0800h
AN: P41A-02
TI: Magnetic Signatures of Impact Fractured Rocks from Sierra Madera, Texas, USA - Implications to Magnetic Anomalies on Mars
AU: * Adachi, T
EM: tomoko.adachi@gsfc.nasa.gov
AF: Department of Physics, Catholic University of America, 200 Hannan Hall, Washington, DC 20064, United States
AU: * Adachi, T
EM: tomoko.adachi@gsfc.nasa.gov
AF: Division of Solar System Exploration, Goddard Space Flight Center, NASA, Greenbelt, MD 20771, United States
AU: Kletetschka, G
EM: gunther.kletetschka@gsfc.nasa.gov
AF: Department of Physics, Catholic University of America, 200 Hannan Hall, Washington, DC 20064, United States
AU: Kletetschka, G
EM: gunther.kletetschka@gsfc.nasa.gov
AF: Division of Solar System Exploration, Goddard Space Flight Center, NASA, Greenbelt, MD 20771, United States
AU: Kletetschka, G
EM: gunther.kletetschka@gsfc.nasa.gov
AF: Institute of Geology, and Academy of Science, Rozvojova 6, Praha, 16000, Czech Republic
AU: Wasilewski, P J
EM: Peter.J.Wasilewski@nasa.gov
AF: Division of Solar System Exploration, Goddard Space Flight Center, NASA, Greenbelt, MD 20771, United States
AU: Mikula, V
EM: mikula.vilem@ssedmail.gsfc.nasa.gov
AF: Department of Physics, Catholic University of America, 200 Hannan Hall, Washington, DC 20064, United States
AU: Mikula, V
EM: mikula.vilem@ssedmail.gsfc.nasa.gov
AF: Division of Solar System Exploration, Goddard Space Flight Center, NASA, Greenbelt, MD 20771, United States
AB: Mars Express Orbiter (sounding radar data) revealed that craters of ancient origin had been covered by thick sediments in northern hemisphere. Mars MOLA topography mission identified many crater on Mars surface. Thus despite the Mars dichotomy, both northern and southern hemisphere have been covered by impacts to similar density. Mars currently has no global magnetic field of internal origin. In southern hemisphere, magnetic field intensities due to anomalies of remanent origin are much lower over the gigantic impact craters (e.g. Hellas, Prometheus, and Argyre). Low magnetic field may not relate to the absence of internal dynamo but due to impacts. For example, the aerial survey over a two billion year old, largest crater on Earth, Vredefort in South Africa observed much lower magnetic intensity over the crater, despite of the strongly magnetized simgle domain (SD) magnetite in shocked granites. Randomized magnetic vector orientations caused by impact may be the origin of the lower magnetic field observed on both Vredefort and Mars. We conducted magnetic analysis for a suite of Sierra Madera Impact deformed rock sites with complete shatter cone structures and multiple striated joint set (MSJS), and the initial results were intriguing. NRM vector orientations, REM ratios, and AF demagnetization curves showed contrasted magnetic signatures between the sites as well as within the samples. The NRM signatures in small scale shatter cones and larger scale shatter cones indicated shock demagnetization (SDM). The peculiar signatures of the site with MSJS may be both SDM and shock magnetization (SRM). We characterized the complexity and distinct magnetic signatures of impact fractured rocks. The results suggest that the size of the shatter cones and structures may reflect the magnetic signatures of both intensity and directions. Also, the dimensional scale of shatter cones is indicative parameters for randomization of the magnetic vector orientations. Such variations may influence on overall magnetic intensity observed from a distance, which relates to magnetic anomalies on Mars and Moons.
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 1533 Remagnetization
DE: 1540 Rock and mineral magnetism
DE: 6225 Mars
DE: 6250 Moon (1221)
SC: Planetary Sciences [P]
MN: 2007 Joint Assembly