At what relative velocity does an asteroid have to travel to be captured by a planet as a satellite?

Question

How close would it have to be? What about collisions, what makes an asteroid that is captured not collide, or does it eventually, like Phobos and Deimos will?

Answer 1

I think this maybe some of what you are looking for, I will continue to look.

http://www.astro.umd.edu/~cmcgleam/research.html
http://www.unmannedspaceflight.com/index.php?showtopic=1305
http://www.physorg.com/news66489496.html

Answer 2

The short answer is, "less than escape velocity".

The long answer is that escape velocity is different for different planets and different at different distances from those planets. Any asteroid will always be traveling faster than escape velocity as it passes any planet, because it started out "escaped" in the first place. And it will speed up as it approaches the planet in question, due to the planet's gravity pulling it in, so it is always going faster than escape velocity. The only way it could be captured is if it gets a gravity assist from a 3rd body; either another asteroid or a moon already circling the target planet.

Answer 3

It requires help from a third body. If an asteroid was not orbiting a planet before encountering it, it will have a hyperbolic orbit with respect to that planet, and no orbit can form. But if another body is around, its gravity can influence the orbit to become elliptical: capture takes place.

Answer 4

If the asteroid was the mass of the space shuttle, then it would need to be traveling between 17,000 and 18,000 mph and pass roughly 200-250 miles above the earth's surface.

That may give you some idea.

Answer 5

Read about Escape velocity. This will explain the trajectories of objects around gravitational objects.

Answer 6

Lots of variables involved here -- mass of asteroid, mass of planet, angle of approach, etc.,.

Answer 7

I think that asteroids will just melt away.