<P> Because Triton's surface indicates a long history of melting, models of its interior posit that Triton is differentiated, like Earth, into a solid core, a mantle and a crust . Water, the most abundant volatile in the Solar System, comprises Triton's mantle, enveloping a core of rock and metal . There is enough rock in Triton's interior for radioactive decay to power convection in the mantle to this day . The heat may even be sufficient to maintain a global subsurface ocean similar to what is hypothesized to exist beneath the surface of Europa . The black material ejected is suspected to contain organic compounds, and if liquid water is present in Triton, it has been speculated that this could make it habitable for some form of life . </P> <P> Triton has a tenuous nitrogen atmosphere, with trace amounts of carbon monoxide and small amounts of methane near its surface . Like Pluto's atmosphere, the atmosphere of Triton is thought to have resulted from evaporation of nitrogen from its surface . Its surface temperature is at least 7001356000000000000 ♠ 35.6 K (7001355499999999999 ♠ − 237.6 ° C) because Triton's nitrogen ice is in the warmer, hexagonal crystalline state, and the phase transition between hexagonal and cubic nitrogen ice occurs at that temperature . An upper limit in the low 40s (K) can be set from vapor pressure equilibrium with nitrogen gas in Triton's atmosphere . This is colder than Pluto's average equilibrium temperature of 7001440000000000000 ♠ 44 K (7001441499999999999 ♠ − 229 ° C). Triton's surface atmospheric pressure is only about 1.4--7000190000000000000 ♠ 1.9 Pa (0.014--7000190000000000000 ♠ 0.019 mbar). </P> <P> Turbulence at Triton's surface creates a troposphere (a "weather region") rising to an altitude of 8 km . Streaks on Triton's surface left by geyser plumes suggest that the troposphere is driven by seasonal winds capable of moving material of over a micrometre in size . Unlike other atmospheres, Triton's lacks a stratosphere, and instead has a thermosphere from altitudes of 8 to 950 km, and an exosphere above that . The temperature of Triton's upper atmosphere, at 7001950000000000000 ♠ 95 ± 5 K, is higher than that at its surface, due to heat absorbed from solar radiation and Neptune's magnetosphere . A haze permeates most of Triton's troposphere, thought to be composed largely of hydrocarbons and nitriles created by the action of sunlight on methane . Triton's atmosphere also has clouds of condensed nitrogen that lie between 1 and 3 km from its surface . </P> <P> 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 . These observations indicate Triton is approaching an unusually warm summer season that happens only once every few hundred years . Theories for this warming include a change of frost patterns on Triton's surface and a change in ice albedo, which would allow more heat to be absorbed . Another theory argues the changes in temperature are a result of deposition of dark, red material from geological processes . Because Triton's Bond albedo is among the highest within the Solar System, it is sensitive to small variations in spectral albedo . </P>

Is triton the coldest place in the solar system