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Crater rays are formed during a cratering event as target material is ballistically ejected to distances of many crater radii forming narrow, generally high albedo, approximately linear features extending outward from the crater. The nature of crater rays was examined for the lunar crater Copernicus using new information on, the composition of surface material (from near-IR reflectance measurements), surface roughness (from radar backscatter measurements), and photogeologic data (from available images). Part of the data analysis included use of mixing models to quantify the mixing systematics observed between primary ejecta and local substrate of the ray on the basis of compositional parameters from reflectance spectra. Primary material from Copernicus can be detected in the surface material of rays in decreasing amounts with increasing radial distance (e.g., 20-25% primary ejecta at six crater radii). For distances greater than three crater radii the proportion of local material to primary ejecta observed from these compositional reflectance data is approximately equal to that predicted by previous laboratory and ballistic studies of craters. Within three crater radii the compositional data indicate a higher proportion of primary ejecta than predicted. For extended areas along the ray that do not contain large secondary craters the primary ejecta is intimately mixed on the granular scale with local material throughout the regolith. The relatively high albedo of the rays of Copernicus is due to the feldspathic composition (highland) of the primary ejecta in rays emplaced on a mare substrate. Immature local substrate is only observed in Copernicus's ray at large unmantied secondary craters or other areas with sufficient topographic slope to prevent the accumulation of mature soils.

The Flamsteed region of Oceanus Procellarum is representative of an unsampled volcanic complex on the lunar nearside. The evolution of this region, as portrayed in the current surface, is investigated in detail. A synthesis of remote sensing data, including multispectral images (digital vidicon images and color composite photographs), spectral reflectance measurements, radar topographic maps, and orbital and earth‐based photography, is presented. Additional information is derived from crater degradation studies, radar backscatter, gravity measurements and orbital γ ray data. Seven spectrally distinct basaltic units, which range in age from 2.5±0.5 b.y. to 3.65±0.15 b.y., have been identified. Three have been formally named and related to the Procellarum lithostratigraphic nomenclature scheme. The earliest units within the mapped area are composed of highlands material and include partially flooded impact craters. Another early nonmare unit is spectrally distinct material that occurs as plains and domes and which, in part, is of probable extrusive origin. Small amounts of dark mantle material suggest the presence of an early Ti‐rich basalt (Repsold Formation) beneath the presently exposed mare basalts. The oldest surface exposed mare basalts are very low Ti basalts of the Telemann Formation. These are overlain by low to intermediate Ti basalts of the Hermann Formation. The youngest exposed basalts are the moderately Ti‐rich members of the Sharp Formation. The unsampled Flamsteed basalt, a young Ti‐rich unit defined here, is comparable to Apollo 11 basalts in many measurable parameters except the strength of an absorption feature at 1 μm. This distinction implies a fundamental difference in mineralogy of the two titanium‐rich units; the Flamsteed basalts may be more iron rich than the other lunar basalts. The total mare fill in the Flamsteed region is probably of the order of 400‐m average thickness. Ejecta from young craters such as Kepler and Copernicus overlie some basalts. The major deformation of these units, evidenced by tectonic rules and mare ridges, terminated prior to the emplacement of the youngest mare unit during the emplacement of the Hermann Formation. This complexity of emplacement history and wide variety of observed basalt types, largely unsampled by Apollo and Luna missions, provide additional details of basaltic volcanism on the moon and require models of lunar basalt petrogenesis to be reexamined.

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