I can't find a link to this paper on the forum, so apologies if it has already been discussed.
L.Y.Yeung,S.Li,I.E.Kohl,J.A.Haslun,N.E.Ostrom,H.Hu,T.P.Fischer,E. A. Schauble, E. D. Young, Extreme enrichment in atmospheric15N15N.Sci. Adv.3,eaao6741 (2017).
Quote from this 2017 article in Space Daily:
Quote“We didn’t believe it at first,” said Yeung, the lead author of the study and an assistant professor of Earth, environmental and planetary sciences at Rice. “We spent about a year just convincing ourselves that the measurements were accurate.”
The story revolves around nitrogen, a key element of life that makes up more than three-quarters of Earth’s atmosphere. Compared with other key elements of life like oxygen, hydrogen and carbon, nitrogen is very stable.
Two atoms of it form N2 molecules that are estimated to hang around in the atmosphere for about 10 million years before being broken apart and reformed. And the vast majority of nitrogen has an atomic mass of 14. Only about 0.4 percent are nitrogen–15, an isotope that contains one extra neutron. Because nitrogen–15 is already rare, N2 molecules that contain two nitrogen–15s - which chemists refer to as 15N15N - are the rarest of all N2 molecules.
The new study shows that 15N15N is 20 times more enriched in Earth’s atmosphere than can be accounted for by processes happening near Earth’s surface.