Jupiter: The Great Red Spot(s)
Jupiter's Great Red Spot

Mosaic of Jupiter's Great Red Spot, as seen by Voyager 1

Image courtesy NASA, JPL

If you were looking for one landmark to distinguish our solar system -- sort of a "turn left at the burned-out Chuck E. Cheese" on an astronomical scale -- you could do far worse than Jupiter's Great Red Spot (GRS) -- or rather, spots. In 2000, the Hubble Space Telescope witnessed a second spot, nicknamed "Red Jr.," arise from the collision of three smaller spots. In 2008, Hubble spotted a third [sources: Daniels; Phillips].

The fact is, these cyclonal beauty marks whirl about the faces of the other gas giants, too, and possibly on their close cousins, the cool, starlike bodies called brown dwarfs. They just tend to come and go. And that's what makes Jupiter's two-to-three-Earth-wide anticyclone so special: Depending on whom you ask, it's been spinning for at least 136 years, and possibly longer than 349. Why the age gap? We know today's GRS was described by American astronomer Carr Walter Pritchett in 1878, but some believe it's the same "permanent spot" observed by Italian astronomer Gian Domenico Cassini in 1665 [sources: Encyclopaedia Britannica; Clavin; Daniels].

As for scenic overlooks, we recommend keeping your distance, both to take it all in and to avoid its 250-mph (400-kph) peripheral winds [source: Encyclopaedia Britannica].