Neptune

        Little was known about Neptune ,which was discovered in 1846, until the Voyager 2 encounter in 1989. It has a similar composition to Uranus and is close in mass to Uranus. Its thick atmosphere made of hydrogen, helium, and some methane and ammonia, gives it a bluish color. DISCOVERY         On August 25, 1989, the voyager discovered Neptune, but only after traveling 12 years at an average velocity of 19 kilometers a second (about 42 miles an hour). The Voyager 2 observed Neptune almost continuously …

…the face of the planet over distances of 1,000 km or more. If we return to the surface of Triton in a few decades it will probably not be like the images that the Voyager got in 1989. As the ices move around the moon the amount of sunlight falling on them will change and so will their temperature. The surface pressure on Triton could change by a factor of 10 or 100 during the course of a season.