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Mars Magnetic Anomalies

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)

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Mars Magnetic Anomalies

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  1. Ester Aranzana 13 de Enero de 2012 Mars Magnetic Anomalies

  2. Introduction • Rock core (Fe-FeS) • No internal magnetic field, no dynamo action butit has one in the past mini-magnetospheres of crustal origin

  3. 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

  4. Results Magnetic anomalies one order of magnitude higher!! EARTH MARS NASA

  5. 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 Plate tectonics era Connerney et al. 2005

  6. 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

  7. Results 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

  8. Discussion - 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

  9. 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 • JafarArkani-Hamed 2001, A 50-degree spherical model of the magneticfield 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-normalizedmagneticmap of Mars and itsinterpretation, GEOPHYSICAL RESEARCH LETTERS, VOL. 27, NO. 16, PAGES 2449-2452. • Acuña, M. H., Connerney, J.E.P et al. 2001, Magneticfield of Mars: Summary of resultsfrom the aerobraking and mappingorbits, 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, Episodicdetachment of Martiancrustalmagneticfieldsleading to bulkatmospheric plasma to escape, GEOPHYSICAL RESEARCH LETTERS, VOL.37, L14108. • Planetary Sciences, Imke de Pater & Jack J. Lissauer, Cambridge UniversityPress 2001.

  10. THANKS Thank you!!

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