Rosetta has made the first detection of molecular nitrogen in the coma of Comet 67P/C-G.
The in situ detection of molecular nitrogen has long been sought at a comet. Nitrogen had only previously been detected bound up in other compounds, including hydrogen cyanide and ammonia, for example. Its detection is particularly important since molecular nitrogen is thought to have been the most common type of nitrogen available when the Solar System was forming. In the colder outer regions, it likely provided the main source of nitrogen that was incorporated into the gas planets. It also dominates the dense atmosphere of Saturn’s moon, Titan, and is present in the atmospheres and surface ices on Pluto and Neptune’s moon Triton.
It is in these cold outer reaches of our Solar System in which the family of comets that includes Rosetta’s comet is believed to have formed.