mars magnetic anomalies
DESCRIPTION
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 PresentationTRANSCRIPT
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Mars Magnetic Anomalies
Ester Aranzana13 de Enero de 2012
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Introduction
Rock core (Fe-FeS) No internal magnetic
field, no dynamo action but it has one in the past
mini-magnetospheres of crustal origin
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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
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Results
EARTH MARS
NASA
Magnetic anomalies one order of magnitude higher!!
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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
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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
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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
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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
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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.
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THANKS
Thank you!!