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