HR: 15:10h
AN: GP22A-07    [PDF]
TI: Shock effects on Martian crustal magnetization near large impact basins
AU: * Kletetschka, G
AF: Catholic University of America, Department of Physics, Cardinal Station, Wasgington DC, DC 20064 United States
AU: * Kletetschka, G
AF: Institute of Geology, Academy of Sciences, Rozvojova 135, Prague, 16500 Czech Republic
AU: Connerney, J E
AF: GSFC/NASA, Code 695, Greenbelt, MD 20771 United States
AU: Just, J
AF: Geologisch-Palaeontologisches Institut, INF 234, Heidelberg, D-69120 Germany
AU: Ness, N F
AF: Geologisch-Palaeontologisches Institut, INF 234, Heidelberg, D-69120 Germany
AU: Acuna, M H
AF: Bartol Institute, University of Delaware, 217 Sharp lab, Newark, DE 19716 United States
AB: The Martian crust has been subject to several very large meteoroid impacts. Shock pressures associated with these impacts may have demagnetized parts of the Martian crust to an extent determined by the shock resistance of the magnetic materials responsible for crustal sources. Impacts that form large basins generate pressures in excess of 1 GPa that extend several crater radii from the point of impact, beneath the surface. Near the surface, however, wave interference significantly reduces the pressure (1 GPa) experienced by crustal materials. Impact demagnetization experiments indicate that pressures of 1 GPa magnitude are sufficient to demagnetize most of the common magnetic minerals (magnetite, pyrrhotite). Titanohematite with ferrian ilmenite exsolution lamellae is the exception. According to our data, this mineral has the highest coercivity ($>$300 mT) and largest NRM intensity (~1500 A/m). As such it is a leading candidate for Mars crustal magnetism, particularly in proximity to the large impact basins where pressures $>$ 1 GPa may have been experienced. The presence of this mineral suggests that much of the deep Martian crust was oxidized at the time of acquisition of magnetic remanence. This would be an important constraint for Martian chemical evolution at the time of crustal formation.
DE: 1517 Magnetic anomaly modeling
DE: 1519 Magnetic mineralogy and petrology
DE: 1521 Paleointensity
DE: 5420 Impact phenomena (includes cratering)
DE: 5440 Magnetic fields and magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting