Wrongway Moon

[Dragonrock]

I thought about this after reading about the moon running away from the earth.

The moon is orbiting the earth in the same direction as the earth's rotation. Because of this the earth is imparting some of its rotational energy into the moon causing the moon's orbit to increase very slowly. Now, suppose there was an earthlike planet that did not have a moon and a large asteroid were somehow moving by that planet at just the right speed and happened to get caught in a stable, circular, equatorial orbit in the opposite direction of planetary rotation.

My question is, would that orbit be stable enough to last billions of years and would it have any effects on said planet that would prevent the development of intelligent life? Assuming that, would the transfer of rotational energy gradually slow the moon until it fell from orbit?

 

[roger]

triton orbits Neptune the "wrong" way.

 

[Dragonrock]

triton orbits Neptune the "wrong" way.

True, but I doubt neptune transfers much energy due to the lack of liquid on it surface.

 

[Larspeart]

Dragon, your statement is wrong for a few reasons. Neptune doesn't really have a 'surface. much like Jupiter and Saturn, it is a gas planet.

Secondly, most scientists believe now that Neptune has a liquid layer, or a liquid core. Methane is the likely liquid.

Methane would work in the same manner as water would on the pull on Triton.

 

[CurtC]

IANARS, but I think that its orbit would get lower and lower until either one of two things happened: 1) its orbit fell within the distance that a Moon could be before the Earth's tidal forces pulled it apart, or 2) the Earth's rotation would gradually reverse and lock up to that of the Moon, at which point the system stabilizes. Either of these would take a really long time to occur.

 

[ceptimus]

An asteroid can't get trapped in a circular orbit like that, but lets just assume it's there.

1. Unless it is massive enough to raise appreciable tides on the Earth, there wouldn't be much interaction.

2. If it did raise tides, the Earths's rotation would be slowed down (as it is by our present moon) and the asteroid would gradually spiral in closer.

3. It might get broken up by tidal forces before it hit the Earth, and then we would get a set of rings, like Saturn.

Unless and until it got close enough to create massive tides, I don't think the opposite rotation would make much difference. For every once our moon goes round, the earth spins about 29 times. If the moon went round the other way, it's apparent motion in the sky would only be about 7% faster.

 

[Dragonrock]

Dragon, your statement is wrong for a few reasons. Neptune doesn't really have a 'surface. much like Jupiter and Saturn, it is a gas planet.

Secondly, most scientists believe now that Neptune has a liquid layer, or a liquid core. Methane is the likely liquid.

Methane would work in the same manner as water would on the pull on Triton.

I had a brain fart, I was thinking that Neptune was frozen solid. But, back to my original question, would a moon like I mentioned last for billions of years then crash into the planet?

 

[Dragonrock]

An asteroid can't get trapped in a circular orbit like that, but lets just assume it's there.

1. Unless it is massive enough to raise appreciable tides on the Earth, there wouldn't be much interaction.

2. If it did raise tides, the Earths's rotation would be slowed down (as it is by our present moon) and the asteroid would gradually spiral in closer.

3. It might get broken up by tidal forces before it hit the Earth, and then we would get a set of rings, like Saturn.

Unless and until it got close enough to create massive tides, I don't think the opposite rotation would make much difference. For every once our moon goes round, the earth spins about 29 times. If the moon went round the other way, it's apparent motion in the sky would only be about 7% faster.

The reason I was asking this is I had a story in mind. My thinking was that it would eventually crash into the planet and any astronomers on the planet would be able to predict when it would happen with a fair degree of accuracy. Because of this, if there were people on that planet then they would have a doomsday feeling unlike anything we have on earth. They know the end is nigh, and if their species was to survive they would have to plan on going off world. A great big ticking time bomb that could never be disarmed.

 

[Andonyx]

An asteroid can't get trapped in a circular orbit like that, but lets just assume it's there.

Hmm, would it form an elliptical orbit or am I on the wrong track here?

 

[Diamond]

In about a billion years, Triton will break up into tiny fragments and the solar system will have another beautiful ringed planet again (Saturn having lost its rings 800-900 million years previously)

 

[CurtC]

Andonyx, in order to get into orbit, it would have to get rid of some of its speed (energy). If it hit something else, it possibly could, but it would likely be a very elliptical orbit.

For your story, could you instead just have a collision like what created or own moon, except with the debris sent out with opposite angular momentum? That way, when it coalesced into a moon, it would be going the opposite direction, and you could make it be a really long time after that before it would be pulled apart by tidal forces.