Meteorite dating

“The Sahara was green 5,000 years ago, but the Atacama has been arid for at least 7 million years and maybe as long as 20 million years.” The team subjected a sample of 54 rocky meteorites to cosmogenic age dating using the chlorine-36 isotope and found that the oldest samples fell to Earth between 1 and 2 million years ago, with a mean age of 710,000 years, making this the oldest meteorite collection found to date on Earth’s surface.“This confirms the long-term, multi-million-year stability of the Atacama Desert surfaces and offers a unique opportunity to study the meteorite flux to Earth and meteorite weathering over the million-year time scale,” the team wrote in .The precise decay rate of radioactive elements is used as a clock: the number of daughter products in one rock indicates its age.The oldest meteorites ever dated in the Solar System are 4,56 billion years old, the oldest minerals on Earth are 4,4 billion years old, and the oldest rocks on Earth are 4 billion years old.“It’s an interesting and important result that they found an overabundance of H chondrites between 1 and 0.5 million years ago,” Heck says.“When one type of meteorite dominates, it’s most likely related to an event such as a collision that released those objects from the parent body.” For a follow-up study, Drouard’s team could use cosmic ray exposure dating to determine how long the meteors traveled through space before entering Earth’s atmosphere, Heck says.

Processed meteorites are fragments of larger asteroids and therefore can be metallic like a planet's core or rocky like its mantle or crust.The compositions of processed meteorites are similar to the crusts, mantles or cores of the terrestrial planets.Thus, they must be fragments of larger asteroids whose interiors melted so that the heavier metals sank to the center and the lighter rocks rose to the surface.Some can be distinguished from terrestrial rocks by their metal content, which is high enough to attract a magnet.Primitive meteorites appear to be remnants of the birth of the solar system.

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