Atmosphere of Triton asymmetry was actually observed during star occultations by Triton in 1990s. Before Voyager 2 arrived, a nitrogen and methane atmosphere with a density as much as 30% that of Earth had been suggested. This proved to be a great overestimate, similar to the predictions of the atmospheric density of Mars, but like on Mars, a denser early atmosphere is postulated. Voyager 2 flew past Triton five hours after closest approach to Neptune in mid-late August 1989. During the flyby, Voyager 2 took measurements of the atmosphere, finding methane and nitrogen in the atmosphere. In the 1990s, observations from Earth were
Atmosphere of Venus winds quickly decrease towards the higher latitudes, eventually reaching zero at the poles. Such strong cloud-top winds cause a phenomenon known as the super-rotation of the atmosphere. In other words, these high-speed winds circle the whole planet faster than the planet itself rotates. The super-rotation on Venus is differential, which means that the equatorial troposphere super-rotates more slowly than the troposphere at the midlatitudes. The winds also have a strong vertical gradient. They decline deep in the troposphere with the rate of 3 m/s per km. The winds near the surface of Venus are much slower than that on Earth.