Noble gas to be retained. Neon, argon, krypton, and xenon also form clathrate hydrates, where the noble gas is trapped in ice. Noble gases can form endohedral fullerene compounds, in which the noble gas atom is trapped inside a fullerene molecule. In 1993, it was discovered that when , a spherical molecule consisting of 60 carbon atoms, is exposed to noble gases at high pressure, complexes such as can be formed (the "@" notation indicates He is contained inside but not covalently bound to it). As of 2008, endohedral complexes with helium, neon, argon, krypton, and xenon have been obtained. These compounds
Atmosphere of Triton from NASA. Atmosphere of Triton The atmosphere of Triton is the layer of gases surrounding Triton. The surface pressure is only 14 microbars (0.014 hPa or 1 mmHg), of the surface pressure on Earth, and it is composed of nitrogen, similar to those of Titan and Earth. It extends 800 kilometers above its surface. Recent observations have shown an increase in temperature. Nitrogen is the main gas in Triton's atmosphere. The two other known components are methane and carbon monoxide, whose abundances are a few hundredths of a percent of that of the nitrogen. Carbon monoxide, which was discovered only