Detection of HD in the atmospheres of Uranus and Neptune:
a new determination of the D/H ratio
H. Feuchtgruber, E. Lellouch, B. Bézard, Th. Encrenaz, Th. de
Graauw, and G.R. Davis
Abstract:
Observations with the Short Wavelength Spectrometer (SWS) onboard the
Infrared Space Observatory (ISO) have led to the first unambiguous
detection
of HD in the atmospheres of Uranus and Neptune, from its R(2)
rotational line at 37.7µm. Using S(0) and S(1) quadrupolar lines
of H2 at 28.2 and 17.0µm as atmospheric
thermometers,
we derive D/H ratios of 5.5x10-5
and 6.5x10-5 on Uranus and Neptune
respectively. This confirms that compared to Jupiter and Saturn, Uranus
and Neptune have been enriched in deuterium by the mixing of their
atmospheres with D-rich protoplanetary ices. Assuming complete mixing of
the planets, the D/H ratio in these
ices is however found to be lower than in cometary ices.
Keywords: Planets and satellites: general -- Planets
and satellites: individual: Neptune -- Planets and satellites:
individual: Uranus -- Solar system: formation -- Infrared: solar system
Status: A&A accepted
Address: mailto:
fgb@mpe.mpg.de
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