Ep. 780: When Asteroids & Comets Attack!

0:00Oh Assarami cast episode 780 when asteroid and comet's attack. Welcome to Assarami cast for weekly facts based journey through the cosmos where we help you understand not only what we know but how we know what we know. I'm Fraser

1:00Kane. I'm the publisher of university with me as always is Dr. Pamela Gay. I seen your scientists for the planetary science institute and the director of CosmoQuest. Hey Pamela, how you doing? I am doing well. I am deeply confused by what February could bring us in terms of rockets and very very sad that I went on vacation which means that I don't have the ability to go watch rockets. By the time people are listening to this in theory, Artemis 2 could launch within days of when you're listening. So we're looking at Artemis 2 we are looking at new Glenn 2. We're looking at a variety of other rockets because why not? There's a whole bunch of stuff around the globe that's pioneering this month. I'm gonna try and stream a bunch of it and you usually do interviews with Scott Manley and I forgot the other humans names. Yes and those interviews are wonderful. Go check them out humans. It's we're going back and

2:03I'm really feeling like Blue Origin is going to be able to deliver Viper and that's what I'm really excited about. It feels very bizarre to me to put these words in a sentence. Blue Origin launches rockets. I know. And yet they appear to be doing such a thing. Yeah slow and study. Yeah well slow we've been I don't know if it's steady or slow. We have been reporting on their launch delays for almost my entire journalism career. That's fair. Yeah. But look at where Starship is and it's feeling kind of like the turtle in the rabbit right now. Yeah I don't know. Let's see we'll see we'll see. I'm hoping both cross the finish. Yeah. Yeah. I mean New Glenn is not a fully reusable to say rocket. It's only using the first stage. Yeah. SLS is a non-reasonable rocket in every way shape or form. But it is a monster while Starship is the one that is he's actually trying to make full reusability function and they're having their

3:05challenges as well. So we are definitely in the in the cutting edge across the world of you know China is is rushing forward. They're trying it too. They're trying with the reusable. Yeah. With reusable rockets as well. So yeah everything is going to be changing. But we're not going to talk at all about rockets today. No. No. We live in a cosmic shooting gallery. It's on the matter of if but when dinosaurs blah blah blah you know the drill but seriously folks it's raining rocks and ice out there. How seriously should we take it? What happens when a variety of different objects hit the earth? We'll talk about it second but it's time for a break. And we're back. So you know we think about objects in space. You know I'm just like right now everybody's listening to this. Imagine an asteroid in your mind like just like picture that asteroid. You know the worst science fiction is filter brain with what an asteroid looks like. Okay great. Now imagine a comet again. That's a little better. Yeah. But

4:06still possibly not completely accurate. Now we're going to sort of explode all of those preconceived notions about what these things actually look like and what they might what they might do to our planet if various ones hit even if we attempt to prevent them. So let's let's just like start with your straight up regular asteroid. Yes. And you know again my you know the audience is probably you know my imagination is okay it's this sort of potato like rock and I sort of think about like arrows and I think about a couple of other asteroids we've got images of. Carbonaceous conduit. Edicawa right. Yeah Edicawa is a great example. It's it's a few hundred meters across. It's cashew shaped. It appears to be a solid object. And yeah so you send that kind of several hundred meters asteroid at the planet earth and you're looking at a global catastrophe.

5:08Right. It is 20,000 megatons of energy assuming your typical impact rate of about 20 kilometers per second. But these kinds of impacts appear to happen about every 200,000 years. Right. That a multi hundred meter object. Yeah. That will call will have global consequences. Yeah. Appears to happen every few hundred thousand years. And like if let's I'm wrong like we're all very familiar with the meteor crater impact. And that one doesn't even qualify for those bigger impacts. Yeah. No. So meteor crater is about a kilometer across that's the kind of thing that you get from something that depending on what it's made of with the density of the impactor is could be anywhere from 50 to a hundred meters. And and so yeah meteor crater was still caused by something

