the density is the mass divided by the volume how do you measure the volume well you're not going to put it in water to see how much it displaces most places who do this they put the meteorite in a container of tiny glass spheres tiny glass sphere rules and you measure the volume displacement there he didn't want to do that though so he just had people sweep up his lab floor in the hallway and collect all of that dust and dirt and put it in beakers and drop the meteorites in there and cover it up and there was an active they were actively painting always so um you know talking about organic materials organic compounds in these meteorites it was just a you know after all of our precautions i would not trust any data coming uh out from those studies so yeah we had a had another question i think pop up yes uh from alan um he said uh and the meteorites big enough to hurt us and projected impact dates uh for that and so i'm going to paraphrase a little bit off of that um relating to what you had said from your friend who found the asteroid with the one day notice projected impact date it being relatively small um kind of going off alan's question here are what is the danger of a you know one that can actually physically cause harm to a person or a structure and we don't know about it or we find it you know with a day's notice or something like that right right well we we had a very uh a very notable example of that several years ago over russia over the uh western siberia city of chelyabinsk a meteorite a chunk of rock ordinary chondrite as a matter of fact uh somewhere around 50 feet across 50-55 feet across came in uh at a very shallow angle and it broke up into thousands and thousands of fragments millions of fragments really the largest of which was a few feet across fell in a small lake and no damage was caused on the ground by any of those fragments hitting anything but but rather the atmospheric shock wave the the blast of air from that meteorite coming down and blasting through the air at hypersonic speeds caused tremendous damage in the area mostly in the form of shattered windows but more than 1600 people were sent to the hospital with injuries mostly from broken glass and also people hurting themselves as they hurled themselves away from the from the blast coming in um oh i think we lost you again for just a second here oh okay you seem to be back now yeah okay so yeah so that was about again about 55 feet across air blast will be the major source of damage up to things that are about maybe a hundred feet across uh majeed as the follow-up question um could be how long in advance do we usually learn about these meteorite impacts so there are vastly more small ones than big ones which means that most of the ones that are discovered in general are very small anywhere from maybe only a few meters across to maybe tens to 100 meters across and these are discovered with at in most cases only a few weeks notice in every case where one has been discovered prior to impact it's been within a few days of impact with uh if not a couple hours of impact larger asteroids their orbits can be known for in in the best most exquisite cases up to a thousand years in advance we can track them and determine whether they might hit or not but after about a hundred years or so going forward into the future the orbits are chaotic enough that we cannot determine whether an impact will occur or not no definitive impacts are known to be uh on the on the radar screen for a long time coming well uh forever we don't know of any okay and uh john asks if you would elaborate on the process of determining the direction of origin of meteors uh especially considering that different sized objects may encounter different amounts of atmospheric resistance uh so do you take that into account when you determine their direction yes absolutely to some extent although the atmospheric resistance isn't as important as you might think and that's because when we see when you first see a meteor entering the atmosphere in almost all cases that's at altitudes of about 100 kilometers or about 60 miles high and so much of the path the early path of a meteor in the sky is relatively unaffected by the earth's atmosphere you do see that drag later on especially when fragmentation occurs but when you see that early path you can really just follow it through the sky you have to have at least three different points of view to triangulate where it is at a given time but then you can you know as you watch it come down you can track it backwards in time a bigger effect than atmospheric drag is the gravity of the earth so you have to do what they call propagating the position of that you have to include the effects of gravity as it had pulled it on the way in then you can track it out into space and take into account things like the well the the gravities of the sun and the other planets and the moon wonderful john says thank you um does anyone else have any questions for dr hamergrin well it's been wonderful to talk to you tonight yes thank you so much hang around for a couple minutes as long as you are wayne um uh sure we i don't really have too much else i don't know mr cooper if you have anything you wanted to add um i am more than happy to stick around uh for as long as you would like uh for questions and things like that um but yeah it's entirely up to you yeah this is jim um uh hello guillermo i haven't talked to you for a while we hope to have a zoom meeting in november we don't have a speaker a date set up but please stay tuned and we'll um once we get a speaker lined up we'll uh send out the word we'll have it posted to our website and we'll have put it on facebook and and of course cernan will do the same so thank you so much to mark hammergren and uh to everybody who participated thank you so much very interesting thank you

Channel: Cernan Earth and Space Center

Views: 3,347

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Id: e-6ga-VZnHg

Length: 58min 44sec (3524 seconds)

Published: Thu Oct 29 2020