AN INVESTIGATION INTO THE EFFECTIVENESS OF MARS ROVER TECHNIQUES IN IDENTIFYING SOURCE-TO-SINK SEDIMENTARY PROCESSES IN BASALTIC ENVIRONMENTS

Fieldwork on Mars largely consists of a combination of rover-based imaging techniques and geochemical analyses (e.g., XRF, LIBS, etc.). Several studies have used these methods to interpret source-to-sink processes that formed sedimentary rocks on Mars; however, limited terrestrial investigations of sediments in basaltic environments have been conducted using the same methods. Therefore, there is a need to test the effectiveness of these rover-analog analytical methods at disentangling the respective signatures of source compositions and sedimentary processes.

We investigate 10 km of a glacio-fluvio-aeolian sedimentary system and its source rocks at the Þórisjökull area in SW Iceland within the SAND-E: Semi-Autonomous Navigation for Detrital Environments rover simulation. SAND-E analyzed, sampled, and documented the sediments using ground-based and aerial images and XRF spectroscopy techniques at three field sites proximal, medial, and distal to the sediment source. Samples of the subglacially erupted and subaerially erupted volcanoes situated in the sediment catchment were also collected and analyzed using the same methods to permit a direct comparison to the sediments.

Results of the source rocks show that the subglacial volcanoes contain both olivine-phyric and plagioclase-phyric crystalline lava, and tuff composed of brecciated pillow lava, glass, and palagonite. In contrast, the subaerial volcano is plagioclase-phyric. Sediments at the proximal site are the most geochemically and visually diverse. Both fluvial and aeolian sediments at the distal site are relatively more uniform in composition and show an increase in MgO away from the plagioclase-phyric endmembers towards the olivine-phyric endmember. Images of the sand and pebbles show a greater abundance of crystalline grains relative to glassy grains at the distal site with less grain size variation suggesting that physical grain sorting is influencing the geochemical change. Our results show that rover-based techniques are able to identify variations in the sediments relative to physical and chemical weathering of different basaltic source rocks, with bulk-XRF data providing an average composition for the sand and mud grains that is not indicative of a single source, but rather indicates mixing between them and subsequent sorting.