The photograph in figure 25-59 and the corresponding map (fig. 25-60) show the geology of part of the lunar surface just east of the Littrow rilles at the eastern edge of Mare Serenitatis. The most striking feature of the region is the extremely low albedo of the area mapped as Eld in the western half of the map. The low albedo is believed to be caused by a thin layer of pyroclastic volcanic material at the surface. Another notable feature is the fresh-appearing ridges that cross the mare and the adjacent terra. The fine-braided texture of these ridges contrasts markedly with the rounded, subdued topography more common to such features, an indication that the ridges here may be unusually young. Also evident is a well-exposed succession of marelike plains units, which probably represent different stages in the filling of the Serenitatis basin. Several sets of rilles are present; most are roughly tangential to the basin and terminate against the different plains units according to the relative ages. In the northwest corner of the map is a relatively fresh volcanic crater chain (Cch) from which material appears to have been ejected over the surrounding terrain, forming rays of volcanic ejecta. The area thus includes an unusually wide variety of lunar features.
