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Moon Earth Space Science

Moon Had Magnetic Field At Least a Billion Years Longer Than Thought, Says Study (theguardian.com) 41

While the moon has no global magnetic field nowadays, it did have one in the past and researchers believe it lasted at least a billion years longer than previously thought. The Guardian reports: Between 4.25 billion and 3.56 billion years ago, the lunar magnetic field was similar to that of the Earth. The field is thought to have been generated by the churning movement of fluids within the moon's molten core -- a sort of lunar dynamo. But scientists have long puzzled over when the magnetic field disappeared, with previous research unable to tell whether the field had disappeared completely by 3.19 billion years ago or had lingered on in a weaker form. Writing in the journal Science Advances, Sonia Tikoo, a planetary scientist and co-author of the research from Rutgers University, and colleagues from the University of California, Berkeley and Massachusetts Institute of Technology, describe how they set about unpicking the conundrum by analyzing a lunar rock brought back by the Apollo 15 mission in 1971. The sample contains fragments of basalt that had broken off larger rocks. According to a dating technique based on the ratio of different isotopes of argon, the basalt formed from lava flows about 3.3 billion years ago. These fragments are bound together in the sample by a glassy material, which the team say probably formed when some of the basalt melted following a meteorite impact. The researchers dated the formation of the glassy material to between 1 billion and 2.5 billion years ago. Crucially, the impact also melted iron-containing grains within the basalt. These crystalized again within the glassy material as it quickly cooled, capturing a record of the magnetic field of the moon at that time.

Moon Had Magnetic Field At Least a Billion Years Longer Than Thought, Says Study

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  • by aliquis ( 678370 ) <dospam@gmail.com> on Thursday August 10, 2017 @03:41AM (#54981581) Homepage

    "The upshot, says Tikoo, is that the lunar dynamo was still going until somewhere between one billion and 2.5bn years ago."

    Based on crystallized iron-grains in some glassy material, not very precised timing.

    "Such a field is 1,000 times stronger than that measured at the moonâ(TM)s Apollo 15 landing site by astronauts, and far stronger than than would be expected from the influence of the Earthâ(TM)s magnetic field."

    You are welcome.

  • Moonsanto

    http://humansarefree.com/2015/03/is-moon-artificial-alien-base.html

  • by dcw3 ( 649211 )

    "The researchers dated the formation of the glassy material to between 1 billion and 2.5 billion years ago. "

    How do you go about dating something that doesn't have carbon, or layers of sediment to compare with? I'm sure there are other methods, but the article doesn't elaborate.

    • Re:How? (Score:5, Informative)

      by Applehu Akbar ( 2968043 ) on Thursday August 10, 2017 @08:38AM (#54982335)

      How do you go about dating something that doesn't have carbon, or layers of sediment to compare with? I'm sure there are other methods, but the article doesn't elaborate.

      Biologists use carbon dating because living organisms incorporate stable 12C and radioactive 14C into their bodies in the same ratio as in the surrounding environment, which is assumed not to change with time. After death, when the organism stops incorporating carbon, the 14C steadily decays at a constant rate, enable time-since-death to be computed. C dating is accurate out to about 50,000 years.

      Geologists use the same system of dating, but with isotopes that have half-lives long enough for the measurement to be viable over geologic time spans.

      • by dcw3 ( 649211 )

        I'm puzzled why this is marked informative. My question wasn't looking for an explanation of how carbon dating works, but rather how you date something that doesn't/didn't have carbon. There's no carbon half-life to examine in moon rocks, right??? Or did I have a complete brain freeze here?

        • I'm puzzled why this is marked informative. My question wasn't looking for an explanation of how carbon dating works, but rather how you date something that doesn't/didn't have carbon. There's no carbon half-life to examine in moon rocks, right??? Or did I have a complete brain freeze here?

          Their last sentence. The same method is used but they don't use C but some other element using Radiometric Dating [wikipedia.org]. Probably several other elements and their ratios at creation and the present from a mineral sample where Rubidium-strontium Dating [wikipedia.org] is mentioned for determining the age of lunar samples.

  • "Moon Had Magnetic Field At Least a Billion Years Longer Than Thought"

    But wait! How long is thought?

  • So, just how long has the Moon been sentient?

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