[moon] The Moon’s Origin Story Is in Crisis … new science is causing the story of the moon’s creation to be reevaluated … ‘The astronauts chiseled bits of the moon from the boulder. Then, using a rake, Schmitt scraped the powdery surface, lifting a rock later named troctolite 76536 off the regolith and into history. That rock, and its boulder brethren, would go on to tell a story of how the entire moon came to be. In this creation tale, inscribed in countless textbooks and science-museum exhibits over the past four decades, the moon was forged in a calamitous collision between an embryonic Earth and a rocky world the size of Mars. This other world was named Theia, for the Greek goddess who gave birth to Selene, the moon. Theia clobbered Earth so hard and so fast that the worlds both melted. Eventually, leftover debris from Theia cooled and solidified into the silvery companion we have today. But modern measurements of troctolite 76536, and other rocks from the moon and Mars, have cast doubt on this story. In the past five years, a bombardment of studies has exposed a problem: The canonical giant-impact hypothesis rests on assumptions that do not match the evidence. If Theia hit Earth and later formed the moon, the moon should be made of Theia-type material. But the moon does not look like Theia—or like Mars, for that matter. Down to its atoms, it looks almost exactly like Earth.’
This entry was posted on Wednesday, August 30th, 2017 at 12:31 pm and is filed under Space.