Jim, Here, Here. We Earthlings are very fortunite to have the right conditions to keep us happy, well most of us anyway. My point is, we are the way we are because the Earth's environment, through evolution, made sure we are suited to live here. The interesting point is, Mars is now not as fortunite. It too once had a magnetosphere. It is thought to have a ferro-magnesium core as the Earth has, it once had a liquid outer core and very active volcanism. What it didn't have was a large moon that kept tugging on it keeping it churned up in side. Mars' once had a much denser atmosphere with more oxygen than it does today. but when the volcanism stopped, additional gasses were not introduced to the atmosphere and the planet lost its magnetosphere because the outer core solidified. Without this magnetosphere, the solar winds started stripping the planet of much of its atmosphere. As for Earth, if the impact theory is correct, it may have added some mass to the ferro-magnesium core but it probably didn't add it all. By the average density of the rocky planets (Mercury, Venus, Earth and Mars), it appears that all have a ferro-magnesium core. Geologically, our moon plays a very important role in conditions here on Earth. Also, the impact theory answers several questions about clues we find in the geologic record here on Earth. I personally believe the impact theory to be spot-on. Rodger Fry ----- Original Message ----- From: "jim Gibson" <jimgibson0@gmail.com> To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Sent: Sunday, May 24, 2009 8:35 AM Subject: [Utah-astronomy] The wow factor It being Sunday I may be feeling more philosophical than scientific. I am thinking of the moon and the many things it does for the benefit of life on earth. Although the Giant Impact Theory has been around for a long while, I first read about Dr. Robin Canup’s work back in 2003 where she and her group created a computer modeled simulation of a mars size planet impacting the earth at an oblique angle a good while before cockroaches. The theory explains how the earth got a good sized molten iron core, why the earth is tilted 23 degrees, how the earth got it’s current rotation rate, and more. Whether the theory is true or not is not my point here. The fact is, those items I just mentions (core, tilt, and rotation) are generally accepted as true and it was reading about the Giant Impact Theory that enlightened my mind to those very basic facts. The magnetosphere generated by the molten-circulating core that protects the earth from the sun’s rude blast is a wonder. Mars is not so fortunate. The tilt of 23 degrees that allow for seasons is a wonder. The rotation rate to allow for a 24 hour day is great because if I sleep any longer then 6 hours my back hurts. If it was any shorter, I would never get a polar alignment + drift method done in time. Just these few facts alone when considered together would seem to make anyone just want to go “Wow! We are blessed!” http://en.wikipedia.org/wiki/Giant_impact_hypothesis http://www.psi.edu/projects/moon/moon.html Jim _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com