On Jan 3, 9:57 pm, Tom Adams <[email protected]> wrote: > Really? Do you think Earth ran around like a short stop and caught > them all? How the heck could little ole Earth's cross-section > (relative to the vastness of its obital cross secton) protect Venus?
Earth would not act as a backstop to regular comets coming from the the Oort and Kuiper belts, but if the Main (asteroid) Belt Comets, with circular orbit gradually became more elliptical they would crash with Earth first, and not become elliptical enough to crash with Venus. These are asteroids that formed beyond the snowline. Of course icy asteroids forming further from the snowline would be more likely to be disturbed by Jupiter and crash into Earth. http://www2.ess.ucla.edu/~jewitt/papers/2006/F06.pdf Here is a news release which is a little more explicit: http://www.hawaii.edu/news/article.php?aId=1379 Note, a couple of telling points. Earth formed within the snowline so it should have been dry. The H/D ratio of Earth's water does not match that of comets, or of meteoric water from the Earth's mantle. The late heavy bombardment has not yet been explained, but could have been caused by the adjustment of the orbits Jupiter and Saturn disrupting the orbits of the outer asteroids which were beyond the snowline. See also: http://www.ifa.hawaii.edu/~meech/NAIJC/papers/gaidos_jc2.pdf Here's a list of Jewitt's publications, which will be useful if you want to follow this up. http://www2.ess.ucla.edu/~jewitt/bib.html Not sure if that will convince you, but it makes sense to me. Cheers, Alastair. -- You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/globalchange
