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Mare Basalt

This igneous rock was collected from one of the darker areas on the moon known as mare. The mare formed billions of years ago. Large meteorites impacted the surface of the moon and broke up the crust. Later lavas formed by melting of rock within the moon due to the decay of radioactive elements. The broken crust under the big impact craters allowed the lava to come to the surface. Over time the craters came to be filled with lava flows. This basalt sample, estimated to be 3.7 billion years old, was collected by Apollo 17 astronauts.

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