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
Super-Earth suggest that the term Super-Earth might be limited to rocky planets without a significant atmosphere, or planets that have not just atmospheres but also solid surfaces or oceans with a sharp boundary between liquid and atmosphere, which the four giant planets in the Solar System do not have. Planets above 10 Earth masses are termed massive solid planets<ref name="mass/radius sold"></ref>/mega-Earths or gas giant planets depending on whether they are mostly rock and ice or mostly gas. The first super-Earths were discovered by Aleksander Wolszczan and Dale Frail around the pulsar PSR B1257+12 in 1992. The two outer planets (Poltergeist and