The layering of rays across other surface features can be useful as an indicator of the relative age of the impact crater, because over time various processes obliterate the rays. On non-atmosphered bodies such as the Moon, space weathering from exposure to cosmic rays and micrometeorites causes a steady reduction of the differential between the ejecta's albedo and that of the underlying material. Micrometeorites in particular produce a glassy melt in the regolith that lowers the albedo. Rays can also become covered by lava flows (such as those of Lichtenberg on the moon), or by other impact craters or ejecta.
