After Voyager's flyby of featureless Uranus, it was a surprise to see so many details on Neptune. These high-altitude clouds have widths of 50 - 150 km and are stretched over thousands of km parallel to Neptune's equator, they are mainly composed of methane ice. You can even see their shadows on the lower cloud layer of the planet. These methane clouds condense at pressures below one bar and move with enormous speeds of up to 1400 km/h in the opposite direction to that of the planet's rotation.