Is it possible for meteors to become trapped in Earth’s orbit? If so, why isn’t Earth’s upper atmosphere choked with a billion years of accumulated space rocks?
In: Physics
It’s just so unlikely for all the factors to line up perfectly for it to happen, and then stay there. The object’s speed, direction of travel, distance, etc would all have to be perfect. It would also be competing with the moon, which is a major factor.
Edit – removed article that I linked about a small object in THE SAME orbit as Earth’s (not orbiting earth) and misremembered what I had read when I used it as a source.
The atmosphere would create atmospheric drag slowing down objects so that gravity would take over and they fall to Earth, further out there are temporarily captured objects or mini-Moons, but they too don’ last long.
It’s not impossibe, but it’s unlikely to happen nowadays.
In space there’s no (significant) loss of energy (we’ll ignore tidal forces). Everything has an amount of gravitational potential and kinetic energy relative to everything else. Something that is pulled towards Earth accelerates as it gets closer, turning that gravitational energy to potential energy. Once it’s at the closest point, the object has the same energy still; less gravitational energy, but more kinetic energy (velocity) so will fly off just as far as where it came from. This means with two bodies, there can’t be a change from not orbiting to orbiting. Either the objects came into existence orbiting, they crashed into eachother or they are doomed to fly apart forever.
So if there’s no loss of energy, the only way for something to become trapped in orbit is by transfer of energy. When you have two bodies orbiting a larger body (the sun), then when the two bodies pass by each other from specific directions, it’s possible for some kinetic energy to pass from one body to the other, accelerating one body and decelerating the other. The thing is:
1. There’s a limit as to how much energy can be transferred like this in a single pass
2. Slowing something down requires approaching from a particular direction.
This means the only objects that can realistically be captured by the Earth’s gravity had to start life on a similar orbit to Earth. Most of those have already been captured in orbit – or crashed in to Earth.
Yes, it is possible.
In fact there are countless numbers of incredibly tiny asteroids in a small areas called the [Kordylewski cloud](https://en.wikipedia.org/wiki/Kordylewski_cloud).
But as for why they aren’t in the upper atmosphere, if they were the atmosphere would slow down the asteroid until it crashed into earth and became part of earth.
This is pretty much how the earth was formed.
Just lots and lots of asteroids getting too close and crashing and building up.
As for why there aren’t any big asteroids.
The earth is going around the sun.
The moon is going around the earth.
This means that the gravity fields are going all over the place and there isn’t much of a safe zone for things to end up in.
Either it crashes into the earth or moon or sun, or just get flung out elsewhere.
The Kordylewski cloud are located where the gravity fields of the earth and moon sorta cancel out. These places are called LaGrange points. But the odds of something getting there at just the right speed are so low that only tiny asteroids have hit those long odds.
Big planets like Jupiter are so large that they have enough gravity so there’s actually big stuff in some of their LaGrange points.
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