| Summary: | The Hengill volcano area possesses a hydrothermal field with variable surface conditions, covering a pH range of 0.5 to 6.8 and varied redox conditions. High-Fe basalts, similar in composition to the average Martian crust, are thus subjected to a variety of alteration conditions. In 2014, samples were collected from the northern side of this field, along with temperature and pH measurements. Samples include surface samples and samples from depth from soil pits. This is an area of high interest because of its variable composition. Samples from soil pits in the Hengill volcano area show a significant redox gradient with depth. The surface of the soil pits consist of a thin layer of lighter colored, likely more oxidized sulfate minerals, and at 50 cm depth the deposit is a darker grey, likely indicating iron sulfide minerals more consistent with reducing conditions. This varying composition is of great interest for its similarity to a redox gradient observed by the Curiosity rover at Gale Crater on Mars. Microbes can utilize these redox gradients as an energy source, therefore a great analog for a potential habitable environment on Mars. Samples taken from these soil pits will be analyzed by X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD). These methods provide data that can demonstrate changes in geochemistry and mineral assemblages. Mineral assemblages can be determined by XRD and changes in bulk chemistry can be determined by XRF, and these trends can be studied for their association with different conditions when the minerals formed, starting with the same source material available in the Hengill volcano area.
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