This is a list of the tallest mountains in the Solar System. The tallest peak or peaks on worlds where significant mountains have been measured are given; in some cases, the tallest peaks of different classes on a world are also listed. At 21.9km, the enormous shield volcano Olympus Mons on Mars is the tallest mountain on any planet in the Solar System. For 40 years, following its discovery in 1971, it was the tallest mountain known in the Solar System. However, in 2011, the central peak of the crater Rheasilvia on the asteroid and protoplanet Vesta was found to be of comparable height.[n 1]