Could the Earth capture an Asteroid?

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Offline GlentoranMark

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Could the Earth capture an Asteroid?
« on: 03/01/2010 02:44:58 »
There's a lot of recent information about Near Earth Asteroids and there seems to be a lot out there but could the Earth capture one? And is there any possible candidates?

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Offline LeeE

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Could the Earth capture an Asteroid?
« Reply #1 on: 03/01/2010 12:28:14 »
I think it's extremely unlikely that the Earth would capture an asteroid.

First of all, the asteroid would need to have an aphelion very close to the Earth's orbit, and then it would need to be at aphelion when it coincided with the Earth's position around its orbit.  Even then, the chances are far greater that the asteroid would collide with the Earth, or be perturbed from its path than captured.

None of the known NE asteroids are candidates for capture as their aphelions are either inside the Earth's orbit and don't come close enough for capture, or are outside the Earth's orbit and are travelling too fast for capture.  The fact that there are no NE asteroids with an aphelion  very close to Earth's orbit indicates that any that were have either collided or been perturbed into different orbits.

Any asteroids that could be captured then, would have to be 'new' ones, entering the inner solar system for the first time, and which would need to be slowed, possibly as a result of multiple perturbations by the inner planets, such that it ended up in orbit about the Sun with its aphelion at the Earth's orbit.  Once that orbit was established, it would just be a matter of (relatively short) time before it either collided with the Earth, was perturbed into a new orbit, or in the least likely event, captured.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline RD

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« Last Edit: 03/01/2010 13:35:59 by RD »

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Offline GlentoranMark

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Could the Earth capture an Asteroid?
« Reply #3 on: 03/01/2010 15:17:04 »
Surely a NEA could be deflected into a stable orbit? It must have happened in the past and I'm sure it will happen in the future. I was reading about Phobos, it will eventually spiral into Mars and very possibly form a ring system around the planet. I wonder did the Earth ever have a ring? They are pretty common amongst the larger planets in the Solar System.

Thanks for the link on Cruithne, that's the reason I love this site, learn something new every day.

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Offline LeeE

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Could the Earth capture an Asteroid?
« Reply #4 on: 03/01/2010 21:35:08 »
Heh  [;D], but Cruithne is probably even less likely than Earth capturing an asteroid.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline RD

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Could the Earth capture an Asteroid?
« Reply #5 on: 03/01/2010 23:08:56 »
The asteroid 2002 AA29 orbits Earth, sort of, (or at least the Germans think so) ...

[attachment=11006]

http://en.wikipedia.org/wiki/File:2002aa29-orbit-4.png

http://en.wikipedia.org/wiki/2002_AA29

[BTW I've thought of a rhyme for Cruithne (see youtube link above)
"I won't be seein' ya, I'm going to Cruithne"  [:)] ]
« Last Edit: 03/01/2010 23:22:33 by RD »

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Offline LeeE

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Could the Earth capture an Asteroid?
« Reply #6 on: 04/01/2010 10:54:50 »
I hadn't come across 2002_AA29 before - it's a very interesting object - ta for posting the link.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!