A whiff of methane

摘要

Methane is a constituent of many of the atmospheres in our Solar System: those of Earth, Mars, Titan and the gas giants Jupiter, Saturn, Uranus and Neptune all contain traces of it. Despite its low abundance, the methane provides telling clues about planetary formation, evolution, weather, photochemistry and - in the case of Earth - life. We have discovered more than 270 planets outside our Solar System, but for most of them we know nothing more than their mass and orbital properties. Owing to their immense distances from us, and their feeble brightness relative to the incandescence of the stars they orbit, obser-vationally inferring anything about their composition is extremely difficult.