Applying portable Raman spectrometers for field discrimination of sulfates: Training for successful extraterrestrial detection
Abstract
The presence of sulfates containingMg, Fe, and Ca (in several hydration states) has been confirmed on Mars fromdata acquired by both orbital and in-situ measurements. It has been suggested that the sulfates on Mars originated deep the past from the evaporation of water at accumulation points on the Martian surface.
Consequently, they can be seen as highly relevant to any search for the presence of extraterrestrial life. Miniaturized Raman spectrometers (which permit analysis of the mineralogical and molecular composition of a specimen) will be included in rovers on future planetary exploration missions.
Portable miniature Raman spectrometers operating in the near-infrared (785 nm) and in the green (532 nm, currently selected for the ExoMars mission) were used on-site to estimate the mineralogical compositions of sulfate weathering crusts at Valachov (Bohemian Massif, Czech Republic). Spectra of sufficient quality were quickly obtained, and the characteristic shifts of the sulfate v(1) band of the minerals allowed for the discrimination of several sulfates.
Superficial crusts contained gypsum, jarosite, rozenite, fibroferrite, magnesiocopiapite, and melanterite as major components. The current testing has confirmed the favorable performance of handheld instruments for the discrimination of structurally similar sulfates of relevance for studies on Mars.