Noble gas Noble gas The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a group of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemical reactivity. The six noble gases that occur naturally are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn). These elements are all nonmetals. Oganesson (Og) is variously predicted to be a noble gas as well or to break the trend due to relativistic effects; its chemistry has not yet been investigated. For the first six
Atmosphere of Titan comets. The difference suggests that cometary material is unlikely to be the major contributor to Titan's atmosphere. Atmosphere of Titan The atmosphere of Titan is the layer of gases surrounding Titan, the largest moon of Saturn. It is the only thick atmosphere of a natural satellite in the Solar System. The presence of a significant atmosphere was first suspected by Spanish astronomer Josep Comas i Solà, who observed distinct limb darkening on Titan in 1903, and confirmed by Gerard P. Kuiper in 1944 using a spectroscopic technique that yielded an estimate of an atmospheric partial pressure of methane of the