Rosetta SNIFFS molecular nitrogen on Comet 67P

Icy space rock came from way out there, but our atmosphere didn't

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The Rosetta orbiter has spotted molecular nitrogen, N2, on Comet 67P/Churyumov–Gerasimenko, the European Space Agency (ESA) has confirmed.

The ESA's relaying news from a freshly-published paper titled molecular nitrogen in comet 67P/Churyumov-Gerasimenko indicates a low formation temperature.

The presence of nitrogen on 67P matters because, to date, our exploration of comets has only found it present in other compounds. That's an oddity because we reckon there's plenty of standalone N2 in the atmospheres of the outer planets. It's therefore thought that when the solar system was congealing into its current form, there was lots of N2, in part because molecular nitrogen, as opposed to nitrogen in other compounds, only forms in very cold conditions. Like those found beyond Saturn.

Finding N2 on Comet 67/P therefore buttresses the theory that there's lots of the stuff out there, or was when the Solar System was forming.

But it's bad news for those who imagine comets may have brought nitrogen to Earth. Between Saturn and Earth there's not a lot of nitrogen to be seen, so comets bonking into Earth were thought to be a possible delivery mechanism.

The paper says that's probably not the case because the ratios of everyday nitrogen to the 14N and 15N nitrogen isotopes are different on 67P and Earth. If 67P is a typical comet, in terms of its N2 population, the theory that comets brought nitrogen to Earth becomes harder to sustain. ®


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