An Analogy Study of Basaltic Dune Sands on Mars and Earth

Kurzfassung

Dark aeolian bedforms 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 and needs further affirmation. Basaltic dunes on Earth are rare and can only be found in a few places including New Zealand, Iceland, the western USA, Peru, and Hawaii. These dunes composed of volcaniclastic sediments are promising analogues for providing further insights into the assumed basaltic sand dunes on Mars. In our study we use basaltic dunes sands collected in Hawaii’s Ka’u Desert, which are especially interesting for addressing the source of Martian dunes because of the co-occurrence of active volcanic processes and dune development. For these dunes we could prove that their material has been derived from airfall ashes from phreatomagmatic eruptions of Kilaulea and reworked lava. Basaltic dunes sand from Arizona builds a second set of terrestrial analogue samples in our study. These sands have been collected from aeolian bedforms that are composed of reworked volcanic ash erupted from nearby sinter cones. Spectral analyses of the terrestrial samples show that the dune sands are enriched in pyroxene and olivine, a basaltic composition similar to that of the Martian dark dunes. Microprobe analyses show that the terrestrial sands are dominated by olivine, pyroxene, plagioclase, and glasses resulting from the volcanic source of these aeolian sediments. This result is consistent with modal mineralogy modeling of Martian dunes sands. These correlations prove the hypothesis of a similar origin of the Martian and terrestrial dune sands consistent with reworked volcanic ash and lava.