Saturday, January 06, 2007

How to tell if a rock fell from outer space

Next time when a rock comes crashing into your house, it would be good if you can tell if it really fell from outer space or if it's just another gift from that evil neighbour of yours. From Slate:
First, look at it. A freshly fallen meteorite will have a smooth coating of black or dark brown fusion crust. The coating forms as it enters the Earth's atmosphere, when the outer layer of rock begins to melt. This can result in thumbprintlike indentations (called regmaglypts) on the surface of the meteorite; the subsequent cooling-off often produces a set of cracks in the fusion crust. (Experts say the object found in New Jersey looks like it might have a fusion crust.)

Next, pick it up. Meteorites are denser than regular rocks and feel heavier than they look. The New Jersey object reportedly weighs as much as a can of soup, even though it's the size of a golf ball. You can also try running a magnet over the object—most kinds of meteorites will attract it.

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