6:12fairly large. But in the grand scheme of things. Yeah. Not that large. And it's wild to consider all the different possibilities. Itaquil is a great great one to consider because it appears to be a fairly solid object. It's the not solid ones that deeply worry me. And that's where we got new images of asteroids from Hybus 2 as well as Osiris Rex. Yeah. And if that looks nothing like that solid rock object that is you know what we see in all of the artwork of asteroids as the dinosaurs are looking up and watching this multi-created thing blazing in the sky above them. So with Benau you have an object that is roughly the density of a ball pit of basically gravel and rock

7:13and boulders loosely held together such that the pull of gravity if you were on the surface you would feel like how a piece of paper feels on your hand. So this is a very loosely held together object. And as it approaches the earth it's going to get loosened up further and further and there is the potential for that to end up being a series of objects impacting our planet depending on how much they get slowed down or not. How much it gets disrupted or not. Yeah. Yeah. So you know we think about this idea of the Roach limit which is how close objects have to be where the tidal forces of the earth will tear it apart into chunks and then those chunks will be torn apart into chunks and then you'll get you know if it becomes really close and you'll get something like a ring which is always a bad day. You never want to see a ring around the earth that is that is trouble. But if it does get relatively close and still going to hit

8:17yeah it will get torn apart as it's getting close especially since it has absolutely nothing holding it together beyond the mutual gravity and there's always done. And so you get it turning into this smear of gravel and various boulders and rocks as the world turns as it returns yes impacted right now on one hand there's the good news that smaller things are just going to get completely obliterated in the atmosphere anything under 10 meters it's not going to hit the surface. But all that kinetic energy is going to end up in the atmosphere and all of that kinetic energy is going to heat up the the atmosphere and our atmosphere becomes an easy bake oven right and and this is not a good way for us to combat global warming. Right of course yeah instantaneously we've got ourselves a problem but but where I think I think about the impacts of

9:18Schumacher-Levy 9 on Jupiter back in the in the late 90s and a tidal disrupted comet yeah yeah tidally disrupted comet sorry 94 it was 94 yeah you see these bruises across Jupiter and so imagine if some rock was getting close to the earth the tidal forces as it was getting closer and closer started to separate it out a bit and then you get this string of impacts across some larger area and so what would have been constrained down to just a single spot boom mushroom cloud yeah big impact turns into this long stream and so when we look at the impacts like meteor crater we know now that actually was a metallic meteorite held together yes but you're that's not going to be the behavior when you look at Bennu or or or you know Ryugu they are what are they 10 how many probably like a kilometer across like 500 and I think 900 there yeah almost a factor of two

10:22difference in size yeah meters yeah bigger yeah it's a it's a shock and hit it on the earth and and this is where we have to start worrying about what is the continuum that we have to deal with so on one end you have we we learned last week two weeks go time has no meaning that the Rubin Observatory has discovered some fast rotating asteroids where you have things that are rotating fast enough that if you stood just inside their surface you'd experience one sixth G so it'd be loosely like standing on the surface of the moon if you're at the equator of one of these naturally rotating holding themselves together quite nicely asteroids they're super exciting so we have these nice solid objects that when they hit can cause catastrophic massive craters and even worse if they hit the ocean catastrophic tidal waves that

11:22can destroy far more area because of how far the the water rushes in if you want to read a it shows its age but it's still good book about this Lucifer's Hammer is one that I highly recommend yeah it gets the science right even though it's an older buck and a guy tries to surf the tsunami wave yeah would you know what happened you know that would happen yes yeah all right we're gonna talk about the support but it's time for another break and we're back all right so we've been kind of rambling around a bit so let's now put it all together you know so let's start with first let's start with asteroids we'll start smallest and go to biggest possible impact that we can envision all right so assuming solid objects here yes up to 10 meters it's just gonna be an explosion in the atmosphere it's pretty around 25 30 meters it starts to be

