VNIR Spectra of Glass Atop the Holuhraun Lava Flow Field as an Aqueous Martian Analogue

The 2014-2015 Holuhraun lava flow field in Iceland was emplaced into a water-rich environment of falling snow, rain, and an active glacial outwash plain. Despite the presence of water, there is a lack of prominent explosive eruption features common with water-rich emplacement, making Holuhraun a unique Martian analogue to understand the morphologic and spectral characteristics produced by moderate lava-water interaction. The flow field ranges in various morphologies and roughnesses (aa vs pahoehoe) attributed to differences in local emplacement styles (negative terrain, abundance of water) and volcanic history (eruption frequency and area). Upon moderate contact with water or ice, basaltic flows such as Holuhraun rapidly quench forming a noncrystalline glassy surface distinct from the surrounding basalt. Glass-rich materials can be measured in VNIR spectra as overall reflectance based on the proportion of glass and crystals in the flow field surface. Thus, glass content variations may correlate to the cooling and emplacement styles of Holuhraun for applications to extraterrestrial flows. However, other variations such as surface roughness and chemical composition may also affect overall reflectance. In this study, we use WorldView-3 and AVIRIS data to compile VNIR spectral data 500-1000nm to create an averaged reflectance map of Holuhraun. Spectral absorptions within this range follow terrestrial VNIR classifications by their overall 300-2500nm absorbance features of glass-, olivine-, plagioclase-, and alteration-rich spectra. We investigate glass content across the flow and consider other factors which may interfere with the absorptions of glass. These images can supplement terrestrial observations with future in-situ VNIR field measurements to validate our spectral interpretations. The spectra observed between datasets can then be applied to extraterrestrial environments, such as Mars, where remotely sensed VNIR data are available but field sampling is limited.