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Ester Aranzana 13 de Enero de 2012. Mars Magnetic Anomalies. Introduction. Rock core (Fe- FeS ) No internal magnetic field, no dynamo action but it has one in the past. mini-magnetospheres of crustal origin . Observations. Mars Global Surveyor(1996) - PowerPoint PPT Presentation
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Mars Magnetic Anomalies
Ester Aranzana13 de Enero de 2012
Introduction
Rock core (Fe-FeS) No internal magnetic
field, no dynamo action but it has one in the past
mini-magnetospheres of crustal origin
Observations
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
Results
EARTH MARS
NASA
Magnetic anomalies one order of magnitude higher!!
Plate tectonics era
Results: Dichotomy
Strong magnetization requires huge volumes (170-190 km radii, 20-30 km thicknesses)
2 faults similar to Earth faults with E-W trending features alternating polarity
Connerney et al. 2005
Results No magnetic signatures
in basins Hellas, Isydis and Argyre
=> Shock demagnetization
No magnetic signature in volcanoes provinces (Tharsis & Elysium)=> thermal demagnetization by intrusions
Harkani-Hamed 2001
Results
Mini-magnetospheresabove 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
Discussion- Cessation of the core field around 4.1 Gyr By cooling of the planet.
- Faults, lineations => Plate tectonics era in presence of a reversing dynamo
- Origin dichotomy: the new mode is a huge impact Other explanations: Volcanic features, plate tectonics
Roberts et al. 2009
- Internal magnetic field in the past =>The evolution of climate and habitability in Mars
REFERENCES 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.
THANKS
Thank you!!