1 U.S. Geological Survey, MS964 Box 25046 DFC, Denver, C olorado 80225; gswayze@speclab.cr.usgs.gov 2 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109 3 Vector Engineering, Inc., 12438 Loma Rica Drive, Suite C, Grass Valley, California 95945 4 Previously at the U.S. Geological Survey, Kilauea Volcanic Observatory, Hawaii Figure 1. Growth stages of the Big Island shield volcanos. 1 Mineral Mapping Mauna Kea and Mauna Loa Shield Volcanos on Hawaii Using AVIRIS Data and the USGS Tetracorder Spectral Identification System: Lessons Applicable to the Search for Relict Martian Hydrothermal Systems Gregg A. Swayz e, 1 Roger N. Clar k, 1 Stephen J. Sutle y, 1 Carol A. Gent, 1 Barnaby W. Rockwel l, 1 Diana L. Blane y, 2 James L. Post, 3 and Brian P. Farm 4 INTRODUCTION The Hawaiian AVIRIS campaign conducted during the spring of 2000 provided an opportunity to collect hyperspectral data over a unique geologic environment on the sides of two of the Earth’s largest shield volcanos. High altitude AVIRIS data were collected on April 14, 2000 along a 75 km NE traverse passing over the summits of Mauna Kea (4205 m) and Mauna Loa (4064 m) encompassing the saddle (1940 m) between them. This traverse covers diverse climatic and ecological zones extending from tropical coastal forests to alpine tundra over an elevation range of 3200 m. The summits of both volcanos are among the highest and driest readily accessible areas in the world with the summit of Mauna Kea chosen as the site for the largest collection of telescopic observatories in the world. In the cool-dry atmosphere atop these shield volcanos, rocks are nearly devoid of macroscopic life and chemical weathering is relatively low. These extreme climatic conditions and extensive basalt outcrops combine to form one of the best terrestrial analogues to the Martian shield volcanos. Several studies have suggested that certain palagonitic soils from Mauna Kea are good spectral analogues of Martian surface materials (Singer et al., 1979, Singer, 1982; Evans and Adams, 1979, 1980; Allen et al., 1981, 1982). Other studies suggest that hydrothermal systems may have been sanctuaries for ancient life on Mars (Walter et al., 1993; Farmer and DeMarais, 1994; Wade et al., 1999). Examples of relict hydrothermal systems exist at the summits of both Mauna Kea and Mauna Loa, and these areas were measured by AVIRIS as terrestrial analogues of the mineral associations and spatial extent of hydrothermal systems developed in mafic volcanic rocks. VOLCANIC HISTORY OF THE BIG ISLAND There are five distinct volcanos that grew and merged to form the Big Island of Hawaii. The loci of volcanism (Fig. 1) has shifted progressively southeastward over time reflecting the NW motion of the Pacific plate over the Hawaiian hot spot (Clague and Dalrymple, 1987). The most intense subaerial volcanic activity is now centered at the two southernmost volcanos, Mauna Loa and Kilauea. The youngest and smallest volcano in the Hawaiian chain is Loihi which is growing beneath the sea 30 km SE of the Big Island (Wolfe and Morris, 1996 and references therein). Ideally a Hawaiian shield volcano goes through four stages during it life: preshield, shield, postshield, and rejuvenation (Clague and Dalrymple, 1987, 1989). Accordingly, the preshield stage involves initial eruption of alkalic basalt, followed by the shield building stage eruption of tholeiitic basalts (low in alkalis), which eventually gives way to the postshield stage eruption of more SiO 2 -rich alkali hawaiite lavas. The rejuvenated stage involves the eruption of SiO 2 -poor lava after a few million years