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Molecular nitrogen in comet 67P/Churyumov-Gerasimenko indicates a low formation temperature
M Rubin1, K Altwegg2, H Balsiger3
1Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. martin.rubin@space.unibe.ch.
Science (New York, N.Y.)
|March 21, 2015
Summary
Molecular nitrogen (N2), crucial for planetary formation, was detected in comet 67P/Churyumov-Gerasimenko. This finding suggests cometary grains formed at extremely low temperatures, below 30 Kelvin.
Area of Science:
- Cosmic chemistry
- Planetary science
- Cometary science
Background:
- Molecular nitrogen (N2) is a significant nitrogen source in the early solar system.
- N2 is abundant in gas giants and icy bodies like Pluto and Triton.
- N2 has been notably absent in cometary samples, posing a puzzle for solar system formation models.
Purpose of the Study:
- To directly measure molecular nitrogen (N2) in a Jupiter family comet.
- To investigate the abundance and origin of N2 in comets.
- To understand the conditions of grain formation in the early solar system.
Main Methods:
- In situ measurement of molecular nitrogen (N2) using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) mass spectrometer.
- Analysis of N2 abundance relative to carbon monoxide (CO) in the comet's coma.
- Comparison of measured N2/CO ratios with protosolar values.
Main Results:
- Direct detection of molecular nitrogen (N2) in comet 67P/Churyumov-Gerasimenko.
- An N2/CO ratio of (5.70 ± 0.66) × 10(-3) was measured.
- This indicates a depletion of N2 by approximately 25.4 ± 8.9 times compared to the protosolar nebula.
Conclusions:
- Cometary N2 abundance is significantly lower than expected from protosolar composition.
- The observed depletion suggests cometary grains formed under very cold conditions (<30 Kelvin).
- This provides insights into the thermal history and chemical processes during solar system formation.
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