Accueil > Séminaires d’Astrophysique > Automne 2006 > Chemistry of the Martian surface : Recent results of APXS measurements onboard the Mars Exploration Rovers

 

Chemistry of the Martian surface : Recent results of APXS measurements onboard the Mars Exploration Rovers

Johannes Brückner (Max Planck Institute für Chemie de Mayence, Allemagne)

Par Stephane Charpinet - 8/01/2007

 

Séminaires d’Astrophysique

de l’Observatoire Midi-Pyrénées


Séminaire de

Johannes BRÜCKNER

 (Max Planck Institute for Nuclear Physics, Heidelberg, Allemagne)


Jeudi 12 Octobre 2006 à 11h

CESR


Chemistry of the Martian surface : Recent results of APXS measurements onboard the Mars Exploration Rovers

In January 2004, the two Mars Exploration Rovers (MER) landed at two different sites, Gusev Crater and Meridianum Planum, 180 degrees apart on Mars. Remarkably, the two rovers have been working in the harsh martian environment until today. The Alpha Particle X-Ray Spectrometers (APXS) onboard the two rovers determine the elemental compositions of martian samples. APXS measurements are performed by placing the sensor head immediately above the sample surface. Concentrations of major and minor elements are obtained from these measurements. For the first time, in situ detection of trace elements such as nickel, zinc, and bromine could be performed. A wealth of compositional diversity has been discovered at the two MER landing sites. At Gusev Crater, fresh rock surfaces in the plains resemble primitive basalts, while rocks in the Columbia Hills are significantly weathered and enriched in mobile elements, such as phosphorus, sulfur, chlorine, and bromine. At Meridiani Planum, the layered sediments were found to consist primarily of sulfates mixed with siliciclastic debris. Iron-rich spherules and their fragments are found armoring the top-most soil layers as well as embedded in the outcrop rocks. A variety of erratics, including an iron-nickel meteorite and a likely ejecta fragment similar to martian meteorites, have also been discovered. The elemental compositions of soils analyzed at both landing sites are remarkably similar, indicative of global-scale homogenization. Together with results from other instruments onboard the rovers evidence was found that aqueous activities occurred on the sites probably in an ancient epoch, but not necessarily in recent times.

 

 

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