Jan. 26, 2009 -- Dating of the oldest-known piece of lunar zircon, brought back from our nearest neighbor in 1972, has pushed back the time when the moon's surface first formed. The landmark find, published online today in Nature Geoscience, has allowed the team of German, Australian and U.S. scientists to give a "precise younger age limit" for the solidification of the moon's surface. Lead author Alexander Nemchin, of Curtin University of Technology, said the moon is generally believed to have formed from the debris of a collision between the earth and a Mars-sized body more than 4.5 billion years ago. Nemchin, a researcher within the Department of Applied Geology, said the heat generated by the coalescing of debris that formed the moon led to the creation of a magma ocean about 500 to 800 kilometers thick. The cooling, or crystallization, of the lunar magma ocean resulted in the moon as we observe it today, he said. Related Content: Get the Latest in Science and Tech News From Discovery How Stuff Works: What If We Lived on the Moon? ABC Science Onilne Nemchin said there has been considerable debate over the precise timing of this crystallization of the magma ocean. "The timing of lunar magma ocean crystallization remains loosely constrained to the first 250 million years of lunar history," he said. However he said analysis of the zircon grains can give a precise timing to this process because zircon is formed during the very last stages of solidification of the magma ocean. Zircon is used to precisely date geological processes in rocks because it contains uranium which decays into lead at a known rate, Nemchin said. By analyzing the ratio of lead and uranium isotopes in the lunar zircon, Nemchin and his colleagues, dated the zircon grain as being 4.42 billion years old. Nemchin said this shows the moon's crust was almost completely formed within about 100 million years. He admits the finding is "only as good as the oldest zircon." "If someone finds older material we can push it further," he said. "But we know [the cooling] is not going to take any longer." Scientists have long known there was zircon on the moon. But after an initial focus on the mineral in the early days of lunar exploration, interest in zircon faded over the past 10-20 years. Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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