Almost 111 years after the Tunguska Event we answer our first (unexpectedly nepotistic) crowdsourced question about the risk of an asteroid impact, and we try to wrap our heads around just how devastating such events could be!

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Welcome to the Astroholic explains. I’m your host, Chris

And I’m Alfredo, The Astroholic.

This is a podcast where I throw some cosmic conundrums your way,

And I try my best to answer them. Let’s get started!

The question today comes from Francesca Carpineti.

That’s my sister. So I can only imagine what she’s going to ask.

It’s a good question. She asks, can we survive an asteroid hitting our planet? I’m asking for a friend.

Okay. Yeah, that is a good question.

It’s something I’ve always wanted to know. I mean, I guess it depends on the size of the asteroid.

Yes, it depends on the size

And where it hits, I guess

Definitely! It can hit worse places and better places. I think we need to be quite cynical here when we consider the asteroid hitting the planet. It could hit plenty of places in which millions or tens of millions, maybe even hundreds of millions could die. But life would continue to survive on the planet. So let’s look at the most densely populated regions we could think of. Maybe hitting lots of places in the Pacific, you could go from the China Sea to most of the North-East Indian Ocean to the coast of California & Mexico…

If it hit in the sea, though that would cause a massive tsunami, surely?


Wait, are you saying that that is more of a danger than if it was to just crash into the land?

No, I’m saying it that… to create a massive tsunami would still depend on the size. But let’s assume that is not too big.

Let’s say it’s the size of a house.

That is pretty much what fell over Russia in 2013.

Oh, the big green streak that was captured on like dashcam.

Yes. If my pronunciation is correct [it wasn’t, apologies], it was over the region of Chelyabinsk in Russia. That was expected to be 25 meters in diameter, and most of it burned up in the atmosphere. It created just a big wave of material and hospitalized, I think it was just shy of 1,500 people.

Whoa, so was that just from little tiny bits?

No, nobody was hit directly is just that the shockwave was so powerful that just broke glass windows in every building and people were out the window looking at the thing and they were hit.

That’s pretty insane!

But no fatalities!

Well, that’s I mean if there are no fatalities that’s good. So we would need something much bigger than a house. In order to, for the sake of this question, to try and survive.

Yes. So when I think about something hitting and creating a tsunami, we would probably be considering something a few hundred meters in diameter.

Yeah. Okay. How big was the dinosaur endgame?

That was 10 kilometers in diameter and created the crater, I think few hundred kilometres across.

Wow, yeah. Wow. Okay. So maybe we’ll scale it down, let’s say half a size five kilometers across

Five kilometres…

So how devastating that would be for humans? And would we be able to escape it?

In an ocean, it would create huge tsunamis

How big? How tall would the waves be?

Difficult to estimate here on my own two feet but we’re thinking of a huge amount of energy release.

So the shockwave would be more dangerous than the waves?

Oh, no, it’s just that the shockwaves will cause dramatic waves. And I would think that a five-kilometer asteroid hitting an ocean would shake an area of the ocean of hundreds of square kilometers. All of a sudden the energy of the impact affects that area and it’s just gonna spread.

Would that wipe out all see life in that area? With the energy that is released from the impact with that superheat?

Yeah, it would, it would superheat the region of sea and it would also push surface water, depending on, obviously, the depth that it is hitting. But you see ‘life finds a way’.

My God stop shoehorning that in every given opportunity!

But it’s true. It’s like for example, hurricanes are terrible for life on earth. And for sea life that gets sucked up and spun around, but it also oxygenates deeper levels of the sea which leads to more life!

While we’re still on the subject of asteroids crashing into the sea: if the energy they release superheats that region of sea, is that something that marine biologists have looked at or noticed, for example, if an asteroid crashed into a reef, surely the superheating would kill that reef, it would bleach it. Is that like an indicator of an asteroid impact? Even far back in the past, if they come across just a patch of white reef.

I don’t think that’s possible. If you, dear listener, don’t know what bleaching is, it’s pretty much the death of coral. The little polyps, the symbiote that lives inside the corals died because of usually few degrees hotter water for a long time.

