An Analysis of Lunar Swirls By Night and Day: Detection, Distribution, and Discernment of Swirls and Their Physical Properties Utilizing LRO Lyman-α and LROC Ultraviolet Maps

We report an examination of the lunar surface surveying for the wispy, sinuous, and even looping geomorphic features called lunar swirls utilizing the Lyman Alpha Mapping Project (LAMP) and the Lunar Reconnaissance Orbiter Camera (LROC). We detail several detection classes in which the swirls are identified and confirmed with these two ultraviolet instruments through both independent and combined surveys; many of them not previously detected in other regions of the electromagnetic spectrum. We hypothesize this due at least in part to the unique nighttime normal directional hemispherical geometry of LAMP at 121.6 nm which enables rare illumination conditions in which to view these highly surficial deposits. We further examine swirls for their variability in far- and near-ultraviolet (FUV and NUV) reflectance as a population, relative to their local surrounding regolith, and global regolith. An examination of swirl relative size compared to albedo, spectral slopes, and coincident crustal magnetic field strengths collected by Lunar Prospector's Fluxgate Magnetometer show no spatially correlated systematics. However, we also show that at weak magnetic anomalies Ly-α albedo varies substantially and as magnetism increases, Ly-α albedo decreases and reduces in variability. By combining FUV and NUV observations we can more effectively distinguish lunar swirls as a population relative to impact crater deposits and in turn enable an initial assessment of lunar swirl optical and physical properties (roughness, porosity, shock) relative to impact deposits and their surrounding regolith.