Another wrinkle in planetary internal convection induced dynamo theory b4in.org/aEMF It’s worth reading between the lines of this one to see the perplexed furrows on the brows of the ‘surprised’ scientists. The magnetic fields of planetary building blocks lasted for a surprisingly long time in the solar system’s early days, a new study suggests. = The magnetic fields of these big asteroids were apparently generated by the same process that drives Earth’s global magnetic activity, and could have persisted for hundreds of millions of years after the objects’ formation, researchers said. The study team analyzed pallasites, iron-and-nickel meteorites believed to originate from an ancient rocky body about 250 miles (400 kilometers) wide. The pallasites contain tiny particles of tetrataenite — a mineral that records a magnetic history of the parent body going back billions of years. The researchers probed this history using an X-ray electron microscope at the BESSY II synchrotron in Berlin, capturing the moment when the big asteroid’s global magnetic field died. ”We’re taking ancient magnetic field measurements in nanoscale materials to the highest-ever resolution in order to piece together the magnetic history of asteroids,” study lead author James Bryson, a Ph.D. student at Cambridge University in England, said in a statement. “It’s like a cosmic archaeological mission.” The pallasites’ parent body was one of many relatively large, rocky objects that formed in the first few million years of solar system history. Radioactive decay heated up the interiors of these planetary building blocks, which segregated into molten metal cores surrounded by rocky mantles. More b4in.org/aEMF
Posted on: Fri, 23 Jan 2015 20:44:41 +0000
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