Variability of CO, OCS And H2O Below The Clouds of Venus From VIRTIS-HNight-side Spectra
Abstract
The VIRTIS imaging spectrometer has provided numerous spectra of Venus since the beginning of the Venus Express mission in April 2006. The high resolution of the H-channel (R 2000) enables the investigation of the composition below the clouds using the thermal emission from the night side of the planet, since several absorption of minor components (CO, OCS, H2O, HDO, SO2, HF) are located in the 2.3 µm transparency window of CO2. Using a radiative transfer computer model, we were able to derive constraints on the vertical profiles of CO, OCS and H2O in the 30-40 km altitude range up to areas unreacheable with Earth-based instruments (0° - 60°S). Our findings extend the latitudinal trends already noticed from both space (Collard et al., 1993, using Galileo/NIMS) and Earth (Marcq et al. 2005,2006, using IRTF/SpeX): an increase of CO towards high latitudes (30 ± 10 % between 60°S and 0°), a correlated decrease of OCS in the same region and a constant abundance of 28 ± 4 ppmv at 35 km for H2O. The latitudinal variations of CO are in good agreement with the VIRTIS-M observations from Tsang et al. (private communication). The quantitative interpretation of CO and OCS variations in terms of global-scale vertical circulation is in progress, using circulation models such as Yung et al's (private communication) in 2D and Lebonnois et al.'s (38th DPS meeting, #19.04) in 3D, thus helping in precising the understanding of both dynamics and chemistry in the deep atmopshere of Venus. This work has been funded by the CNES space agency.
- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #39
- Pub Date:
- October 2007
- Bibcode:
- 2007DPS....39.4505M