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Posted by Jonathan Silverlight on May 6, 2006, 1:36 pm
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>I saw a comment recently regarding Mercury. Due to its iron-rich
>composition and proximity the sun, there's a possibility that the
>innermost planet may have started out as something of a gas giant at
>the time of solar ignition. How unlikely does this theory sound? If
>something like Saturn has a sun ignite next to it, does it wind up like
>another Mercury?
I was able to find a discussion on this idea at
<http://www.bautforum.com/showthread.php?t=5141>
Unless I missed it, they don't mention the idea that Mercury as we see
it is just the core of a much bigger planet, most of which was removed
in a huge collision, or that "hot Jupiters" are supposed to have formed
in the outer solar system and migrated inward. They can't form where
they are seen, but they can survive for billions of years.
I found another interesting reference "GAS _RING_ MODEL FOR THE ORIGIN
OF MERCURY" [my emphasis]
,http://www.lpi.usra.edu/meetings/mercury01/pdf/8061.pdf>
>
>And closer to home, why does the Lunar crater Aristarchus seem such an
>anomaly, amidst the surrounding Maria? Has the composition of the
>crater's floor been dated? Should Aristarchus -- according to
>prevailing opinion -- have experienced the effect of infilling?
Aristarchus is one of the youngest large craters - only 450 million
years old according to
<http://en.wikipedia.org/wiki/Aristarchus_(crater)> although
<http://hubblesite.org/newscenter/newsdesk/archive/releases/2005/29/image/l>
gives a much wider range of 100 to 900 million years - no-one has yet
explored inside a big crater or returned samples, which is a major
failure of lunar exploration IMHO :-)
>
>Also, is it possible that Terrestrial Continental Drift occurs in
>conjunction with geographical polar wander? At the time when the north
>pole was located in northern Africa, did the Earth display the single
>landmass of Pangea?
Corrections welcomed, but has there ever been a time when the geographic
pole was very far from its current position? I thought it was argued
that the Moon stabilised the rotation of the Earth so it never wanders
very far. "Polar dinosaur" fossils have been found in Australia, a long
way from their point of origin below the Antarctic Circle.
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