La cité américaine au Champ-de-Mars [soldats américains sous une tente avec des lits] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 52992

[20 phot. de l'Andalousie après le tremblement de terre de la fin de 1884, provenant de la mission française dirigée par F. Fouqué. Voir l'article de ce dernier dans le n°311, du 14 mars 1886, du Bulletin hebdomadaire de l'Association scientifique de France. Don Fouqué en 1886]

Donateur : Fouqué, Ferdinand (1828-1904)

Déléguées des groupements féminins à la conférence de paix [à Paris, le 18 mars 1919, au ministère du Travail] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 52998

The chemical variability at the surface of Mars: implications for exogenic processes

The chemical composition of sediments and rocks, as well as their distribution at theMartian surface, represent a long term archive of processes, which have formed theplanetary surface. A survey of chemical compositions by means of Compositional DataAnalysis represents a valuable tool to extract direct evidence for weathering processesand allows to quantify weathering and sedimentation rates. clr-biplot techniques areapplied for visualization of chemical relationships across the surface (“chemical maps”).The variability among individual suites of data is further analyzed by means of clr-PCA,in order to extract chemical alteration vectors between fresh rocks and their crusts andfor an assessment of different source reservoirs accessible to soil formation. Bothtechniques are applied to elucidate the influence of remote weathering by combinedanalysis of several soil forming branches. Vector analysis in the Simplex provides theopportunity to study atmosphere surface interactions, including the role andcomposition of volcanic gases