The Edge of Darkness

art002e010208 (April 6, 2026) - As the Artemis II crew flew over the terminator, the astronauts described this boundary between day and night as "anything but a straight line." Crater rims along the terminator stand out as "islands" in the night. Giant chains of craters emanating from the 3.7-billion-year-old Orientale basin can be seen scouring the surface, stretching almost to the terminator. This tells a geologic story: these crater chains produced by the Orientale impact event mar the surface of the relatively flat Hertzsprung Basin (center of this image), which means that Hertzsprung Basin must be even older than Orientale!