August 17 to 19, 1989 Range 11.5 million km 7.1 million mi.

August 17 to 19, 1989 Range : 11.5 million km (7.1 million mi.) to 7.9 million km (4.9 million mi.) Four black and white images of Neptune's largest satellite, Triton, show it's rotation between the first (upper left) image and the last (lower right). Resolution improves from about 200 km (124 miles) to 150 km (93 miles) per line pair. Triton's south pole lies in the dark area near the bottom of the disk. Dark spots, roughly 1,000 km (620 miles) across, occur near the equator, and show Triton rotation between images. The rotation appears to be synchronous with Triton's 5.88-day orbital period (i.e., Triton rotates on its axis in the same time it revolves around Neptune.) The spots' constant rotation rate and their visibility near the edge of the disk suggest the spots are surface features. Whatever atmosphere is present on Triton appears transparent enough that Voyager 2's cameras can see through it.