lpetrich
21 Mar 2009, 01:35 PM
According to this article (http://www.space.com/scienceastronomy/solarsystem/fifth_planet_020318.html) and this article (http://www.aas.org/publications/baas/v33n3/dps2001/505.htm), there is an interesting theory that can account for a curious phenomenon in the early history of the Solar System, the Late Heavy Bombardment.
That is a curious peak in the Moon's bombardment rate that had happened 3.9 billion years ago -- 600 million years after the Solar System's origin.
So what provoked the coming of that swarm of big rocks?
If they had been left over from the origin of the Solar System, one would expect their abundance to continually dwindle as they collide with other objects. There would not be anything to provoke them to start colliding with other objects all of a sudden.
But astronomers John Chambers and Jack Lissauer have proposed that there had once been a fifth terrestrial planet, one that had orbited a little beyond Mars's orbit. Being a little beyond make its orbit suffer dynamical chaos over timescales of a few million years ago, and after about 600 million years, it had a near-collision with Mars and got into a much more eccentric orbit whose aphelion extended into the Asteroid Belt.
This caused a lot of asteroids to be deflected into orbits which took them into the inner Solar System, where they proceeded to strike the Earth, the Moon, and Mars, with a few of them striking Mercury.
Thus producing the Moon's Late Heavy Bombardment.
And what happened to this planet afterwards? A likely fate is colliding with some other Solar-System object, most likely Venus or Jupiter.
Finally, I consider the question of what to call this object, if it had existed. I propose Eris, after the Greek goddess of discord, though Loki, after the Norse god of mischief, may also be a good one.
There is an additional Eris connection. According to the story, she was not invited to the wedding of Peleus and Thetis, so she took one of the Golden Apples of the Hesperides, wrote "For the fairest" on it, and threw it into the wedding party.
Hera, Athena, and Aphrodite bickered among themselves about who would get this title, and Zeus decided to settle it by having a shepherd named Paris decide. Hera offered him the rule of much of the known world, Athena offered him great military prowess, and Aphrodite the love of the most beautiful woman in the world, a certain Helen. Paris chose that love, but that pissed off Helen's family, causing the Trojan War.
So Eris might be a good name for a planet which once did some "throwing", also with devastating effects.
That is a curious peak in the Moon's bombardment rate that had happened 3.9 billion years ago -- 600 million years after the Solar System's origin.
So what provoked the coming of that swarm of big rocks?
If they had been left over from the origin of the Solar System, one would expect their abundance to continually dwindle as they collide with other objects. There would not be anything to provoke them to start colliding with other objects all of a sudden.
But astronomers John Chambers and Jack Lissauer have proposed that there had once been a fifth terrestrial planet, one that had orbited a little beyond Mars's orbit. Being a little beyond make its orbit suffer dynamical chaos over timescales of a few million years ago, and after about 600 million years, it had a near-collision with Mars and got into a much more eccentric orbit whose aphelion extended into the Asteroid Belt.
This caused a lot of asteroids to be deflected into orbits which took them into the inner Solar System, where they proceeded to strike the Earth, the Moon, and Mars, with a few of them striking Mercury.
Thus producing the Moon's Late Heavy Bombardment.
And what happened to this planet afterwards? A likely fate is colliding with some other Solar-System object, most likely Venus or Jupiter.
Finally, I consider the question of what to call this object, if it had existed. I propose Eris, after the Greek goddess of discord, though Loki, after the Norse god of mischief, may also be a good one.
There is an additional Eris connection. According to the story, she was not invited to the wedding of Peleus and Thetis, so she took one of the Golden Apples of the Hesperides, wrote "For the fairest" on it, and threw it into the wedding party.
Hera, Athena, and Aphrodite bickered among themselves about who would get this title, and Zeus decided to settle it by having a shepherd named Paris decide. Hera offered him the rule of much of the known world, Athena offered him great military prowess, and Aphrodite the love of the most beautiful woman in the world, a certain Helen. Paris chose that love, but that pissed off Helen's family, causing the Trojan War.
So Eris might be a good name for a planet which once did some "throwing", also with devastating effects.