A dual origin for Neptune's carbon monoxide?
Abstract
Heterodyne observations of Neptune have provided a measurement of the CO(2-1) line profile with a total bandpass of almost 8 GHz and a resolution of 4 MHz. The lineshape indicates that the CO mole fraction in Neptune's atmosphere is not uniform, but increases by a factor of ∼2 from the troposphere/lower stratosphere (0.5 ppm at p>20 mbar) to the upper stratosphere (1 ppm at p<20 mbar). This indicates the existence of both external and internal sources of CO. The equivalent flux associated with the external source is ∼1×108 cm-2 s-1. We propose that the stratospheric CO results from a large (2 km) cometary impact that occurred ∼200 years ago, although there remains problems with this hypothesis.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- January 2005
- DOI:
- 10.1051/0004-6361:200400127
- Bibcode:
- 2005A&A...430L..37L
- Keywords:
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- planets and satellites: Neptune;
- radio-lines: solar system