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omegaman 07-27-2012 02:17 PM

Moon formation: Was it a 'hit and run' accident?

Captain Tom Coughlin 07-27-2012 02:34 PM

It's like a solar system equivalent to hitting a parked car

omegaman 07-27-2012 02:49 PM


Originally Posted by Captain Tom Coughlin (Post 325601)
It's like a solar system equivalent to hitting a parked car

The universe is one big game of billiards or pool! Sooner or later you end up in the corner pocket courtesy of something with your number on it!

omegaman 07-27-2012 02:51 PM

What happened to "Th-ia" Is it still out there, merrily making its way back to take a second swipe after all this time?

Auto spell kept correcting Th-ia as This.

Captain Tom Coughlin 07-27-2012 02:57 PM

Maybe it went rouge and left the solar system

Saquist 07-27-2012 06:53 PM

I'm still not convinced on the moon coming from earth with Giant impact. Earth shows no such large scar.

This idea seems more likely for an even distribution of matter and the creation of the moon.

Zhang explains that it's unlikely Earth could have exchanged titanium gas with the magma disk because titanium has a very high boiling point. "The oxygen isotopic composition would be very easily homogenized because oxygen is much more volatile, but we would expect homogenizing titanium to be very difficult."
So, if the giant impact hypothesis doesn't explain the moon, how did it get there? One possibility is that a glancing blow from a passing body left Earth spinning so rapidly that it threw some of itself off into space like a shot put, forming the disk that coalesced into the moon. This would explain why the moon seems to be made entirely of Earth material. But there are problems with this model, too, such as the difficulty of explaining where all the extra angular momentum went after the moon formed, and the researchers aren't claiming to have refuted the giant impact hypothesis.

Captain Tom Coughlin 07-27-2012 06:54 PM

Earth would not show a scar.

Saquist 07-27-2012 08:51 PM

Earth would definitely show a scar. The Erosion argument is over played. And where as every other planet has evidence of a large impact (Mars and Venus) Earth is the only one that has plate tectonics where as scientist believe that the impact some how terminated plate tectonics. (Likely melting the entire surface)

Moon creation Theory places the impact at 4.5 billion years.
They project plate tectonic 3.6 billion years ago. (900 million gap)
Earth's oldest Sedimentary rocks are 3.9 million years old.
Oldest Rocks on the moon are 4.8 million years old.

Moon rocks have evidence of being molten. (the complete surface)
Earth's rocks have no such evidence. Our rocks show that Earth earth's heavy elements aren't shifted toward the core. They are still on the surface sprinkled randomly just like accretion would allow. If there was a massive impact then Earth really shouldn't have plate tectonics either and should have a cleanly separated density of materials. Nor should it have any water.

That's why they came up with the cometary bombardment theory to bring water to Earth but still no other planet in the inner solar system has that characteristic either. Essentially the moon should have water in permanently dark craters in ice form.

The Great Collision Theory just doesn't add up.

omegaman 07-27-2012 09:04 PM

Saquist, wouldn't the Earth have had molten crust at the stage of impact, which would explain the absence of any scarring?

Saquist 07-28-2012 07:28 AM

Apparently not. I always thought that was true way back when but currently from what I've read planetary formation can happen very quickly. From the time the sun formed to 100,000 years is the cap for planets growing from the nebula. Further growth happens by collisions. This time period would have been extremely volatile and prevented water from forming because it vaporizes at too low a temperature but hundreds of millions of years later Earth's surface and atmosphere may have been high but from what I've read...not what you would call molten at this point. It would be like Venus.

Remember the solar system was in a molecular dust cloud high in temperature because of the sun but if the temperature was too high it would be hard for the planets to form from the excited gases. Accretion happens quickly and gradually. It would make rocks 200 meters wide and then those rocks would accrete together. A good example of this is looking at asteriods which are huge collections of Rocks held together by dust and ice. Earth would have been held together by it's own mass from heavy elements that came together first like nickel and iron. Everything else gathered around that or impacted the planet during the heavy bombardment. They believe collisions are how the planets got to this size but apparently the moon formation is far removed from the initial formation of the solar system where large planetoids were especially numerous, although still frequent.

(At the same time take what I say with a grain of salt. Orogenesis is not my field of intense interest so I'm familiar with somethings and the processes but not as familiar with the time line.)

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