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  • 1
    Publication Date: 2015-05-09
    Description: Magnetized rocks can record the history of the magnetic field of a planet, a key constraint for understanding its evolution. From orbital vector magnetic field measurements of Mercury taken by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft at altitudes below 150 kilometers, we have detected remanent magnetization in Mercury's crust. We infer a lower bound on the average age of magnetization of 3.7 to 3.9 billion years. Our findings indicate that a global magnetic field driven by dynamo processes in the fluid outer core operated early in Mercury's history. Ancient field strengths that range from those similar to Mercury's present dipole field to Earth-like values are consistent with the magnetic field observations and with the low iron content of Mercury's crust inferred from MESSENGER elemental composition data.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Johnson, Catherine L -- Phillips, Roger J -- Purucker, Michael E -- Anderson, Brian J -- Byrne, Paul K -- Denevi, Brett W -- Feinberg, Joshua M -- Hauck, Steven A 2nd -- Head, James W 3rd -- Korth, Haje -- James, Peter B -- Mazarico, Erwan -- Neumann, Gregory A -- Philpott, Lydia C -- Siegler, Matthew A -- Tsyganenko, Nikolai A -- Solomon, Sean C -- New York, N.Y. -- Science. 2015 May 22;348(6237):892-5. doi: 10.1126/science.aaa8720. Epub 2015 May 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada. Planetary Science Institute, Tucson, AZ 85719, USA. cjohnson@eos.ubc.ca. ; Planetary Science Directorate, Southwest Research Institute, Boulder, CO 80302, USA. ; NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. ; The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA. ; Lunar and Planetary Institute, Houston, TX 77058, USA. Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA. ; Institute for Rock Magnetism, Department of Earth Sciences, University of Minnesota, Minneapolis, MN, 55455, USA. ; Department of Earth, Environmental, and Planetary Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA. ; Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA. ; Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA. ; Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada. ; Planetary Science Institute, Tucson, AZ 85719, USA. Department of Earth Sciences, Southern Methodist University, Dallas, TX 75205, USA. ; Institute and Faculty of Physics, Saint Petersburg State University, Saint Petersburg, Russia. ; Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA. Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25953822" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2011-03-26
    Description: Compelling archaeological evidence of an occupation older than Clovis (~12.8 to 13.1 thousand years ago) in North America is present at only a few sites, and the stone tool assemblages from these sites are small and varied. The Debra L. Friedkin site, Texas, contains an assemblage of 15,528 artifacts that define the Buttermilk Creek Complex, which stratigraphically underlies a Clovis assemblage and dates between ~13.2 and 15.5 thousand years ago. The Buttermilk Creek Complex confirms the emerging view that people occupied the Americas before Clovis and provides a large artifact assemblage to explore Clovis origins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Waters, Michael R -- Forman, Steven L -- Jennings, Thomas A -- Nordt, Lee C -- Driese, Steven G -- Feinberg, Joshua M -- Keene, Joshua L -- Halligan, Jessi -- Lindquist, Anna -- Pierson, James -- Hallmark, Charles T -- Collins, Michael B -- Wiederhold, James E -- New York, N.Y. -- Science. 2011 Mar 25;331(6024):1599-603. doi: 10.1126/science.1201855.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for the Study of the First Americans, Departments of Anthropology and Geography, Texas A&M University, College Station, TX 77843-4352, USA. mwaters@tamu.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21436451" target="_blank"〉PubMed〈/a〉
    Keywords: Anthropology, Cultural/*history ; Archaeology ; Geologic Sediments ; History, Ancient ; Humans ; Texas
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2018-12-14
    Description: Paired measurements of 14 C/ 12 C and 230 Th ages from two Hulu Cave stalagmites complete a precise record of atmospheric 14 C covering the full range of the 14 C dating method (~54,000 years). Over the last glacial period, atmospheric 14 C/ 12 C ranges from values similar to modern values to values 1.70 times higher (42,000 to 39,000 years ago). The latter correspond to 14 C ages 5200 years less than calibrated ages and correlate with the Laschamp geomagnetic excursion followed by Heinrich Stadial 4. Millennial-scale variations are largely attributable to Earth’s magnetic field changes and in part to climate-related changes in the oceanic carbon cycle. A progressive shift to lower 14 C/ 12 C values between 25,000 and 11,000 years ago is likely related, in part, to progressively increasing ocean ventilation rates.
    Keywords: Atmospheric Science, Geochemistry, Geophysics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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