A SpaceX rocket is expected to collide with the moon on Wednesday at roughly 5,400 mph (8,700 kph) — about seven times the speed of sound — leaving a fresh crater near Einstein Crater on the moon's sunlit western edge. The impact is expected during the early hours of Wednesday, according to space tracking expert Bill Gray, who estimates the rocket's path. The discarded rocket stage weighs about 9,000 pounds. The collision itself will not be visible to the naked eye from Earth, but observers may see a plume of debris rising above the lunar surface, and photos from a lunar satellite are expected later. Best viewing conditions for a possible plume are likely across eastern parts of the United States and Canada, as well as much of South America.