Ep. 780: When Asteroids & Comets Attack!

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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

Kane. 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

I'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

challenges 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

still 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.

Right. 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

fairly 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

and 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

yeah 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

Schumacher-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

difference 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

can 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

able 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

have 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

with 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

that 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

rock 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

that 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

comets 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

a 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

of 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

itself 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

one 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

is 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

Texas 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

there 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

is 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

make 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

it 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

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