Spectral and petrologic analyses of basaltic sands in Ka'u Desert (Hawaii) – implications for the dark dunes on Mars

Abstract

Dark aeolian deposits on Mars are thought to consist of volcanic materials due to their mineral assemblages, which are common to basalts. However, the sediment source is still debated. Basaltic dunes on Earth are promising analogs for providing further insights into the assumed basaltic sand dunes on Mars. In our study we characterize basaltic dunes from the Ka'u Desert in Hawaii using optical microscopes, electron microprobe, and spectral analyses. We compare the spectra of terrestrial and Martian dune sands to determine possible origins of the Martian dark sediments. Our results show that the terrestrial sands consist primarily of medium to coarse sand-sized volcanic glass and rock fragments as well as olivine, pyroxene, and plagioclase minerals. Grain shapes range from angular to subrounded. The sample composition indicates that the material was derived from phreatomagmatic eruptions partially with additional proportions of rock fragments from local lava flows. Grain shape and size indicate the materials were transported by aeolian processes rather than by fluvial processes. Spectral analyses reveal an initial hydration of all terrestrial samples. A spectral mineralogical correlation between the terrestrial and Martian aeolian sands shows a similarity consistent with an origin from volcanic ash and lava. We suggest that the Martian deposits may contain similar abundances of volcanic glass, which has not yet been distinguished in Martian spectral data.

Interpretation of the complex dune morphology on Mars: dune activity, modelling and a terrestrial analogue

“…The draa 0339–488 covers an area of 180 km 2 . It consists of optically dark, presumably basaltic sand (Tirsch et al ., ) and reaches a maximum elevation of ~450 m above the crater floor (Figure ). A volume of ~13 km 3 was estimated for this draa (see the documentation ‘Field Description and Details for Dune_Field layer’ in the Mars Digital Dune Database – MGD 3 , Hayward et al ., ).…”

Recent developments in planetary Aeolian studies and their terrestrial analogs

“…Large craters that formed in the later Hesperian-Amazonian eras exposed the volcanic ash and subsequent smaller impacts continued release sediments for Aeolian transport. Both spectral and petrologic studies of basaltic sands from the Ka'u Desert in Hawaii suggest that the dark dunes on Mars may be reconcilable with the abundance of basaltic volcanism across Mars without requiring unique mono-mineralic sources that otherwise might be difficult to justify or explain (Tirsch et al, 2012). The dune compositions are a distinct contrast from hydrated silicate minerals ) and the very limited exposures of carbonate rocks (Ehlmann et al, 2008) observed elsewhere in spectral data of Mars, aided in part by the typically strong albedo contrast between Martian dunes and their dusty surroundings.…”

Planetary dune analogues: a special issue on integrating models, remote sensing and field data

“…Selecting sites with repeated passes of Mars Reconnaissance Orbiter (MRO), as well as those HiRISE scenes that offered high contrast between substrate and dark dune sands, has allowed for sand transport to be identified by scene subtraction between the image pairs within a GIS. These results are significant additions to the understanding of aeolian transport pathways for Mars and offer data that can be compared with terrestrial analogues in which direct analysis of source-to-sink settings are made (see, for example, in this Special Issue: Hooper et al, 2012;Tirsch et al, 2012). Significantly, layered sediments within the walls of two of the three intra-crater settings are likely sand sources.…”