Issue |
A&A
Volume 370, Number 2, May I 2001
|
|
---|---|---|
Page(s) | 610 - 622 | |
Section | Celestial mechanics and astrometry | |
DOI | https://doi.org/10.1051/0004-6361:20010259 | |
Published online | 15 May 2001 |
The deuterium abundance in Jupiter and Saturn from ISO-SWS observations
1
DESPA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon Cedex, France
2
Max-Planck-Institut für Extraterrestrische Physik, 85748 Garching, Germany
3
Space Research Organization of the Netherlands and Kapteyn Institute PO Box 800, 9700 AV Groningen, The Netherlands
Corresponding author: E. Lellouch, emmanuel.lellouch@obspm.fr
Received:
22
December
2000
Accepted:
14
February
2001
Observations with the Short Wavelength Spectrometer (SWS) onboard
the Infrared Space Observatory (ISO) are used to determine the D/H ratio
in Jupiter's and Saturn's atmospheres. The D/H ratio is measured
independently in hydrogen (i.e. from the HD/H2 ratio) and methane
(from CH3D/CH4). Observations of the HD R(2) and R(3)
rotational lines at 37.7 and 28.5 μm, of the H2
S(0) and S(1)
quadrupolar lines at 17.1 and 28.2 μm, of the methane
band at 7.7 μm, and of the CH3D
band at 8.6 μm are analyzed
jointly, allowing a retrieval of thermal profiles and molecular
abundances. On each planet, the D/H determinations from H2 and CH4
give consistent results, but the accuracy is not sufficient to
precisely determine
the enrichment factor of D/H in methane. Combining these
determinations, we obtain the following values for the D/H ratio in
hydrogen: (D/H)
in Jupiter
and
on Saturn. These
values are consistent
with and somewhat more accurate than most earlier values. Comparing
with inferences of protosolar D/H from solar wind measurements, it is confirmed
that Jupiter is a reliable indicator of the protosolar
D/H ratio. The protosolar deuterium abundance inferred from the jovian
value, (
, indicates a minor decrease of the D/H
ratio, over the last 4.55 Gyr, in the part of the Galaxy where the
Solar System was formed.
Although the error bars overlap,
most measurements, including ours, may point to
a slightly smaller D/H ratio in Saturn's atmosphere than
in Jupiter's, a surprising result which needs confirmation.
Key words: planets and satellites: Jupiter / infrared: solar system
© ESO, 2001
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