MAGNETIC HISTORY OF THE MOON AND MARS

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MAGNETIC HISTORY OF THE MOON AND MARS
Stan Cisowski and Mike Fuller, HIGP-SOEST, Univer
sity of Hawaii, Honolulu, Hawaii.
Research topic for fun - essentially talk given
at AGU December 2003
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Observations
Moon Site magnetometer surveys Sub-satellite
magnetometers surveys Satellite surveys - Lunar
prospector Electron reflectance experiment
Apollo returned samples Lunar meteorites
Mars Satellite magnetometer surveys Electron
reflectance experiment Martian meteorites
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Apollo Magnetometer Site Surveys
Dyall, Parkin and Sonnett, 1970
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Sub-satellite magnetometer surveys
Coleman et al., 1973
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Reiner Gamma type swirls
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Apollo Returned samples - mare basalts, breccia
and soil
Rock magnetism
Paleomagnetism
Implications for Lunar magnetism
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Rock magnetism

1. Fe in basalt,
2. FeNi Melt breccia and
3. Superparamagetic Fe in Soil

Nagata et al., 1972
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Mare basalts
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Melt breccias
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Regolith Breccias
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Shock Magnetization and Demagnetization
Cisowski et al., 1973
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More Shock Effects
Cisowski et al., 1973
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17km/s Flying plate impact into basalt (Srnka et
al., 1979)
Shock Magnetization Impact Induced
Field changes
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Lunar Basalts Paleointensity Summary
Cisowski and Fuller, 1986
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Lunar paleointensity Linear f(t)
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Lunar Paleointensity log f(t)
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Abundance and Distribution of Iron on the
MoonLucey, Taylor and Malaret (1995)
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On to Mars.
Martian meteorites
Viking - soil analysis Crustal anomaly model
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Paleomagnetism of ALH84001
High resolution SQUID observations
Weiss et al., 2002
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Fine magnetite in carbonate
Magnetite in Martian meteorite ALH84001
Transmission electron microscope image showing
oriented elongated magnetites (M) and regions
containing periclase (P) in carbonate in ALH84001
(Barber and Scott, 2002).
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Paleomagnetism of ALH84001
Soft -reversed
Soft magnetization
Hard magnetization
AF Demagnetization of NRM
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AF DEMAGNETIZATIONCHARACTERISTICS
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Demagnetization of IRMs
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Mars Crustal Magnetic Anomalies
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Comparison between
Comparison between terrestrial and martian
crustal anomalies
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Models for Martian Crustal Magnetic Anomalies
Magnitude and Occurrence
Sea floor spreading (Connerney et al,1999),
Terrane accretion (Fairen et al, 2001) Igneous
model (Hammer and Brachfield 2003) Hydrothermal
alteration of igneous rocks (Harrison 2001,
Solomon et al., 2003)
Magnetic phases invoked Magnetite,
Pyrrhotite, Hematites, Hemo-ilmenties, Maghemite
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Magnetization of Martian Crust
Modeling suggests crust locally magnetized in
southern hemisphere to 20 km with intensity
10 A m-1 (Connerney, Nimmo, Parker).
Intensity of magnetization acquired by rocks
depends on 1. Magnitude of Martian field. 2.
Mechanism of magnetization. 3. Magnetic
material
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Outline of Model
In southern highlands
When dense CO2 atmosphere present and water is
stable, weak acid forms and Fe-rich carbonate
deposited in crust. Continued growth of crust
from magmatic intrusions causes siderite
decomposition forming single-domain magnetite.
Locally 1 carbonate forms to depth of 20
km and is converted to 0.5 SD magnetite. Earth-l
ike field from dynamo induces intensity of
magnetization of up to 10 A m-1 prior to 4.0
Gyr. SD magnetite stable over 4 Gyr due to
subsequent lack of water, as in ALH84001.
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Suggested Origin of Single-Domain Magnetite in
Martian crust during Noachian (Hydrology after
Clifford Parker 2001)