Talk:Giant impact hypothesis
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Possible new evidence
I found a reference to possible new evidence for a giant impact:
"Seismic data indicate that the western and eastern hemispheres of Earth's inner core differ, and this has led some to suggest that the core was once subjected to an impulse - presumably from the collision of a space rock or planetoid which shook the whole Earth."
I have been unable to find the "some" who are suggesting this. It is not mentioned in the scientific report the article is based on: http://www.nature.com/srep/2013/130628/srep02096/full/srep02096.html
I have emailed the author of the BBC article Professor Simon Redfern of the University of Cambridge http://www.esc.cam.ac.uk/people/academic-staff/simon-redfern
in order to try to ascertain if there is any proper source to quote from.
Alas Professor Redfern says "The suggestion to which I alluded was a verbal comment once made to me at a conference. It turns out, on further investigation, that I" too cannot find any written record of such a hypothesis. Indeed, the closest I can find is the work of Deguen and co-workers."
The new evidence can be found in the journal Science, and can be accessed at the following web page: http://www.sciencemag.org/content/344/6188/114 "Identification of the giant impactor Theia in lunar rocks" Science 6 June 2014: Vol. 344 no. 6188 pp. 1146-1150 DOI: 10.1126/science.1251117
Query re GRAIL ruling out minor Theia impact debris causing lunar locking
This article currently says:
“The resulting mass irregularities would subsequently produce a gravity gradient that resulted in tidal locking of the Moon so that today, only the near side remains visible from Earth. However, mapping by the GRAIL mission has apparently ruled out this scenario.”
Yes, I would like to see a citation. As far as I can tell the official report merely indicates that gravitational anomalies are indeed caused by early impacts when the Lunar mantle was soft and you can see from the crustal thickness map in the PDF that these seem to be caused by five concentrated events penetrating to the Lunar mantle or very near, with one hemisphere less effected. (Also, the PDF report says the lunar refractory element composition is similar to that of Earth.)
The crust of the Moon seems thicker on one side according to the GRAIL report above. This matches an earlier description of the issue at http://www.bbc.co.uk/news/science-environment-14391929
What happened to Theia?
...after it had collided with the Earth? Had it moved beyond our solar system unnoticed or is now one of the known planets? — Preceding unsigned comment added by 18.104.22.168 (talk) 11:27, 19 May 2014 (UTC)
I'm not sure how useful this'd be from a scan of the article, but this may be of use: http://www.bbc.co.uk/news/science-environment-27688511 Irockz (talk) 01:39, 7 June 2014 (UTC)