Yes, it is not a big increase in temperature

No, and this is what is happening to barrier reefs all over the world because of the climate crisis. Increasing global temperature.

[Back to the question] That is, pretty much, dying coral. I don’t think that there is any particular thing that, and I could be wrong, paleontologists could try to search for that indicates a major impact in the past.

I would say that reefs tend to be moderately close to land and moderately in shallow water. So, it is possible to find evidence of ancient impact… Again, depends on how quickly, especially in the sea, how quickly things get eroded. Just think that finding evidence of craters, it’s very difficult. We only recently found out that there is a crater in the UK, for example, and it was an ancient crater, it’s in Scotland, which is quite fun. So back on the effect of a five-kilometer one hitting land… it will be bad. Like in the sea, in any ocean we would be looking at billions of people dead and dramatic release of water vapor into the atmosphere that will affect the climate.

Are we looking at a ‘the day after tomorrow’ kind of situation?

Sorry, I don’t think it would be that apocalyptic in the ocean and to be honest, the Earth is covered 70% by the ocean so that is the most likely place for a hit. I think that water vapor will create lots of clouds. But it will probably quickly rain back down.

What about contingency plans for cities? Like test scenario runs of what would happen if an asteroid was coming for Beijing or New York?

Yes, there actually are. NASA, few international partners like the European Space Agency, and a few federal agencies actually had been running simulations of impacts for years. And it’s not just put stuff in a computer and say” hey, how much destruction are we going to have?”

That sounds more fun. That just sounds like a video game.

Yeah, but it’s actually a tabletop exercise.

So it’s more like D&D?

Yes, in a way. It’s a doomsday scenario D&D, and it’s “let’s assume that we discover an asteroid and it’s coming in X number of years. Can we stop it? Can we divert it? And if we cannot what’s going to happen on Earth?” It’s always fun because obviously they want to pick densely populated regions, which is not obviously going to happen.

It’s not impossible.

No, absolutely. But for example, in the latest exercise, they had the asteroid aiming for the metropolitan area of Denver, Colorado, and then they deflected the asteroid and they ended up pushing it on New York.

Oh, so they tried to divert it away from Earth but they just slightly nudge it…

Yeah. It’s too easy to have the scenario that everything works well. So obviously, they had this scenario in which the potential trajectory of diversion will take it from Denver to New York, and across the Atlantic all the way to the Sahara. And they only changed it that little bit. So the idea here was to push it enough to just skip Earth and I think originally was a 300-meter asteroid and when it was then hit and deflected there was just a fragment.

What effect would that have had on New York? So what did they say would happen? Was it all fun and games?

Not if you’re living in New York. So, in the scenario, the deflecting split the asteroid and now there was this fragment between 50 and 80 meters, which was going straight for New York. And the assumption in the simulation based on the type of asteroids so the type of asteroid is a big pile of rubble, which is quite common in asteroids. And in the simulation, it was going to explode about 15 kilometers above Central Park.



So we’re looking at a shockwave?

Yeah. Okay, with an energy of 20 megatons.

I can’t quantify that. What’s that? Like?

A lot.

I can guess that.

Well, the Hiroshima atomic bomb, which is unfortunately the thing that we always compared to these high energies was 15 kilotons. So that would be 1000 times more powerful or more energetic and would level every building in 10s of kilometers radius.

Wow. So okay, so it would utterly destroy New York. It’s just a steaming crater.

Yep. Manhattan, gone. The Statue Liberty, gone.

Hmm wow!

Very cinematographic though!

I mean, why hasn’t there been a film this? Wait, there was Deep Impact!

And Armageddon!

Wasn’t NY destroyed in Deep Impact?

Yeah, but not by an asteroid. In Armageddon, you have little bits of asteroids that somehow don’t burn the atmosphere and just go through buildings very precisely

Do they save the world in that one?

Yeah, they save the world and both of them.

But in one of them I’m sure there was like proper huge wave, there was someone sat on the edge of a cliff on a tsunami come towards them

She’s on the beach with her dad and they are having a moment. That’s Deep Impact. In Deep Impact, they split the comet in two so they have a tiny, itty bitty comet and then the other part. The Astronauts decided to just hit that other comet to save the world.

