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ESA Science & Technology: First detection of molecular nitrogen at a comet


Date: 19 March 2015

Rosetta has made the first detection of molecular nitrogen at a comet. The results provide clues about the temperature environment in which Comet 67P/Churyumov-Gerasimenko formed.

The graph shows the variation in the signals measured for molecular nitrogen (N2) and carbon monoxide (CO) by Rosetta's ROSINA instrument. The signals vary as a function of time, comet rotation and position of the spacecraft above the comet. An average ratio of N2/CO = (5.70 ± 0.66) × 10-3 was determined for the period 17–23 October 2014. The minimum and maximum values measured were 1.7 × 10-3 and 1.6 × 10-2, respectively (note that the ratio cannot be derived directly from this graph – a correction factor accounting for the instrument sensitivity is applied).

By comparing the ratio of N2 to CO at the comet with that of the protosolar nebula, it was determined that the comet must have formed at low temperatures, consistent with a Kuiper Belt origin. The study also finds that Jupiter-family comets like Comet 67P/Churyumov-Gerasimenko were unlikely the source of Earth's nitrogen.

Credits: Spacecraft: ESA/ATG medialab; comet: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0; Data: Rubin et al. (2015)


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Does the discovery of nitrogen signal anything special?

It confirms what we understood by analyzing Churi's water. Earth's water and atmospheric gas don't come from this kind of comet.

It was a big scientific objective of Rosetta: find if comets like Churi could be the ones who brought water on Earth, and possibly life (exo-genesis).

It seems to be confirmed now that the answer is no.

But it could be comets from another group, or even asteroids.

Mystery is still alive!

Fascinating! Is nitrogen a necessary ingredient for life? Or is it just hydrogen, oxygen, and carbon?

It's pretty neutral for humans, but it also is 78% of our atmosphere so it plays a role, and it came from somewhere.

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