Planet formation

[alokmohan]

UC Davis researchers have dated the earliest step in the formation of the solar system -- when microscopic interstellar dust coalesced into mountain-sized chunks of rock -- to 4,568 million years ago, within a range of about 2,080,000 years. <br /><br />UC Davis postdoctoral researcher Frederic Moynier, Qing-zhu Yin, assistant professor of geology, and graduate student Benjamin Jacobsen established the dates by analyzing a particular type of meteorite, called a carbonaceous chondrite, which represents the oldest material left over from the formation of the solar system. <br /><br />The physics and timing of this first stage of planet formation are not well understood, Yin said. So, putting time constraints on the process should help guide the physical models that could be used to explain it. <br /><br />In the second stage, mountain-sized masses grew quickly into about 20 Mars-sized planets and, in the third and final stage, these small planets smashed into each other in a series of giant collisions that left the planets we know today. The dates of those stages are well established. <br /><br />Carbonaceous chondrites are made up of globules of silica and grains of metals embedded in black, organic-rich matrix of interstellar dust. The matrix is relatively rich in the element manganese, and the globules are rich in chromium. Looking at a number of different meteorites collected on Earth, the researchers found a straight-line relationship between the ratio of the amount of manganese to that of chromium, the amount of matrix in the meteorites, and the amount of chromium-53. <br /><br />These meteorites never became large enough to heat up from radioactive decay, so they have never been melted, Yin said. They are "cosmic sediments," he said. <br /><br />By measuring the amount of chromium-53, Yin said, they could work out how much of the radioactive isotope manganese-53 had initially been present, givinghttp://www.spaceref.com/news/viewpr.nl.html?pid=24369

 

[Swampcat]

Sheesh...I could quickly make Galaxy just correcting your cut-and-paste errors <img src="/images/icons/tongue.gif" />.<br /><br /><font color="orange">By measuring the amount of chromium-53, Yin said, they could work out how much of the radioactive isotope manganese-53 had initially been present, giving an indication of age.</font><br /><br />Rest of SpaceRef article <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>