It’s currently calculated that the asteroid Apophis isn’t going to impact the Earth, but according to the Wiki page, if it were, it could impact in central America. Would such an impact there be big enough (880MT) to break the land bridge between the Americas? If so, would this affect the Gulf Stream?
A couple of things.
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My understanding is that it’s much more likely to impact in the pacific ocean off the coast of Mexico. Granted that the probabilities we’re talking about here are minuscule.
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The impact, should it happen, is supposed to release 3.2 EJ of energy. For comparison, the 1906 San Fransisco earthquake released about 4.2 EJ of energy. And the Chicxulub meteor impact released 500 ZJ (so 500,000 EJ) of energy. So I’d say no, that’s not enough to break the land bridge.
880 Megatons = 3.7 exajoules, not 3.2 exajoules. My bad.
Not even close. To breach the Isthmus in Panama, the narrowest point, you would need a crater more than 50 miles in diameter. Creating a breach that would permit fairly free flow of water would require a crater a good deal larger.
Manicouagan Crater, at a diameter of 62 miles, is in the right ballpark. According to the article, the asteriod that created it was 5 kilometers in diameter, thus more than 14 times larger in diameter than Apophis (350 meters). The mass difference of course will be proportionately much larger.
Even a crater the size of Manicouagan probably won’t allow enough water to flow between the oceans to affect the Gulf Stream much, since the narrowest part of the straight will be only a few kilometers across and it is likely to be shallow due to filling in with rubble.
On a related subject, the wiki article mentioned that it will pass within the orbit of geosynchronous satellites, but no one seems concerned that it will knock one or more of them out of orbit. I suppose it’s due to the fact that space is big (really, really big; no bigger than that), the asteroid is fairly small, and we can only vaguely estimate where it’s going to be at the time is comes near. But still, it’s possible; isn’t anyone concerned?
“Will someone not think of the geosynchronous satellites?!?”
The Wiki article also covered that: Although it’s going to be closer than geosynchronous orbit, it’s not actually going to intersect with geostationary orbits. Think of something passing through a hoop, not something crossing a boundary.
Though there are some satellites and space probes further out, the bulk of our satellites are going to be in geosynchronous or lower orbits–from about 22,000 miles out (for certain weather satellites and communications satellites) to only a few hundred miles up (for the International Space Station).
The geosynchronous orbits are at the outer edge of a sphere of space with a volume of over 40 trillion cubic miles. Even if you assumed that most of our satellites are going to be distributed in a flat disk on the plane of the Equator rather than being located willy-nilly throughout that sphere–and the fact is that satellites have been launched into many different orbits with all sorts of inclinations to the Earth’s equator, all the way up to completely perpendicular to it–you’re still talking about an area of over 6 billion square miles.
In other words, space really is just that damned big. The odds of a space rock hitting anything are low.
Interestingly, the International Space Station just had a near miss (less than a mile) with a piece of our own space junk; and earlier this year two of our satellites collided (a non-functional Russian satellite and a perfectly good Iridium communications satellite). We’re much more likely to screw ourselves up with our own debris than some rock whizzing in from elsewhere in the Solar System is–asteroids and meteoroids will probably just fly on through and out the other side, whereas our own satellites and old non-functioning satellites and pieces of satellites are all orbiting around together. The odds of a satellite or something that was used to launch a satellite having a similar orbit to somebody else’s satellite are much greater, since certain orbital spaces are inherently useful to humans, and because they’re all in orbit together, they can spend years zooming past each other over and over again until eventually they crash.
Even so, this year’s collision was a first, and we’ve sent thousands of things into orbit since 1957.
While I knew the probability of impact was minimal even if it would pass through the area that the geosynchronous satellites orbited, I failed to remember that all such orbits are by necessity directly over the equator. I had just thought “well, if it passes through the sphere of the right distance from the Earth, the probability it’ll hit such a satellite is non-zero.” If it passes really close it might hit some mid orbit satellites (like the GPS ones presumably are), but the lack of information in that regard makes it seem unlikely.
I suppose with all the debris up there a 300m rock just passing through is nothing to worry about.
The Stargate SG1 team will save us I am sure.