You are talking here about an asteroid of the order of several hundred or thousand kilometers in diameter. Vesta or Ceres perhaps? Or the Moon? You want an impact that boils the oceans away all the way down to the ocean depths, and makes the entire surface of the Earth molten down to a depth of many kilometers.
We have life deep in the oceans (where the creatures in hydrothermal vents can withstand high temperatures above boiling point already), and many kilometers underground. Even eleven kilometers below the ocean floor. That's deep: life found 11km below sea level in deepest known point on the surface of the Earth
So even impacts that bring the surface of the oceans to boiling point would be easily survivable by these lifeforms.
The Earth's oceans have a volume of 1,335,000,000 cu km see Volumes of the World's Oceans from ETOPO1 . Volume of Ceres is 452,331,448 cu km. Ceres: Overview. So to boil the Earth's oceans you'd need to boil the equivalent of nearly three times the volume of Ceres. And that's not enough because you also have to melt the Earth's crust down to a depth of many kilometers.
The impact that brought an end to the dinosaur era wouldn't even kill all humans. After all, many mammals survived it (that's why we are here).
Without any technology, little creatures perhaps living in burrows were able to survive. Birds also survived it, perhaps by flying out to sea. Crocodiles survived it, and both river and sea turtles.
So of course many humans would. E.g. people in Antarctica, or climbing snowy mountains with nothing to burn in a global firestorm. Or under the sea in a submarine. Out at sea in a boat, if far from the impact site.
And in any case we'd see it coming for at least months before - something that size, and could build fire shelters etc, build up stocks of food and so on.
(And within a few decades, perhaps even by late 2020s, we will have nearly all near Earth asteroids mapped, and then chance we are surprised goes way down - and if we see anything headed our way, we can get started on deflecting it decades before it hits Earth).
As for Vesta and Ceres sized asteroid- we no longer get asteroids that big in the inner solar system. You are talking about an impactor many times larger than the moons of Mars which amateurs can see from Earth. We'd see it from way across the solar system.
We could get surprised by a huge comet from the Oort cloud or the Kuiper belt with at most a year or so of notice. But - those come from random directions with random inclinations very unlikely to lie in the same plane as the Earth's orbit. Like Halley's orbit. Technically it's an "Earth crosser" but it's orbit can never take it anywhere close to Earth as you can see in this video:
So - most comets are like that. Chance that a new comet coming into the inner solar system is even on an orbit that intersects with the Earth's orbit is minute. And Earth is a tiny target on its orbit around the sun.
So before they become a threat then they need to get their orbits flattened down into the same plane as the Earth, e.g. through influence of Jupiter and repeated flybys of Jupiter. But that also tends to break them apart through tidal effects.
We can see that also from the meteorite crater record of the solar system. There are no huge craters in the inner solar system younger than 3 billion years.
The Moon, Mercury, and Mars all have huge craters from the late heavy bombardment between 3.8 and 3.5 billion years ago.
the
Earth surely had impacts this large back then as well, but the evidence is probably long erased. For the largest I can find, see this Impact of 23-mile-wide asteroid boiled Earth's oceans 3.26 billion years ago (and another link, and scientific paper). When it says it boiled the oceans there - doesn't mean it boiled them dry, just surface layers, and it would come nowhere near making all life extinct.
(Venus doesn't have these craters, because it's surface is relatively young, whole planet gets resurfaced every few hundred million years because it has no continental drift and instead from time to time the entire surface "flips"). But nothing large since then.
So the inner solar system is pretty much cleared out of objects like that. What's left are in stable orbits at least for hundreds of millions of years - the likes of Mercury, Vesta and Ceres.
And anything from the outer solar system has to get past Jupiter, which tends to catch the really big ones or break them up.
More accurately - anything close to the plane of the solar system, if it is in a Jupiter crossing orbit, is likely to do a close flyby of Jupiter first, because Jupiter's gravitational influence is so large.
Jupiter's Hill radius - sphere of influence - is 53 million km and its distance from the sun is 778 million kilometers.
Earth's hill radius is about 1.5 million km (1,497,000) and its distance from the sun is about 150 million km (149,600,000 km) - ratio of the two is actually larger, but of course, Earth's gravitational influence is much less on anything that passes through its Hill sphere.
File:Hill sphere of the planets.png (log plot)
Also:
Hill Sphere calculator
Also
Planetary Calculator framed home page
lets you find the Hill spheres of all the planets in one go.
So - in a single flyby it's likely to miss Jupiter but almost no chance of hitting the tiny Earth as we see from the cratering record. With repeated flybys, unless it gets into some resonance with Jupiter, it's going to encounter Jupiter pretty soon.
I wouldn't lose any sleep over this possibility :). But smaller dinosaur extinction ones - they are worth tracking and searching for. 1 in a million chance, roughly, per century, of getting hit by one of them.
And more so - the smaller ones like at most hundreds of meters diameter. They are well worth tracking, and also, not that hard to deflect. And since they are much more numerous, then far more likely to be hit by one of those.
Though not even civilization threatening, they could be devastating in the same way that a tsunami is or a major earthquake. So - well worth searching for them and protecting against them. If we do need to deflect an asteroid any time in the near future - I would expect it to be much more likely to be, say 50 to 100 meters asteroid, than a 1 km to 10 km one. Just because they are far more common.
