astronomy, triton

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Triton, also known as Neptune I, is the biggest natural satellite of the outer planet, Neptune. It is the seventh-largest moon in the Solar System. It has a retrograde, inclined orbit around Neptune. Triton was discovered on October 10, 1846 by the astronomer William Lassell. It has a diameter of 2.7 megameters. All detailed knowledge of the surface of Triton was acquired from a distance of about 40,000 km by the Voyager 2 spacecraft. The surface of Triton has many blocky outcrops, ridges, troughs, furrows, hollows, plateaus, icy plains, as well with some craters located on the surface of this Neptunian moon, however, only the Southern hemisphere is known, so the Northern hemisphere might be different. Fifty-five percent of Triton's surface is covered with frozen nitrogen, with water ice comprising 15–35% and frozen CO2 forming the remaining. Triton's south polar region is covered by a highly reflective cap of frozen nitrogen and methane sprinkled by impact craters and openings of geysers. Little is known about the north pole because it was on the night side during the Voyager encounter, but it is thought that Triton must also have a north polar ice cap. In 1989, Voyager 2 data and images revealed an atmosphere around Triton. Triton has a tenuous nitrogen atmosphere, with trace amounts of carbon monoxide and small amounts of methane near its surface. Similar to Pluto's atmosphere, the atmosphere of Triton is thought to have resulted from the evaporation of nitrogen from its surface. In 1997, observations from Earth were made of Triton's limb as it passed in front of stars. These observations indicated the presence of a denser atmosphere than was deduced from Voyager 2 data. Other observations have shown an increase in temperature by 5% from 1989 to 1998.It is thought that the surface of Triton probably consists of a translucent layer of frozen nitrogen overlying a darker substrate, which creates a kind of "solid greenhouse effect". It is 800 kilometers high. The Voyager 2 probe in 1989 observed a handful of geyser-like eruptions of nitrogen gas and entrained dust from beneath the surface of Triton in plumes up to 8 km high. Triton is thus, along with Earth, Io, Europa and Enceladus, one of the few bodies in the Solar System on which active eruptions of some sort have been observed. The best-observed examples are named Hili and Mahilani (after a Zulu water sprite and a Tongan sea spirit, respectively). All the geysers observed were located between 50° and 57°S, the part of Triton's surface close to the subsolar point. This indicates that solar heating, although very weak at Triton's great distance from the Sun, plays a crucial role. Triton was most likely a Kuiper Belt object (KBO), but it got too close Neptune, and got captured. It might have been in a binary system with another KBO, but when Triton was captured, the other object got ejected into the outer reaches of the Kuiper Belt, or flung into interstellar space. Triton’s capture most likely caused many old moons to have their orbits become unstable and have them either ejected or pass the Roche limit of Neptune and got shredded into rings, due to a large and massive new object like Triton entering the system. After a few millions years, maybe even a billion or two, Triton’s orbit stabilized and new moons were born. In 3.6 billion years, Triton might pass the Roche limit of Neptune, and be shredded into a new pair of rings.