CO2 is the main component of the atmosphere of Venus (96.5 %). The first measurements of the atmospheric composition of Venus were made by Adams and Dunham [Adams and Dunham, 1932] using the 100-inch reflector at Mount Wilson. They discovered three bands that they tentatively attributed to CO2. Since then, CO2 has been proven to be the main absorber in the infrared region. Its absorption bands are present throughout the spectral domain covered by SOIR, with intensities varying over a wide range of values.

Detection of a new band of absorption of 12C16O18O

The possibility to retrieve different isotopologues of CO2 has been illustrated by the discovery of the 01111-00001 band of 12C16O18O in the SOIR spectra.

First observation of 628 CO2 isotopologue band at 3.3 μm in the atmosphere
of Venus by solar occultation from Venus Express
Line parameters for the 01111–00001 band of 12C16O18O from SOIR measurements of the Venus atmosphere


Detection of CO2 isotopologues: 12C16O16O, 12C16O17O, 12C16O18O


(credit: BISA)

The isotopologues 12C16O16O, 12C16O18O, and 12C16O17O have been observed during MTP 21 which was fully dedicated to the measurement of CO2 and the determination of the
17O/16O and 18O/16O isotopic ratios as a function of altitude. Top panels show observed spectra recorded by SOIR and lower panels present the corresponding simulations. The ’*’ correspond to 12C16O17O lines absorbing in the same region as 12C16O18O and the ‘o’ to
12C16O18O line absorbing in the same region as 12C16O17O.

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Relevant Publications

Composition of the Venus mesosphere sosphere measured by SOIR on board Venus Express (pdf - 743 KB)
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