37th DPS Meeting, 4-9 September 2005
Session 24 Mars III
Oral, Tuesday, September 6, 2005, 2:00-3:50pm, Music Concert Hall

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[24.04] SPICAM/MEX Discovery of Aurora on Mars

J.L. Bertaux, F. Leblanc (Service d' Aeronomie du CNRS/IPSL,France), O. Witasse (ESA-ESTEC), E. Quemerais (Service d' Aeronomie du CNRS/IPSL,France), J. Lilensten (Laboratoire de Planetologie de Grenoble, France.), S.A. Stern (Southwest Research Institute, Boulder, CO 80302, USA), B. Sandel (Lunar and Planetary Laboratory, Univ.of Arizona, Tucson, AZ 85721, USA), O. Korablev (Space Research Institute (IKI), Moscow, Russia)

In addition to the NO emission detected for the first time in the Night side of Mars, the SPICAM UV spectrometer on board Mars Express has discovered an aurora in the Martian atmosphere (Nature, June 9, 2005). This emission is very localized, found at an altitude around 130 km, over a point of martian coordinates 177 degrees longitude, -52 degrees latitude. This corresponds exactly to a region where the crustal magnetic field is maximum, according to previous MGS mapping of the martian magnetic field, which is a remnant of an ancient intrinsic magnetic field now extinct.

The main emissions in the auroral spectrum are: 1) the CO Cameron band between 180 and 240 nm (694 ± 50 Rayleighs), also observed on the dayside . 2) the CO2+ doublet at 289 nm (71 ± 42 Rayleighs). 3) possibly fainter emissions from CO Fourth Positive Group between 135 and 170 nm and O at 297.2 nm. The presence of such emissions in the night therefore indicates excitation of the Martian atmosphere by a flux of particles, probably electrons, along magnetic field lines connected to the ground and to the interplanetary field. A new analysis of the photometry of three low resolution spectra will be presented, yielding more accurate intensity determinations.

We wish to thank CNRS and CNES for financing SPICAM in France, the Belgian government, the Russian Academy of Sciences and NASA for support of US co-investigators.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.