Transcript: Neptune's Triton is the seventh largest moon in the solar system. With a diameter of 2,700 kilometers it's somewhat larger than Pluto. It has an unusual retrograde or backwards orbit of the planet which probably indicates that it was captured from interplanetary space somewhere during the history of the solar system. Triton has a sparse atmosphere made of nitrogen and methane, similar to the atmosphere on Saturn's Titan. The pressure is very low; it’s a thin atmosphere with barley 0.1 percent of the surface pressure of Mars’ atmosphere. Triton has volcanic vents where smoke plumes rise vertically 8 or 9 kilometers into the atmosphere and then are sheered off by high altitude winds. The surface is young and has probably been resurfaced. The cause of this is almost certainly tidal heating caused by changes in the orbit after its capture from interplanetary space.