Issue Date: May 13, 2013
Earth And Moon Share Water Source
Two years ago, scientists discovered that bubbles of preserved magma in ancient rocks on Earth’s moon contained large amounts of water, a finding that contradicted the notion that the moon has always been bone-dry. Now, the same group, headed by Alberto E. Saal of Brown University, finds that this lunar water has the same isotopic composition as water on Earth, implying that Earth and its moon have a common water source (Science 2013, DOI: 10.1126/science.1235142 ). The group examined samples of moon rocks returned to Earth from the Apollo 15 and 17 missions. Earth’s water is believed to have been seeded by carbonaceous chondrites, which are common meteorites hailing from an asteroid belt near Jupiter. Because the moon was likely formed from debris flung from the impact of a Mars-sized asteroid on the nascent Earth, the new finding suggests that Earth was already wet at the time of impact. Researchers have also assumed that the moon’s lighter elements, such as hydrogen, would have boiled off into space after the impact, but this idea may need to be rethought, the authors say.
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