Early interactions with the Earth may have heated up the Moon and caused it to remelt, producing new lunar rocks and erasing old craters.
You don't look a day over 4.35 billion! Here's the moon's anti-aging secret toggle caption NASA The Moon has long been the Earth's close companion, but researchers have struggled to understand exactly when the moon formed, because tiny crystals in the moon rocks brought home by astronauts suggested two different ages. Now, a study in the journal Nature argues for the earlier age, saying that the ancient Moon also went through a period when it got hot and partially remelted, producing new rocks about 4.35 billion years ago. The rock-melting heat came from early gravitational interactions with the Earth, which stretched and squeezed the Moon, warming it up. This process is called "tidal heating." It is how Jupiter currently heats up its moon Io, the most volcanically active spot in the solar system. Sponsor Message "We think that the Moon went through a period when it looked like Io, and for the same reason," says Francis Nimmo , a planetary scientist with the University of California, Santa Cruz. "There would have been volcanoes jetting off all over the place," he says. "It would have been very dramatic." The result would be a Moon that seemed younger than its true age. A spectacular collision Astronomers have long known that the Earth and Moon are younger than 4.6 billion years, because that's when the solar system got its start. A huge cloud of dust and gas collapsed inward, forming a new star. Leftover clumps of matter started crashing into each other, glomming together and gradually building up planets. During this chaotic time, an object the size of Mars smashed into the proto-Earth. "It would surely have been spectacular," says Nimmo. "It was just so energetic that it's really hard for us to conceive of what it must have looked like." The crash would have liquified the Earth and vaporized some of it, along with producing the Moon. Back…