MARS-ANALOG ALLUVIAL FANS ALONG THE HILINA PALI, HAWAII

Hesperian to Amazonian-aged alluvial fans may be representative of the last vestiges of widespread water flow on the martian surface, and understanding the environmental conditions present during their formation could yield insights into Mars’ late-stage habitability as it transitioned from a potentially wet and warm early world to the cold and dry Mars we observe today. With the exception of some limited data from the distal portion of the Peace Vallis fan in Gale crater, our understanding of martian fan forming processes comes entirely from orbiter data, which can result in a poor interpretation of deposit types and associated runoff rates and inferred climatic environments.

Here we use remote sensing data combined with fieldwork to describe the geomorphology and interpreted formative sedimentary processes of a series of coarse grained alluvial fans that have formed along the Hilina Pali fault system on the southern side of Island of Hawaiʻi. Hilina Pali is a 500 m fault scarp similar in slope to the interior of an impact crater rim, the preferential location for fan formation on Mars. Sediment is entirely physically weathered basalt. Channels feeding the fans drain the Kaʻū Desert on the leeward side of the Kilauea volcano, and interact with the complex morphology of lava flows and tubes, creating a complicated stratigraphy that is difficult to interpret solely from remote sensing data.

Rather than being formed from classic fluvial or debris flow processes, we interpret the Hilina Pali landforms to be a rare example of fans having formed entirely from sieve lobe deposition. Applying the sieve lobe model to martian fans that were previously identified as debris flow deposits may result in different interpretations of climatic environment. We are currently investigating the rheological properties of these flow events and applying results to a landform evolution model to investigate how fan growth is affected by the rapidly deforming Hilina Pali escarpment and varying sediment supply and basin rock erodibility.