Ester Aranzana 13 de Enero de 2012 Introduction Rock core Fe FeS No internal magnetic field no dynamo action but it has one in the past minimagnetospheres of crustal origin Observations ID: 462292
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Slide1
Mars Magnetic Anomalies
Ester Aranzana
13 de
Enero
de 2012Slide2
IntroductionRock core (Fe-FeS
)No internal magnetic field, no dynamo action but it has one in the past
mini-magnetospheres of crustal origin Slide3
ObservationsMars 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 studiesSlide4
Results
EARTH
MARS
NASA
Magnetic anomalies one order of magnitude higher!! Slide5
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. 2005Slide6
ResultsNo magnetic signatures in basins Hellas,
Isydis and Argyre => Shock demagnetization
No magnetic signature in volcanoes provinces (
T
harsis
& Elysium)=>
thermal demagnetization
by intrusions
Harkani-Hamed
2001Slide7
ResultsMini-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)
ESASlide8
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 MarsSlide9
REFERENCESConnerney,
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.Slide10
THANKS
Thank you!!