We have life deep in the oceans (where the creatures in hydrothermal vents can withstand high temperatures above boiling point already), and many kilometers underground. Even eleven kilometers below the ocean floor. That's deep: life found 11km below sea level in deepest known point on the surface of the Earth
So even impacts that bring the surface of the oceans to boiling point would be easily survivable by these lifeforms.
The Earth's oceans have a volume of 1,335,000,000 cu km see Volumes of the World's Oceans from ETOPO1 . Volume of Ceres is 452,331,448 cu km. Ceres: Overview. So to boil the Earth's oceans you'd need to boil the equivalent of nearly three times the volume of Ceres. And that's not enough because you also have to melt the Earth's crust down to a depth of many kilometers.
The impact that brought an end to the dinosaur era wouldn't even kill all humans. After all, many mammals survived it (that's why we are here).
Without any technology, little creatures perhaps living in burrows were able to survive. Birds also survived it, perhaps by flying out to sea. Crocodiles survived it, and both river and sea turtles.
River turtle, Boremys basking on a Triceratops dinosaur skull, Credit: Brian T. Roach, Yale Peabody Museum
How Tough Turtles Survived Dino-Killing Meteor
So of course many humans would. E.g. people in Antarctica, or climbing snowy mountains with nothing to burn in a global firestorm. Or under the sea in a submarine. Out at sea in a boat, if far from the impact site.
And in any case we'd see it coming for at least months before - something that size, and could build fire shelters etc, build up stocks of food and so on.
(And within a few decades, perhaps even by late 2020s, we will have nearly all near Earth asteroids mapped, and then chance we are surprised goes way down - and if we see anything headed our way, we can get started on deflecting it decades before it hits Earth).
As for Vesta and Ceres sized asteroid- we no longer get asteroids that big in the inner solar system. You are talking about an impactor many times larger than the moons of Mars which amateurs can see from Earth. We'd see it from way across the solar system.
We could get surprised by a huge comet from the Oort cloud or the Kuiper belt with at most a year or so of notice. But - those come from random directions with random inclinations very unlikely to lie in the same plane as the Earth's orbit. Like Halley's orbit. Technically it's an "Earth crosser" but it's orbit can never take it anywhere close to Earth as you can see in this video:
So - most comets are like that. Chance that a new comet coming into the inner solar system is even on an orbit that intersects with the Earth's orbit is minute. And Earth is a tiny target on its orbit around the sun.
So before they become a threat then they need to get their orbits flattened down into the same plane as the Earth, e.g. through influence of Jupiter and repeated flybys of Jupiter. But that also tends to break them apart through tidal effects.
We can see that also from the meteorite crater record of the solar system. There are no huge craters in the inner solar system younger than 3 billion years.
The Moon, Mercury, and Mars all have huge craters from the late heavy bombardment between 3.8 and 3.5 billion years ago.
the
Impact from 3.8 billion years ago when large asteroid impacts were still common. 3D map of Mars - Hellas Basin on Mars
The Aitken basin at the lunar South pole. It's believed to be over 3.8 billion years but the exact date is hard to pin down. Impact of an asteroid perhaps 170 km in diameter.
The Caloris basin on Mercury.
Earth surely had impacts this large back then as well, but the evidence is probably long erased. For the largest I can find, see this Impact of 23-mile-wide asteroid boiled Earth's oceans 3.26 billion years ago (and another link, and scientific paper). When it says it boiled the oceans there - doesn't mean it boiled them dry, just surface layers, and it would come nowhere near making all life extinct.
(Venus doesn't have these craters, because it's surface is relatively young, whole planet gets resurfaced every few hundred million years because it has no continental drift and instead from time to time the entire surface "flips"). But nothing large since then.
So the inner solar system is pretty much cleared out of objects like that. What's left are in stable orbits at least for hundreds of millions of years - the likes of Mercury, Vesta and Ceres.
And anything from the outer solar system has to get past Jupiter, which tends to catch the really big ones or break them up.
More accurately - anything close to the plane of the solar system, if it is in a Jupiter crossing orbit, is likely to do a close flyby of Jupiter first, because Jupiter's gravitational influence is so large.
Jupiter's Hill radius - sphere of influence - is 53 million km and its distance from the sun is 778 million kilometers.
Earth's hill radius is about 1.5 million km (1,497,000) and its distance from the sun is about 150 million km (149,600,000 km) - ratio of the two is actually larger, but of course, Earth's gravitational influence is much less on anything that passes through its Hill sphere.
Also:
Hill Sphere calculator
Also
Planetary Calculator framed home page
lets you find the Hill spheres of all the planets in one go.
So - in a single flyby it's likely to miss Jupiter but almost no chance of hitting the tiny Earth as we see from the cratering record. With repeated flybys, unless it gets into some resonance with Jupiter, it's going to encounter Jupiter pretty soon.
I wouldn't lose any sleep over this possibility :). But smaller dinosaur extinction ones - they are worth tracking and searching for. 1 in a million chance, roughly, per century, of getting hit by one of them.
And more so - the smaller ones like at most hundreds of meters diameter. They are well worth tracking, and also, not that hard to deflect. And since they are much more numerous, then far more likely to be hit by one of those.
Though not even civilization threatening, they could be devastating in the same way that a tsunami is or a major earthquake. So - well worth searching for them and protecting against them. If we do need to deflect an asteroid any time in the near future - I would expect it to be much more likely to be, say 50 to 100 meters asteroid, than a 1 km to 10 km one. Just because they are far more common.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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