Xiao Zhao latitude: 10.56°N; longitude: 123.93°E
Scale: Xiao Zhao is 24 km (15 miles) in diameter
Hokusai latitude: 57.8°N; longitude: 16.8°E
Scale: Hokusai is about 85 km (53 miles) in diameter
Kuiper latitude: -11.35°N; longitude: 328.77°E
Scale: Kuiper is 62 km (39 miles) in diameter
Such rays are formed when an impact excavates material from beneath the surface and throws that material outward, thereby forming a crater and rays. The bright rays that result from the impact consist of both ejecta and secondary craters that form when the ejected material re-impacts the surface. Mercury and other airless planetary bodies are constantly being bombarded with micrometeoroids and energetic ions, producing an effect known as space weathering. Bright rays will slowly fade and darken over time, just like the surrounding materials, as a result of space weathering. Craters with bright rays are thought to be relatively young because the rays are still visible, indicating that they have had less exposure to such weathering processes than craters that lack rays. This high-resolution enhanced color view of Kuiper crater (far right) shows not just the bright rays that extend out from this relatively young crater, but also the redder color of Kuiper's ejecta blanket. The redder color may be due to a compositionally distinct material excavated from depth by the impact that formed Kuiper. In this sense, craters can provide a glimpse of what lies beneath the surface at the location of impact.