Simulation of impact melting effect on spectral properties of the Martian surface: Implications for polar deposits

This work explores the hypothesis that meteorite bombardment of polar layer ed deposits could have partially transformed their silicate dust component into sand-sized particles of impact melt glasses and that these particles m ay be a source of the eolian deposits observed in the south polar region by Herkenhoff and Murray [12]. These authors found that the deposits were dar ker and less red in the visible spectrum than the dust. Our experiments sim ulated impact melting of the Martian dust by quick melting of the palagonit e Mars soil analog in a resistance furnace and by pulsed laser irradiation. Spectral reflectance measurements of the produced glasses showed that they were indeed darker and less red in the visible spectrum than the palagonit e analog, which tentatively supports the hypothesis. SEM studies of the gla sses show that melting by laser irradiation (which in terms of duration of melting and quenching is probably closer to the discussed impact melting) p roduced very porous glasses. Sand composed of these glass particles should be even more porous and have a low thermal inertia. These properties make t he material similar. to the dark dunes of the North Polar Erg which have lo w thermal inertia. However, recent HST spectral measurements showed a signi ficant difference in the near-IR spectra between the North Polar Erg dunes and the glasses produced in the laboratory. For the dark material of the so uth polar region, such spectral measurements have not get been performed, t hus leaving more opportunities for thorough testing of the hypothesis for f uture study. Since meteorites globally impact the surface of Mars, we sugge st that impact glasses similar to those produced in our experiments are a s tandard component of Ig dunes and the glasses produced in the laboratory . For the dark material IR spectra between the North Polar E Mars, we suggest tha the Martian ngolith.