12:25able to survive close enough to the surface that when it explodes it's like chileabinsk where you end up with the the flash of light that causes everyone to run to their windows which is not what you should do and then the shockwave hits the window shatters it in your face and you go to the hospital do not approach the window when there's a flash of light do not yeah yeah so once you start getting over a hundred meters depending on the substance again this all depends on the density of the object this is where you start to get craters of anywhere from house sized to let's form the Yucatan peninsula right sure but like Tunguska people are familiar with the Tunguska impact level that that's probably an air bursting thing but you're getting a you know five megaton explosion and and crater forming and with Tunguska this is where we

13:28have to start considering composition if you have something that's full of volatiles it's going to behave differently as it heats up and if you have something that is made of carbon and deteriorates and burns up at the that temperature versus something that is iron that just gets slightly melty and crushed and makes it to the surface and ruin someone's day so as we consider is it solid or not if it's solid solid crater if it's solid and dirt it burns up if it's solid in ice it goes boom if it's solid and metal it meets the surface now as you end up with something like we keep finding these snowball shaped contact binary asteroids they're super cool they're barely held together they become two separate objects during this kind of an impact event because the neck breaks it's the reality and so now you have two incoming rocks that depending on how much they separate during impact you can either end up

14:33with very close together craters or you can end up just taking out two radically different parts of the planet and and this is one of those things where the movie deep impact and the movie Armageddon came out just I'm gonna see either weeks or months apart I don't remember but it was the same year months apart for sure same year yeah and and deep impact is like yeah it blew up it's gonna hit a whole lot of places we're in trouble whereas Armageddon is like it blew up we're fine we're safe no deep impact got that one right and and you want your asteroid to stay together and hit land somewhere in the middle of nowhere and just get melty like hit a big desert take out a desert do not hit a glacier do not hit volcanoes do not hit opposite volcanoes do not hit water this is a take out a desert and turn it to glass that would be awesome thank you very much yeah at what point does NASA you know NASA has various scales

15:38that they look at and there's these other sort of international collaborations with the the Tareena scale the Palermo scale and what point do we see like what size of an object gives us 50 meters anything over 50 meters you really start to worry you what gives us like a hemisphere's amount of damage and what gives us global damage okay so anything over 300 meters just average carbonaceous conduit anything over 300 meters is the potential for yeah is Australia would definitely go boom Europe would go boom right probably stretching it for Asia it depends on the size of your continent pick wisely yeah but then once you start to get like one kilometer and about this is where lake does matter global catastrophe yeah yeah 10 kilometers mass extinction right that's that's the dinosaurs yeah every plant on earth lights on fire because of the

16:38rock raining back down the hot rock raining back down yeah it's a it's a very bad day it's interesting um there was a study that where we reported on you know people think will like was this a fossils with glass in the in the gills oh no I hadn't heard that but oh yeah these fish had gone to space right yeah yeah well okay so there's multiple stories on this I I love this far too much I'm sorry I'm gonna geek out and interrupt you all right so it hit with enough force that the shock wave moving through land was able to send at escape velocities land trees and dinosaurs at escape velocities so the first animals to go into space were actually dinosaur era critters right that were very much not alive by the time they reach space yeah then then the shock wave went around the world multiple times massive tsunamis heading up rivers and there are fossils

17:40that have been found in the western part of the United States somewhere that begins with the letter T.I. I've forgotten the exact name of the place um where these fossils are from the day of the destruction where they like found one that had its leg torn off they found fish that had the the glass that formed from the hot materials in the atmosphere in the gills and the fact that we actually found a field of fossils that are associated with this impact is just not something I think most of us thought would ever happen and it has been done and it is amazing okay I'm done squeeing no it's fine yeah you're 10c to being a supervillain is just revealed one more time all right we're going to take out the break all right and we're back all right so we've talked about asteroids let's talk about

