EVA #4 brought our crew to the Northwest of the habitat, in a region called “Yellow Moon”. The whole region sits between the top member of the Morrison formation (Brushy Basin) and the bottom of Mancos shale, and it is heavily weathered, with soft clay soil. The predominant geological feature of this region is the presence of salts, especially gypsum, from the region of Glistening Seas, through Beige Moon and Grey Moon, all the way to Yellow Moon. Besides samples of crystals, we collected some sandstones with traces of salts.
The different accretion of gypsum crystals, most often occurring in thin layers, and rarely in romboid shape, suggests different water and evaporation processes. The samples will be analyzed in the laboratory, since the short EVA time was just enough for in-situ selection and collection. The area presents outstanding views of the whole region, as described in the EVA report.