Geological reconnaissance was conducted on EVA 7 in conjunction with the biological sampling.

Lithological units which had been mapped with Landsat 7 multispectral data in Candor Chasma were visited and identified. Due to limited time on site, and the geomorphology of the canyon, the observation of higher stratigraphic units was hindered and only two main lithologies were identified and described.

The first unit, seen in a cliff exposure of approximately 15m thickness (WGS84, UTM 12S 520375 4251031) was dominated by massive sandstone beds interbedded with alternating strata of oxidized and reduced shale. Large scale cross-bedding was noted in some sandstone beds, although most were massive.

The second unit (WGS84, UTM 12S 520703 4251108), which stratigraphically underlies the first, is dominated by oxidized shales, and contains occasional reduced shale, sandstone, and possible carbonate beds between 10 and 30 cm thickness. The basal portion of this unit displays extensive calcite (CaCO3) veining. The calcite source is local in origin.

Boudinage structure was also observed in the second unit, with either sandstone or carbonate beds acting as the competent horizons. This structural deformation points toward lateral extension.

Note: Due to the physical restrictions imposed by the space suits, and the steep nature of the canyon walls, many portions of the lithological units were not directly accessible, and were assessed at a distance.