18:41comets how are comets different in their potential for destruction it's a whole lot of what is the density and and so comets do include organics they do include gravel they do include dirt all of that is in there but they are mostly volitals they are mostly stuff that is just going to go boom in the atmosphere as it suddenly converts itself from ice to gas which is terrible in many different ways so if you think about it you have something that is again anywhere from tens of meters to tens of kilometers is the range you're looking out for comets um that is approaching the atmosphere and the small ones that sudden increase in volume as solid nitrogen as solid water suddenly goes to vapor and expands greatly that's where your dangers coming from and there's

19:44a lot of researchers who think that Tunguska was a chunk of comet um that just came in over Siberia and as it was coming down it it had that phase change and that's a pressure wave flattened all of the trees except for the ones in the very center killed some reindeer killed a few reindeer hunters and left nothing behind this this is one of the most enigmatic events in measured history where there are photos of what occurred and they have searched and searched and searched that landscape and there's just no chunks to be found and with that much destruction it would have to be complete obliteration which you can get that's really interesting with an air bursting comet right right and I think the other challenge of course is the comets can come in a lot faster so you know you always use that uh 20 kilometers a second for asteroid energy yeah yeah the amount

20:48of energy that is delivered is proportional to the velocity squared and so the the higher the velocity the the more damage can be done a smaller comet can do more damage if it's coming in fast and so think about the interstellar objects like think about something like three-eye atlas and the speed that it was going at some point it was upwards of a 10-kilometer object yeah people were thinking now it's probably a little smaller than that but still going at oh 56 kilometers per second yikes and this is where part of the justification for building the Vera Rubin Observatory was to go out and find the unknowns of these things so it's estimated that there's more than 500 million new earth objects that are four meters and smaller and we've only found a tenth of a percent of them yeah so there's a whole bunch of baby stuff out there that atlas keeps finding just as it enters the atmosphere and obliterates

21:50itself it's estimated that there are 900 one thousand meter or one kilometer or larger asteroids out there and we're only at the 95 percent that's good news it's good but 95 percent is not 100 percent for sure but there's only 50 ish yeah global destructive asteroids in our vicinity that we are not aware of yet that's all and right comments are their own rogue thing yes so the probability of you being hit by a large comet is exceedingly tiny because there's not going to be that many there's not that many getting sent in there's definitely not that many alien ones coming in but there's still the potential and and where we don't know all the details on what's out in the orc cloud waiting to get sent this way you always have to wonder is there a 10 kilometer

22:56one out there waiting to come in is a sedent going to somehow get judges in our direction thank you there's no reason to think that at some point in our orbit around the galaxy a close pass with a red dwarf won't send an asceticized object to rack the inner solar system yes so we have a very long lived audience you all think very good care of yourselves and so do you can you give people a sense of in their lifetimes or in hypothetical lifetimes when they get their robot bodies how often they should expect to see various sizes of impacts so we should expect celibate and score tanguska type things about once a century those are two separate creatures right we should expect a large air burst capable of causing havoc to a city sized area in one form or another yeah roughly

23:56is every century right so so another is a natural peroshima yeah once a century yeah um the others so 25 meters is once every hundred years 140 meters is every 20,000 years wow okay that 1,000 meters one kilometer it depends on what you're looking at 200,000 to 500,000 years so and the dinosaur killer that's like in the tens of millions of years it's it's the 20 to 10 kilometer object 10 kilometer is a hundred to 200 million years yeah yeah when you think about it was whatever 65 million years ago that yeah and it's funny because when you think about the movie Armageddon and the sort of classic you know like how big is it it's the size of Texas sir no there are none there are no like maybe what series series that size yeah the size of

