MARS EXPLORATION ROVER GEOLOGIC TRAVERSE SCIENCE IN THE GUSEV PLAINS

Spirit (MERA) executed the first systematic geologic transect on another planet during its 2.5 km traverse from across the Gusev plains of Mars from the landing site to the Columbia Hills. The traverse successfully tested the ability to apply the techniques of field geology by remote rover operations, and for the first time in the history of Mars exploration field-tested maps prepared from orbital data by actual field geologic traverse on the surface. Using a transect approach to the traverse, a systematic series of overlapping panorama, remote sensing observations, surface analyses, and three trenching operations documented differences in surficial geology and soil chemistry along a 40 meter-wide corridor along the traverse.

Geologic contacts crossed included ejecta blankets from larger impact craters and the regional contact between the lava plains and the Columbia Hills. Traverse observations confirmed that orbital mapping successfully identifies the principal contact relations in high resolution image data, while also proving some insight into the details of local geologic surfaces processes and structures. Rover position data documented relief associated with impact craters, the local relief on the general plains surface, and an approximate 20 m regional ascent in relief from the landing site to the base of the Columbia Hills. Areas of local relief tend to be rougher and blockier, whereas topographic lows are relatively smooth. Vesicularity of rocks in the plains lava surface varied with host rock dimension and angularity. The population of vesicular are interpreted to imply a relatively thin upper vesicular zone for the plains lavas. The successful demonstration of the transect method with a rover while crossing the plains of Gusev crater implies that future rover missions of extended distance and duration will benefit from a similar systematic observation plan.