¹F. Zambon,¹C. Carli,²J. Wright,²D. A. Rothery,¹F. Altieri,^3,4M. Massironi, F. Capaccioni,⁴G. Cremonese
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2021JE006918]
¹INAF-Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100 I-00 133 Rome
²The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
³University of Padua, Department of Geoscience, Via Gradenigo 6, I-35 131 Padua Italy
⁴INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio, 5, 35 122 Padua Italy
Published by arrangement with John Wiley & Sons

MESSENGER mission data allowed the entire surface of Mercury to be mapped at various spatial scales, from both geological and compositional stand points. Here, we present a spectral analysis of the H05-Hokusai quadrangle, using data acquired by the Mercury Dual Imaging System-Wide-Angle Camera. We defined a suitable set of parameters, such as reflectance and spectral slopes, to study the spectral variation though the definition of spectral units. The determination of spectral units permits to infer the physical and compositional properties of a surface by processing several parameters simultaneously, instead of the more traditional approach of interpreting each single parameter separately. We identified 11 spectral units within H05, 6 large scale and 5 localized units. The large scale units include the northern smooth plains of Borealis Planitia. South-western H05 is characterized by two widespread spectral units, partially overlapping intercrater plains and intermediate plains. Furthermore, we found very localized spectral units corresponding to the low-reflectance blue material of Rachmaninoff basin and the high-reflectance red material of Nathair Facula. We investigated the link between spectral units and compositional maps obtained by GRS and XRS, to associate compositional information to the spectral units. We found some spectral units are correlated with Mg and Al variations displayed in the elemental maps. This implies that spectral variations associated to these units are mainly linked with composition rather than terrain maturity and/or grain size effects.

¹John O.Edgar,²Katie Gilmour,²Maggie L.White,¹Geoffrey D.Abbott,¹Jon Telling
Earth and Planetary Science Letters 579, 117361 Link to Article [https://doi.org/10.1016/j.epsl.2021.117361]
¹School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
²School of Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
Copyright Elsevier

The surface of Mars is a dynamic, cold environment where aeolian abrasion leads to the fracturing of silicate minerals which can produce oxidants upon exposure to water. Here we report results of a series of laboratory experiments where the abrasion of sand sized (125 – 300 μm) quartz, labradorite, forsterite and opal were conducted under a simulated Martian atmosphere at a range of temperatures common to Mars’ surface (193 to 273 K). Our results suggest that abrasion rates are controlled by temperature; an observation that may have potential for providing insight into Martian paleo-temperatures. On the addition of water, detectable H2O2 was generated in all abraded experiments with crystalline quartz, labradorite and forsterite, but not amorphous opal – supporting previous inferences that mineral crystal structure plays a role in oxidant production. Dissolved Fe concentrations also indicated a strong additional control on net H2O2 production by Fenton reactions. Detectable H2 was similarly measured in abraded experiments with crystalline minerals and not for amorphous opal. Labradorite and forsterite generated minimal H2 and only in more abraded samples, likely due to the reaction of Si• with water. In quartz experiments H2 was only present in samples where a black magnetic trace mineral was also present, and where H2O2 concentrations had been reduced to close to detection. In the quartz samples we infer a mechanism of H2 generation via the previously proposed model of spinel-surface-promoted-electron transfer to water. The presence of H2O2 may exert an additional control on net H2 production rates either directly (via reaction of H2 with OH• and H2O2) or indirectly (by the oxidation of H2 generating sites on mineral surfaces). Overall, our data supports previous inferences that aeolian abrasion can produce additional oxidants within the Martian regolith that can increase the degradation of organic molecules. We further suggest that the apparent control of H2O2 concentrations on net H2 generation in our experiments may help explain some previous apparently contradictory evidence for mineral-water H2 generation at low temperatures.