25:05Texas of maybe a large moon of a smaller saturday yeah that says you said said no like there there is nothing that is the size of Texas that could hit us so don't worry about now and if it did so bad you would get the moon you would get you would get an impact so catastrophic that it would that it would recreate the conditions that formed the moon much smaller much much smaller the moon was formed by an impact with something that was roughly marked sized sure still yeah you would get a ring yeah you would get you would I mean the entire surface of the planet would be flipped over it would be mold there would be no bad there's nothing left but you wouldn't get a moon the size of our moon that's that's all I'm saying okay let's try everything right fine the point is like that it did not some astronomer look at no of course the astronomer's been involved in the making that movie at all yeah they had astronomers involved in deep impact in that shows unfortunately didn't get as good a rating yeah yeah so I think it's funny like we were

26:09there and I remember you called me yeah when telly events when off in 2013 yeah when we we've been doing this for a while back then and and you like uh something just exploded in Russia yeah you called me on the phone which is a thing you never do yeah maybe once every three years yeah I get full of the panel like oh oh right and then yeah we got the the telly events and that was a thing and it was amazing yeah yeah yeah yeah yeah again you're super villain good science bad humanity yeah you're super villain side is starting to show but and that was I was whatever it was about 15 meters across like it was it was house sized right compared to whatever was the caused tongue oska and we all experienced it and and it's funny because there are probably two say five meter impacts that happen every year like the airbursts happen randomly yeah and Atlas

27:11is really good at finding them and figuring out where they came down and what I'm loving is we'll get usually a few hours notice and so you'll see things uh often out of Issa of be prepared go watch report your images and then they go find the shrapnel from yes there there is a team from study that was able to take the data from Atlas security camera footage and find the the meteor right in a Nairobi animal preserve and it's just sort of like yeah how how do I don't I'm it's amazing yes uh i mean the where things are right now as you said is we have this defense network where various automated telescopes are scanning the sky multiple telescopes yes and when they detect some object that is on course with earth then other telescopes jump in in some cases automatically

28:15make further observations they then pin down when the object is going to strike the atmosphere and where and what trajectory it's going to take so that astronomers are prepared and can can observe it and so we've entered this realm yeah where like you know how many fireballs have you seen in your life i've seen wow i've seen more than that but i think it's because i got really lucky with the August meteor shower and the November meteor shower right so you can now get a notification as an astronomer to go outside where to look you could even drive a bit to reach the point where the impact is going to happen so that you can watch it it's crazy that we're at this point now that that we can predict these things with enough accuracy that you can go out and watch a fireball on command which is which is just amazing to me on command of us not on command of the fireball we can't yet or no we don't know we can't do that but the point being that that before

29:19it was all random you have to be outside you happen to be looking up now you can know where to go where to look what to see and and it just shows up all right on schedule all right hey notice we didn't talk about at all about how to stop these things but we've talked about in the past it's true you all know that you all know the score all right thanks femella hope for the solid objects to impact never go with the loose ones right hit the good hit the land don't hit the ocean all right everyone thank you very much and especially thank you to all of our patrons this week we would like to thank the following ten dollar a month and up patrons Alan Gross Alexis Andrew Stevenson Arctic Fox Astrosets B-Bob Apocalypse Benjamin Mueller Bob Crale Brett Mormon Brian Cook Burry Gowin Christian Berghold Conrad Haling Daniel Loosely David Boggerty David Rossettor Dr. Whoa Dwight Elk Ironsegraff Fairchild Flower Guy Frodo Tannenbach

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31:27your name in the next set of episodes I will be pulling the names and recording next Monday for February so go hit us up on patreon.com slash astronomy cast. All right thanks for one and we'll see next week. Provide everyone. Astronomy cast is a joint product of Universe Today and the Planetary Science Institute. Astronomy cast is released under a Creative Commons Attribution License. So love it, share it and remix it but please credit it to our hosts Fraser Kane and Dr. Pamela Gay. You can get more information on today's show topic on our website astronomycast.com. This episode was brought to you thanks to our generous patrons on patreon. If you want to help keep this show going please consider joining our community at patreon.com slash astronomy cast. Not only do you help us pay our producers a fair wage you will also get special access to content

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