The Chicxulub asteroid was the ~7 mile wide asteroid which hit the Earth 65 million years ago and is thought to have brought about the destruction of the dinosaurs. It hit off the coast of Mexico and created a crater 110 miles in diameter. In all the documentaries I’ve seen about the event, it shows the asteroid landing straight down on the surface. But what if it instead had made more of a glancing blow along the side of the Earth? Would it have cut a huge gouge in the side as it plowed through the ground? What would happen to all the dirt that would have gotten flung into the air? In the documentaries they show most of the matter going up and down. But if it was a glancing blow, would all that matter be flung into space and eventually orbit the Earth?
(I hope it’s clear what I’m asking. To visualize, imagine a clock face projected over the Earth. Rather than the asteroid hitting the center of the clock, it hits as a glancing blow where the 3 or 9 is.)
NOVA just did a show on this a few weeks ago, and one thing that was mentioned is that if it had been just a few seconds* earlier or later, it would have landed completely in water and not done nearly as much harm. We are lucky!
*maybe it was a few minutes or even an hour or so.
Well at 7 miles wide, it isn’t large enough compared to the size of the earth to “leave a gouge”. My brief survey of related websites leads me to believe the impact was around 25degrees so it wasn’t a direct hit either way.
A truly glancing blow would have had it skipping off the atmosphere.
I saw that too. It was a great episode and got me wondering about this. Let’s say it still landed in basically the same place, but it’s trajectory was different. Let’s say it first impacted on the west coast of Mexico and traveled more horizontally towards the east coast. So rather than being on a trajectory towards the center of the Earth, it was more along the surface. Would it have been able to create a canal between the Gulf of Mexico and the Pacific?
So is it just the nature of asteroids, gravity, etc that an asteroid like that can’t really hit the Earth such that it would plow along the surface? Is it pretty much just going hit down into the surface or else skip off the atmosphere? Would it ever hit more or less like this Superman’s craft did in the movie where it madea gouge.
We’re used to low-speed impacts, where damage is done by one object pushing around pieces of the other object. But with high-speed impacts, it’s all about the energy, and nothing else matters. No matter the angle of impact, the energy is the same, and so the effects would be the same.
Earth has an atmosphere 62 miles thick (the edge is fuzzy, but this is a useful approximation for the extent) and the shallower the angle the more atmosphere the asteroid would have to pass through. This makes the real answer to your answer pretty complicated, I imagine.
Now I’m only a high school physics teacher, but my guess would be that the dinosaur-killer asteroid couldn’t have made a glancing blow of the kind you describe. If the angle is that shallow it instead deposits more energy in the atmosphere and either explodes before impact or impacts at much lower speed. And remember, for any ejecta to reach space they have to get through all that atmosphere going to other way, so if they didn’t make it from the face-on impact, they’re not getting there from a glancing blow either.
It is going to be picking up 7 miles per second in the directly towards the center of the earth direction before it hits, so it is going to have considerable vertical motion, no matter how much horizontal.
It left a crater about 20 miles deep. The ocean would be little more than a splash pool.
See this post from a couple of days ago. An asteroid (or comet) strike isn’t like tossing a marble into a sandbox where the angle that it hits makes a difference in the type of depression left–it is like throwing a hand grenade into a sandbox. The huge hole from the explosion obliterates any momentary hole from the size/direction of the impactor except in very low-angle hits. (There are a handful of elongated craters on some bodies in the solar system from those types of hits.)
A very shallow hit on the Earth would mean that it traces a much longer path through the atmosphere than a high-angle hit. It would dump massive amounts of heat into the atmosphere in the form of air being compressed ahead of the asteroid–enough heat to kill everything within a number of miles of the entry pant (tens? hundreds? I don’t know off the cuff), not to mention having your insides liquefied by the pressure wave. If the blow was (vanishingly improbably) glancing enough to touch the surface but not explode into a giant crater, it would dig a narrow groove and skip back off into space, doing the same sort of atmospheric damage on the way out as it did on the way in. Thousands of square miles would be more or less sterilized, but the world as a whole would likely recover fairly quickly.
