Even further west than Gassendi, Aristarchus (Figure 10.20) is an extraordinarily bright crater on the Oceanus Procellarum. The crater is so bright that the subtle banding on the crater walls is often badly overexposed. Aristarchus is only 40 kilometers in diameter but its environs are fascinating, too. Just west of this brilliant crater is the smooth-floored and relatively dull Herodotus. Meandering like a river, north and west of Herodotus is Schroter's Valley and the so-called "Cobra's head." The valley narrows from a maximum width of 10 kilometers down to 1 kilometer. The whole region is completely different from anywhere else on the lunar surface but you do have to wait until a few days before full Moon to see it emerge from the morning terminator.
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