On 1994 July 16-22, over twenty fragments of comet Shoemaker-Levy 9 collided with the planet Jupiter. Before that time, even though there was ample evidence, direct observation of an impact between object in our Solar System had no solid proofs. Now it's commonly accepted that comets have and will continue to fall on their heavenly neighbors. Collisions between even more massive object was accepted as statistically unlikely and had not been observed in astronomical history. That was until a big rock called 2003 EL61, which is almost the size of Pluto, was discovered. In the
Kuiper Belt where most object are made up of ice, resides El61, an extremely large rocky body. Not only is this huge rocky object there, it is the
only object in our solar system shaped like an American football and tumbling long end-over-end every four hours, making it one of the fastest spinning object in our Solar System. Planetary astronomer Michael Brown, Ph.D., at Cal Tech, says he has discovered icy satellites in the EL61 region that have surface properties nearly identical to those of 2003 EL61. These satellites suggest a gigantic impact long ago. Brown thinks that EL61 was once covered in ice and as large as Pluto. Some time ago EL61 was struck a glancing blow at extremely high speed, by another rocky body, maybe as much as 60% of EL61's mass. This type of collision would have blown off the outer ice mantle and sped up the rotation. The spin itself would have pulled it out into the shape like the football. It is just such a collision with a Mars sized planet that might have been responsible for splitting of a major piece of crust and forming Earth's
satellite - the Moon
