Re: Earth's Axial Tilt (posted for R. Vollbrecht)

[N.MacLeod@xxxxxxxxx (N. MacLeod)]

X-Sender: rvollbr@popper.gwdg.de
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Date: Fri, 15 Dec 1995 22:19:01 +0000
To: paleonet-owner@nhm.ac.uk
From: Ruediger Vollbrecht <rvollbr@uni-goettingen.de>
Subject: Re: Earth's Axial Tilt (posted for T. Hansen)
Status: O

>From: Thor A Hansen <thorenet@henson.cc.wwu.edu>
>To: paleonet-owner@nhm.ac.uk
>Cc: paleonet@nhm.ac.uk
>Subject:  Earth's Axial Tilt
>Mime-Version: 1.0
>Status: O
>
>
>Does anybody know if the young Earth (about 4 billion years ago) is
>thought to have had a different degree of tilt than it does now?
>

There is some reason to believe tilt  was different before that time. As far
as I know, the Earth-Moon system experienced a very heavy cosmic bombardment
at around 4.0 - 3.8 billion years ago. Many of the craters you see on the
lunar surface today are of that age. Moon itself is supposed to be somewhat
older, I think.

The size of some of the craters and maria on Moon indicates that part of the
impactors must have been really huge. You don't find similar craters on
earth because it has a dynamic surface. It is thought by some that the
biggest impactors were able to tilt earth's axis from the "vertical" (or
better, from the direction initially inherited from a rotating gas cloud).

As soon as you start believing in this you wonder what kind of cosmic
monsters threw Uranus on its side and toppled Venus over...

Anyway, I would expect a different tilt by the time you mentioned -- but I'm
no expert, I just quoted from what I have read over the years..

Ruediger Vollbrecht
Dept. of Sedimentary Geology
Goettingen, Germany
rvollbr@uni-goettingen.de