Announcement from Planetary Science Research Discoveries [PSRD]
New article online:
Mars Crust: Made of Basalt-- Chemical analyses of rocks on the Martian surface indicate that the Martian crust was built of basalt lava flows not much different from those on Earth.
FULL ARTICLE at:
http://www.psrd.hawaii.edu/May09/Mars.Basaltic.Crust.html
Showing posts with label Hawaii Institute of Geophysics and Planetology. Show all posts
Showing posts with label Hawaii Institute of Geophysics and Planetology. Show all posts
08 May 2009
29 March 2009
Time to Solidify an Ocean of Magma -Lunar Study 29MAR09
Time to Solidify an Ocean of Magma
25MAR09
--- A small mineral grain places limits on how long it took the lunar magma ocean to solidify.
Written by G. Jeffrey Taylor
Hawai‘i Institute of Geophysics and Planetology
Cosmochemists are reasonably sure that a global ocean of magma surrounded the Moon when it formed. This was a monumentally important event in lunar history, forming the primary feldspar-rich crust of the lunar highlands and setting the stage for subsequent melting inside the Moon to make additional crustal rocks. Numerous questions remain about the complex array of processes that could have operated in such a huge amount of magma, and about how long it took to solidify the magma ocean. Alex Nemchin and colleagues at Curtin University of Technology (Australia), Westfäilische Wilhelms-Universität (Münster, Germany), and the Johnson Space Center (Houston, Texas, USA) dated a half-millimeter grain of the mineral zircon (ZrSiO4) in an impact melt breccia from the Apollo 17 landing site. They used an ion microprobe to measure the concentrations of lead and uranium isotopes in the crystal, finding that one portion of the grain recorded an age of 4.417 ± 0.006 billion years. Because zircon does not crystallize until more than 95% of the magma ocean has crystallized, this age effectively marks the end of magma ocean crystallization. Magma ocean cooling and crystallization began soon after the Moon-forming giant impact. Other isotopic studies show that this monumental event occurred 4.517 billion years ago. Thus, the difference between the two ages means that the magma ocean took 100 million years to solidify.
Reference:
Nemchin, A., Timms, N., Pidgeon, R., Geisler, T., Reddy, S., and Meyer, C. (2009) Timing of Crystallization of the Lunar Magma Ocean Constrained by the Oldest Zircon. Nature Geoscience, 25 January 2009: doi: 10.1038/NGEO417.
MORE with photos: http://www.psrd.hawaii.edu/Mar09/magmaOceanSolidification.html
25MAR09
--- A small mineral grain places limits on how long it took the lunar magma ocean to solidify.
Written by G. Jeffrey Taylor
Hawai‘i Institute of Geophysics and Planetology
Cosmochemists are reasonably sure that a global ocean of magma surrounded the Moon when it formed. This was a monumentally important event in lunar history, forming the primary feldspar-rich crust of the lunar highlands and setting the stage for subsequent melting inside the Moon to make additional crustal rocks. Numerous questions remain about the complex array of processes that could have operated in such a huge amount of magma, and about how long it took to solidify the magma ocean. Alex Nemchin and colleagues at Curtin University of Technology (Australia), Westfäilische Wilhelms-Universität (Münster, Germany), and the Johnson Space Center (Houston, Texas, USA) dated a half-millimeter grain of the mineral zircon (ZrSiO4) in an impact melt breccia from the Apollo 17 landing site. They used an ion microprobe to measure the concentrations of lead and uranium isotopes in the crystal, finding that one portion of the grain recorded an age of 4.417 ± 0.006 billion years. Because zircon does not crystallize until more than 95% of the magma ocean has crystallized, this age effectively marks the end of magma ocean crystallization. Magma ocean cooling and crystallization began soon after the Moon-forming giant impact. Other isotopic studies show that this monumental event occurred 4.517 billion years ago. Thus, the difference between the two ages means that the magma ocean took 100 million years to solidify.
Reference:
Nemchin, A., Timms, N., Pidgeon, R., Geisler, T., Reddy, S., and Meyer, C. (2009) Timing of Crystallization of the Lunar Magma Ocean Constrained by the Oldest Zircon. Nature Geoscience, 25 January 2009: doi: 10.1038/NGEO417.
MORE with photos: http://www.psrd.hawaii.edu/Mar09/magmaOceanSolidification.html
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