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!!