Moon Craters a Window to Earth's Past Story by Lonnie Shekhtman (Source: NASA Visualization Explorer) By looking at the Moon a group of scientists is challenging our understanding of a part of Earth’s history. On Earth, asteroid impacts increased by two to three times starting around 290 million years ago. For decades many experts assumed that early Earth craters have been worn away by the wind, storms, and other geologic processes. This idea explained why Earth has fewer older craters than expected compared to other bodies in the solar system, but it made it difficult to find an accurate impact rate and to determine whether it had changed over time. But by studying data on Moon craters from NASA’s Lunar Reconnaissance Orbiter, scientists found the Moon and Earth have historically shared a similar rate of asteroid impacts. The surface of the Moon is riddled with both ancient craters mostly undisturbed by erosion and craters from modern-day impacts making it the most complete and ac...
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