Exploring the Mars' surface composition with the PFS instrument, and the bed special library

Abstract

The Planetary Fourier Experiment (PFS) on board the ESA Mars Express mission is routinely observing the red planet since the beginning of 2004, and collected more than one million Mar- tian spectra. The spectrometer measures the radiation emerging from the planet simultaneously in the Long Wavelength Channel (LWC) between 5 and 45 µm, and in the Short Wavelength Channel (SWC), in the 1 to 5 µm spectral intervals. The Berlin Emissivity Database (BED) is a spectral library containing true emissivity measurements of planetary analogues, covering the whole 3 to 50 µm spectral range in four grain size separates: 0-25, 25-63, 63-125, 125-250 µm, to efficaciously represent the variety of grain sizes composition of a typical planetary surface. By means of a principal component (factor) analysis and a target transformation technique, we separated the atmospheric from the pure superficial contribution to the calibrated PFS LWC spectra. The surface emissivity spectrum was modelled with a linear deconvolution algorithm, using the BED entries as endmembers. Among the investigated Martian regions, are Syrtis Major and Mawrth Vallis, where the phyllosilicates detection from other remote sensing instru- ments (Omega on Mars Express and CRISM on the NASA Mars Reconnaissance Orbiter) were confirmed and better characterized in terms of singular mineral abundances. The study carried on shows that having multiple grain sizes endmembers in the used spectral library, significantly increases the accuracy of the results.