Wouldn’t the situation you describe in the 2nd paragraph be more likely to cause an air burst (not sure if that’s the right word… I’m talking about the object exploding in the atmosphere prior to impact.) similar to Tunguska?
A small (maybe 200 to 600 feet) meteoroid like Tunguska can be shattered by the stresses of the Earth’s atmosphere. An asteroid the size of Chicxulub would cut through the atmosphere like a lightsaber through cotton candy.
The only “happy path” through a Chicxulub encounter is where is misses all, or almost all, of the atmosphere.
Viewed from space, the cross-section of the solid Earth + atmosphere is about 3% larger than the cross-section of the solid Earth. So about 97% of meteors that touch the atmosphere will also touch the surface. And about 99% of meteors that touch the atmosphere will touch either the surface or the deep atmosphere enough to trigger Darren’s damage descriptions just above.
When it comes to meteors, pretty much we can assume it’s either a clean miss or a thorough hit; there’s very little margin between them. This will be true whether the meteor is the size of a grain of sand or a mountain or an island. Obviously the damage from a direct hit by a sand grain is negligible, unlike the larger options.
ISTR seeing a documentary where it was demonstrated that the angle of impact didn’t change the shape of the crater. IIRC, they used some sort of gigantic air cannon to launch pellets. (This was an actual research facility, not Mythbusters.)
As noted, basically it comes down to energy. To change how much energy was involved requires the “glancing blow” to take some energy away in some other form.
Basically this means that a good size piece of the asteroid somehow continues off into space after the blow. Maybe it just grazed the atmosphere, never actually hitting the ground, etc.
A lot of heat, dust, etc. still ensues. The effects ranging from quite significant to really huge depending on how much energy and material is expended in the atmosphere.
But the bad news is that there’s still a big piece of rock in an orbit that intersects Earth’s and it’s likely to do a full hit later. (Or it might hit the Moon, Venus, etc. at some later point.)
Even the “a little bit sooner or later and it would have missed” isn’t really such great news. It’s still out there and it’s going to hit something.
Also, Chicxulub is thought to have struck in an especially bad spot with lots of sulfate deposits that were injected into the atmosphere, and life may have already been under strain by the volcanic eruptions from the Deccan traps. If the impact had been in a different spot or a different time (if the Deccan traps are a factor) then the extinctions might not have been so bad. There have been several pretty big whacks that haven’t caused as much extinction as Chicxulub.
Just a point of clarification: there is no such thing as “skipping off the atmosphere” in the sense that a flat stone can skip off water. The atmosphere won’t redirect a 7km asteroid (or a 7m meteoroid for that matter) in any significant way.
The idea of skipping off the atmosphere, so far as I can tell, comes from descriptions of re-entry of the Apollo Command Module at perigee of its translunar return orbit. Pretty sure there’s a scene in Apollo 13 to that effect. But the spacecraft wouldn’t have been “skipping off” the atmosphere in any significant respect - the atmosphere wouldn’t have been deflecting it outward into space. The capsule was already on a trajectory that took it back into space, i.e. an elliptical orbit with a perigee slightly inside the earth’s atmosphere. By “coming in too shallow” they wouldn’t “skip off the atmosphere” like a stone off of water. Rather, they simply wouldn’t aero-brake enough to drop their apogee into the atmosphere, and would swing out for another orbit. In the case of an Apollo mission, this would have been a death sentence for the astronauts as their life support was jettisoned before re-entry, so it was certainly important to get it right, but the result would simply have been another re-entry on the next orbit, and sooner or later it would have aero-braked sufficiently to de-orbit.
An asteroid, on the other hand, is on a hyperbolic rather than elliptical orbit. If it passes through the atmosphere and back out again without hitting the surface, this isn’t so much “skipping off the atmosphere” as it is simply missing the planet. To the extent that aerodynamic forces will affect the asteroid’s trajectory they will actually bring it closer to the surface, by slowing it down and giving Earth’s gravity more time to tug at it.
