Aeolian Activity on Pavonis Mons. Persistent aeolian activity was observed on the flanks of the three large Tharsis volcanoes. The dark albedo ring was especially well-developed on Pavonis Mons, as seen here, where it was 20 km wide and situated at altitudes between 20 and 25 km. The boundaries of the dark albedo ring are ragged, and the upper boundary is composed partly of coalescing, ragged dark streaks trending downhill. The image is about 200 km across.
North is to the upper left.
Another view shows the same area taken after the 1977 global dust storm. The observed changes are best explained by the erosion by downslope winds of bright albedo material-probably storm fallout. Aeolian activity has been observed up to the summits of the Tharsis volcanoes, proving that Martian winds are strong enough to transport fine particles even at the very low pressures at the tops of the Tharsis volcanoes. The image is about 700 km across. North is to the upper right.