Transcript Mars Magnetic Anomalies

Ester Aranzana
13 de Enero de 2012
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Rock core (Fe-FeS)
No internal magnetic field,
no dynamo action but it
has one in the past
mini-magnetospheres
of crustal origin
Mars Global Surveyor(1996)
- MGS MAG: Magnetic vector
data sparsely from 400-100 km
- MGS ER: scalar field at 180 km
Others: Balloon magnetometer
Rover on Martian surface
Laboratory studies
Magnetic anomalies one order of magnitude higher!!
EARTH
MARS
NASA
Strong magnetization requires
huge volumes (170-190 km
radii, 20-30 km thicknesses)
2 faults
similar to Earth faults with EW trending features
alternating polarity
Plate tectonics era
Connerney et al.
2005
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No magnetic signatures in
basins Hellas, Isydis and
Argyre
=> Shock demagnetization
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No magnetic signature in
volcanoes provinces (Tharsis
& Elysium)=> thermal
demagnetization by
intrusions
Harkani-Hamed 2001
Mini-magnetospheres
above regions with strong magnetized
crust.
Brain et al. 2010
Aurorae at different
latitudes, first
discovered by Mars
Express in 2004 above
Terra Cimmeria (south of
Mars)
ESA
- Cessation of the core field around 4.1 Gyr
By cooling of the planet.
- Origin dichotomy: the new mode is a huge impact
Other explanations: Volcanic features, plate tectonics
- Faults, lineations => Plate tectonics era in presence of a
reversing dynamo
- Internal magnetic field in the past =>The evolution of
climate and habitability in Mars
Roberts et al. 2009
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Connerney, J.E.P, Acuña, M.H. et al. 2005, Tectonic implications of Mars crustal
magnetism, PNAS October 18, 2005 vol. 102 no. 42 14970-14975.
Roberts, J.H., Lillis, R.J., Manga, M. 2009, Giant impacts an Mars cessation of the
Martian dynamo, JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, E04009,
doi:10.1029/2008JE003287, 2009
Jafar Arkani-Hamed 2001, A 50-degree spherical model of the magnetic field of Mars,
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 106, NO.10, PAGES 23,197-23,208.
Purucker, M., Ravat, D., Frey, H., Voorhies, C., Sabaka, T. & Acuña, M. 2000, An
altitude-normalized magnetic map of Mars and its interpretation, GEOPHYSICAL
RESEARCH LETTERS, VOL. 27, NO. 16, PAGES 2449-2452.
Acuña, M. H., Connerney, J.E.P et al. 2001, Magnetic field of Mars: Summary of results
from the aerobraking and mapping orbits, JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 106, NO. E10, PAGES 23,403–23,417
Brain, D.A., Baker, A.H., Briggs, J., Eastwood, J.P., Halekas, J.S. & Phan, T.D. 2010,
Episodic detachment of Martian crustal magnetic fields leading to bulk atmospheric
plasma to escape, GEOPHYSICAL RESEARCH LETTERS, VOL.37, L14108.
Planetary Sciences, Imke de Pater & Jack J. Lissauer, Cambridge University Press 2001.