1. Ester Aranzana 13 de Enero de 2012

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

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

5. Plate tectonics era 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

6.  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. 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. - 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

9.  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.

10. Thank you!!