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Mapping Titan’s haze and cloud with NIRSpec/JWST and comparison with VIMS.

Presentation #401.04 in the session JWST Views of the Outer Planets and their Moons (Oral Presentation)

Published onOct 23, 2023
Mapping Titan’s haze and cloud with NIRSpec/JWST and comparison with VIMS.

The haze layer that completely covers Titan has a dominant role in its climate. It determines the radiative balance in the atmosphere and is also a good tracer of the atmospheric circulation. The spatial and temporal characterization of the haze is therefore essential to understand the climate of Titan. This is also an important step for access to surface and cloud properties. Aside from that, clouds are also good tracers of Titan meteorology and are also a primary scope of our analysis.

Recently, the JWST (James Webb Space Telescope) has produced very high quality observations. The high spectral resolution (R~2700) NIRSpec spectro-images make it possible to find information about the haze and mist layers from the low stratosphere down to the troposphere. We are able to retrieve 3 dimensional maps of the haze and mist extinction and of their spectral behaviour. With the same analysis, we can also build a map of the surface albedo at several wavelengths. At last, we also characterize the properties of the cloud observed in the northern hemisphere around 50°N. But, for now, and due to RT solver limitations, we restricted the study to the parts of the cloud observed to incidence/emission angles lower that ~ 40°.

In this presentation with discuss the results and make comparison with the GCM predictions for this season in order to correlate the structurs in the haze layer with the circulation pattern. We also compare our results with the seasonal evolution as observed by VIMS/Cassini, and especially with the haze layer at the opposite season, in 2007.

During the JWST lifetime, we expect that we could complete the seasonal sounding of atmospheric properties over the period from the northern autumnal equinox to the winter solstice. This is a period which has been little observed but which corresponds to a complete turnover of the atmosphere circulation. Important changes should be observed during that period.

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