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Author Topic: Could Earth have coalesced from the collision of two smaller planets?  (Read 2497 times)

Offline Bill S

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A poster in another discussion forum argues that Earth formed as a result of the collision of two medium sized planets. 

The following is taken from the start of his O P.

"Heaven and PreEarth were planets, a binary system orbiting the Sun. This happy arrangement continued for countless years, until, some unfortunate circumstance caused Heaven to collide with PreEarth, forming the Earth.

We investigate the evidence that the Earth is the child of such a collision. We show that the planets Heaven and PreEarth were of similar size and mass. We show that many of the Earth's topographical features, such as mountain chains and ocean basins, were created during the collision. We show that certain hard to explain features of the Earth, such as its magnetic field, can now be more easily understood. And, in establishing all this, we uncover a new theory on the origin of the Moon.

Much of PreEarth's crust survived the impact and is today the continental crust of the Earth. Although broken and contorted, giant pieces of the ancient crust acted as ships floating on a newly molten interior, insulating, and protecting, life from the fires below. Heaven itself, together with its crust, if it had one, disappeared into the interior of the PreEarth, never to be seen again."

  I understand that he is not the first to propose this idea.  Is there any real scientific evidence for it?


 

Offline CliffordK

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There is a lot of information you'll find on the web about the Theia Giant Impact Hypothesis. 

In particular, it discusses the formation of the moon. 

It seems odd that very little physical evidence has been found on the earth.  I.E.  No obvious chimera of earth rocks and Theia rocks.

The main evidence is apparently the similarity between Earth Rocks and Moon Rocks.  This similarity excludes the possibility that the moon was a stray asteroid captured from the Earth.  But, rather it would have been formed from the same material from which the earth was formed, either from a deep impact, or from the same accretion material.
 

Offline RD

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... Is there any real scientific evidence for it?

The density of the moon is anomalous ...

Quote
Densities generally trends towards lower values as the distance from the sun increases ...
The main exception to this rule is the density of the Moon, which owes its lower density to its unusual origin.
http://en.wikipedia.org/wiki/Terrestrial_planet#Density_trends
« Last Edit: 13/12/2010 22:48:14 by RD »
 

Offline Bill S

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Thanks, I'll start looking for Theia information.
 

Offline Don_1

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Can this hypothesis really be given much credence? The coming together of a cloud mass of gasses and solids as a gradual process seems to work fine for me, but the collision of two similar sized bodies just doesn't make sense, unless you consider it to be a precursor to the amalgamation of a cloud mass.

The combined gravitational pull of the two bodies would have been rough the equivalent of Earth's present gravity. Surely this would have lead to an impact which would have caused the two bodies to annihilate each other rather than to fuse together.
 

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