On Venus' cloud top chemistry, convective activity and topography: A perspective from HST
In: Icarus; (2020)
Online
Elektronische Ressource
Hubble Space Telescope Imaging Spectrograph (HST/STIS) observations were obtained on 3 dates in December 2010 and January 2011 recording the cloud top properties over Aphrodite Terra and a low elevation region downwind of Aphrodite through LSTs extending from 7 to 11 a.m. From these data we trace the cloud top sulfuroxide chemistry and UV albedo sensitivity to LST, latitude and topography. Above regions co-located in LST and latitude, albedo variations observed at 245 nm parallel those observed at 365 nm-following the pattern expected from Hadley cell circulation. However, darkening of the cloud top albedo at LSTs between 9.5 and 11 h beyond that expected from simple Hadley circulation was also observed. Above the plains the albedo darkening intensified rapidly with LST and was observed at latitudes extending as high as ~30 N; however, above the mountains the darkening was either entirely absent or evident only at 0 N at an intensity 2× lower than that observed over the plains. Because the observed 245 nm albedo LST variations were inconsistent with that expected from multiple scattering of the coincidently retrieved SO2 gas abundance, we conclude that the 245 nm albedo is diagnostic of the vertical and spatial distribution, abundance (and potentially the identity) of Venus' unidentified UV absorber—rather than SO2 gas. The LST albedo trends are best explained by the onset of subsolar convective activity that intensifies with LST expanding vertically from the boundary between the middle and upper clouds to the cloud tops and increasing the detectability of the unknown absorbing species at the cloud tops. The terrain dependence in the observed intensity implies the time at which the expansion reaches the cloud tops is later above the mountains than over the plains. Additionally, at the time of observation, the lowlatitude large-scale vertical mixing rates that control the latitudinal gradients of the SO2 and unknown absorber abundances above and within the cloud top
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On Venus' cloud top chemistry, convective activity and topography: A perspective from HST
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Quelle: | Icarus; (2020) |
Veröffentlichung: | 2020 |
Medientyp: | Elektronische Ressource |
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