HR: 10:50h
AN: GP42A-03    [Abstracts]
TI: Investigating Impact Demagnetization Through Laser Impacts and SQUID Microscopy
AU: * Gattacceca, J
EM: gattacceca@cerege.fr
AF: CEREGE, CNRS/Universit‚ Aix-Marseille3, BP 80, Aix-en-Provence Cdx4, 13545 France
AU: Weiss, B P
EM: bpweiss@MIT.EDU
AF: Dept of Earth, Atmospheric and Planetary Sciences, MIT, 77 Massachussets avenue, Cambridge, MA 02139 United States
AU: Boustie, M
EM: boustie@lcd.ensma.fr
AF: Laboratoire de Combustion et de D‚tonique, ENSMA, BP 40109, Futuroscope Cedex, 86961 France
AU: Rochette, P
EM: rochette@cerege.fr
AF: CEREGE, CNRS/Universit‚ Aix-Marseille3, BP 80, Aix-en-Provence Cdx4, 13545 France
AU: Lima, E A
EM: eduardo.a.lima@vanderbilt.edu
AF: Dept of Physics and Astronomy, VU Station B 351631, Nashville, TN 37235-1631 United States
AU: Fong, L E
EM: l.fong@vanderbilt.edu
AF: Dept of Physics and Astronomy, VU Station B 351631, Nashville, TN 37235-1631 United States
AU: Baudenbacher, F
EM: f.baudenbacher@vanderbilt.edu
AF: Dept of Physics and Astronomy, VU Station B 351631, Nashville, TN 37235-1631 United States
AB: Hypervelocity impacts may play a crucial role in the magnetic records of many extraterrestrial bodies (asteroids, Mars, the Moon...). The understanding of demagnetization by hypervelocity impacts is crucial for the interpretation of planetary magnetic anomalies and of the paleomagnetic signal of meteorites. We propose an innovative approach to investigate the effects of impacts on the remanent magnetization of geologic materials. It consists of the combination of pulsed laser impacts and room temperature scanning SQUID microscopy. Laser impacts, besides being non-destructive, can reach several hundreds of GPa and allow well-calibrated modeling of shock wave propagation within the impacted samples. High-resolution SQUID microscopy allows mapping of the magnetic field with an unprecedented spatial resolution of about 100 æm. We present the shock modeling and magnetic field data obtained for two laser impacts on a magnetite-bearing basalt sample. Magnetic measurements evidence a demagnetized area at the impact locations, and we show that, for a single laser shot, high-resolution magnetic measurements combined with high-resolution impact modeling provide a continuous relation between the demagnetization intensity and the peak pressure suffered by the sample [see Gattacceca et al., Geology, in press]. This promising technique will allow the investigation of the demagnetization behavior of a variety of geological materials upon impacts. The planned development of this methodology on samples with varied well-characterized magnetic properties and mineralogy, as well as experiments in a controlled, non zero magnetic field, should provide strong insights to the understanding of the magnetization of extraterrestrial materials (interpretation of the magnetic anomalies of Mars and the Moon, as well as the deciphering of the paleomagnetic signal of meteorites) and of terrestrial impact structures.
DE: 1533 Remagnetization
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005