So it still impacted.

Parts of it. And destroyed part of the world.

Anyway, back to the death and destruction of New York. So that is a 50 to 80 meters asteroid. And I would say that is quite a likely asteroid.

So how would the people of New York have escaped this? How? Going back to the original question? Would it be possible for them to survive?

Yes. The idea is scanning the sky and that’s what NASA, ESA, and other space agencies are doing. There’s the fact that it requires money, it requires political commitment. And we have very little of that. It’s not a secret that politicians just care about the four or five years they’re in power. Otherwise, we would have a solution to climate change right now. And there are initiatives like asteroid day, which is on June 30, about how to raise awareness of the danger of asteroid impacts.

The reason why NASA and our federal agency are doing this [exercise] is to have a framework on how to evacuate people. And there is this big, big discussion on how are you going to convince people to just leave their homes and their possessions and everything, there’s going to be so many people that…

They just don’t want to go! Do you reckon that would be because it’s their home, it’s their everything and they don’t want to leave it or out of disbelief?

Probably both. In the previous simulation that was set on the West Coast, it was going to hit L.A. they said that one of the challenges was to make sure that the message would come across loud and clear. You know… fake news.

I mean, yeah, especially in today’s climate, you can just imagine being a backlash of “ugh, experts…”

Yeah, exactly. But also, it’s very, very difficult to ask people to just give up, give up everything, without knowing if they’re gonna have the means to survive. We’re gonna move the millions of people that live in New York, the jobs, etc. And in this scenario, they actually brought in a lawyer because technically NASA had pushed the asteroid from Denver to New York..

So the people of NY could sue the people of Denver?

No, they could sue the US government for endangerment.

Did they win?

No, they didn’t play the exercise that far. But it was a point that they raised. And this very much feels a good point in terms of the responsibility of governments to put in place disaster relief, but also disaster mitigation before they even happen. One of the things that were destroyed a few years back was the French Riviera. Obviously, they only pick fancy places with lots of rich white folk to make it more relevant to us. But obviously, if you’re hitting the south of France, you’re hitting Italy, you’re hitting Spain, you’re shaking about the Mediterranean. Is there going to be international efforts for mitigation? And what are we going to do? We already are quite terrible at helping migrants. If there is no framework for helping people to actual real welfare, we are going to be in a terrible position when, and it is when, this actually happens.

Okay. So you’re saying yes, it’s hypothetically possible that we could survive an asteroid impact. If it was to land in the sea, it would cause giant tsunamis. People and coastal regions would be the most at threat.

If it was going to crash into the land, there would likely either be people not believing that it was going to crash, we would have the difficulties of them not believing it was going to crash. You would have people wanting to stay and not give everything up. You would have people leaving, but the cost of giving up everything, but then with the added bonus that they could actually try and sue the government and all of that with an immense amount of disaster refugees.

Yes. And there’s also something else to consider that we didn’t touch. If a very big asteroid hit land, it would release so much dust and particles in the atmosphere and that might lead to a Global Winter.

Winter is coming!

Winter is coming and that is the most likely way for humanity to be wiped out from an asteroid impact. It is the inability to produce food. But then you also think how many places we have indoor or underground designed to grow food.

Like hydroponics places! There’s places like that in London.

Yes, there are hydroponics in abandoned World War Two shelters in London. So life can continue. How will it continue? It’s complicated when we don’t have the international cooperation and interest in the welfare of all humanity that you would need to fight off a global threat. But we’re seeing this with the climate crisis. So I feel that the asteroid should be slightly lower on our list of worries.

Okay, awesome. I hope that’s answered your sister’s question.

Well, she’ll let me know if I haven’t..!

Do you have any burning questions for the Astroholic? If so send them into me out @illucifer on Twitter, and I will spring it on him in an upcoming episode. See you next time!

Image credit: OSIRIS clear filter image taken during the flyby of the Rosetta spacecraft at asteroid Lutetia on July 10, 2010. ESA 2010 MPS/OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA