The test launch of a Minuteman III missile from Vandenberg Air Force Base early Monday morning produced a beautiful and perfectly formed smoke ring, as shown in this picture spotted by Gizmodo. The Minuteman blastoff was part of a regimen of test launches held by the base to make sure all its systems are working properly. The ring was likely produced as smoke preceded the missile out of its silo — you can watch the whole process in this YouTube video (the smoke ring passes by at the 19 second mark):
Smoke rings aren't the only cool visual phenomenon that can accompany missile launches. One can also see holes in clouds, colorfully luminous vapor trails, and other rare sights depending on the lighting and atmospheric conditions.