Bright streaks radiating from young lunar craters. They have no surface relief and darken with age, probably due to mixing with the regolith and to exposure to radiation. They are most probably composed of fine rock powder and glass produced during the impact. The classic example is the spectacular rays emanating from the lunar crater Tycho (85 km diameter), conspicuous through binoculars at full Moon. Hundreds of rays radiate from the crater and some extend across the visible face of the Moon.
Subjects: Earth Sciences and Geography — Astronomy and Astrophysics.