[According to most space scientists, our solar system went through a very violent formative phase during which many large objects collided with each other. Some of those collisions may have been enormously powerful. One of them possibly created the asteroid belt, for example, and another -- if new calculations are true -- fractured the early earth, creating both our present earth and our present moon. CNI News notes that this theory sounds similar to one put forth more than fifteen years ago by author Zecharia Sitchin in his book, "The Twelfth Planet." The following story was written by Robert S. Boyd for Knight-Ridder Newspapers. CNI News thanks Stig Agermose for forwarding this story to us.]
CAMBRIDGE, Mass. -- Astronomers have come up with a new answer to an age-old question: Where did the moon come from?
They now suspect that a wandering planet three times bigger than Mars sideswiped the Earth 4.5 billion years ago, destroying itself but blasting enough matter into space to form our lunar companion.
Until recently, the moon was believed to have been formed independently by the slow buildup of particles of gas and dust until it reached its present size and was captured by Earth's gravity.
If the new theory is correct, the moon that has inspired lovers, poets and myth-makers throughout human history is the result of a massive traffic accident in space -- a much more dramatic birth than the conventional view. And similar collisions could explain a lot about how the solar system was shaped.
According to Robin Canup, an astrophysicist at the University of Colorado, the heat created by such a tremendous collision would have vaporized much of Earth's crust, which was then just forming.
The fiery material spread into a gaseous disk spinning around the Earth, she suggested. The disk then broke apart into a handful of extremely hot "moonlets" which eventually coalesced into today's single large moon.
The "giant impact theory" is based on computer simulations performed by Canup and colleagues at Colorado's Laboratory for Atmospheric and Space Physics. Canup's paper was made available in advance of her scheduled presentation here Thursday [July 31] at a meeting of 600 planetary scientists, sponsored by the American Astronomical Society.
The notion that two planet-size objects banged into each other to form the moon was first proposed by Harvard University researchers 10 years ago. They suggested that the "impactor" was about the size of Mars, or twice the size of the moon. But such an object would not have the energy to produce enough material to form the moon, so doubts remained.
The new computer simulations have strengthened the impact theory, but indicate that the planet would have to have been much bigger -- 2.5 to three times the size of Mars.
According to Canup, the lost planet was probably orbiting the sun somewhere between the Earth and Mars when it got too close to Earth and smashed into it at an oblique angle.
Canup said similar massive impacts may explain such puzzles as the unusually large metal core of Mercury, the way Uranus tilts its north and south poles toward the sun, and the peculiar "double-planet" system composed of Pluto and Charon, a satellite half as big as Pluto.
[Story posted August 1, 1997.]
Original file name: CNI - Moon.Collision?
This file was converted with TextToHTML - (c) Logic n.v.