"Erosion and Modification of the Keanakako’i Tephra in Hawaii: Clues For Understanding Early Mars"

A variety of geologic evidence indicates that the surface of Mars is composed primarily of basalt. Based on our understanding of impact crater formation and numerical simulations of volcanic eruptions under low atmospheric pressures, it is likely that the martian surface is brecciated to considerable depths, too. The Ka'u Desert represents a unique environment where the effects of erosion and weathering of basaltic materials, similar to those found Mars, can be investigated. The Ka'u Desert is located on the western flank of Kilauea where trade winds blow volcanic gases, such as sulfur dioxide, downwind resulting an acidic environment that is too harsh to support vegetation. Centuries of explosive eruptions at Kilauea have deposited a thick layer of basaltic ash and tephra that spread approximately 10-15 km (6-10 miles) into the desert. Known as the Keanakako'i Formation, this material is subjected to periodic storms that erode the deposit and transport the sediments into the desert where the trade winds subsequently blow these materials towards the ocean. The goals of our studies are to (1) determine the climatic conditions necessary to generate runoff and erosion on the Keanakako'i and (2) examine how the physical and chemical characteristics of these materials change with transport process and distance. I will also discuss the current explosive eruptions at Kilauea, which offer a rare opportunity to understand how the physical and chemical characteristics of the Keanakako'i change as a function of distance during the actual deposition process. Analyses of these latest deposits will provide an important baseline for our analyses. Results from our study will eventually lead to a better understanding of the early martian climate, and perhaps the types of storms that may have been present. We will also gain a better understanding of soil formation on Mars and perhaps develop new methods for estimating the maturity of martian surface materials.