We present new results of our studies of zonal and meridional winds in both hemispheres of Venus, using ground- and space-based coordinated observations. The results obtained from telescope observations were retrieved with a Doppler velocimetry method. The wind velocities retrieved from space used an improved cloud-tracked technique based on the phase correlation between images. We present evidence that the altitude level sensed by our Doppler velocimetry method is approximately four kilometres higher (~4 km) than that using ground-tracked winds (using 380 or 365 nm). Since we often take advantage of coordinated space and ground observations simultaneously, this altitude difference will be very relevant in order to estimate the vertical wind shear at the related heights in future observation campaigns. We also explored a previous coordinated campaign using Akatsuki observations and its Ultraviolet Imager (UVI) at 283 and 365 nm filters, which showed that cloud-tracked winds showed a difference of about 10–15 ms−1, as in the case of the comparison between the Doppler velocimetry winds and the 365 nm cloudtracked winds. The results’ comparison also strongly suggested that the cloud-tracked winds based on the 283 nm filter’s images were sensing at about the same atmospheric altitude level as the Doppler winds. The observational results were compared with the ground-to-thermosphere 3D model developed at the Laboratoire de Meteorologie Dynamique (IPSL-Venus General Circulation Model (VGCM)) and AFES-Venus General Circulation Model (GCM), at several pressure levels (and related heights). The analysis and results showed the following: (1) additional confirmation of the coherence and complementarity in the results provided by these techniques on both the spatial and temporal time scales of the two methods; (2) we noticed in the following that the results from the two different Akatsuki/UVI filters (283 and 365 nm) showed an average difference of about 10–15 ± 5 ms−1, and we suggest this may be related to SO2 atmospheric fluctuations and the particular conditions in the coordinated observing time window; (3) we present evidence indicating that, in the context of our observations, visible Doppler methods (highly self-consistent) seem to sense wind speeds at a vertical level closer to or within the range sensed by the UVI 283 nm filter images (again, in the context of our observations); (4) modelling predicted wind profiles suggests that the layers of the atmosphere of Venus sensed by the methods referred to in Point 3 differ by approximately four km in altitude (~4 ± 2 km) regarding the cloud-tracked winds retrieved using 365 or 380 nm images.

At Venus’s cloud top, the circulation is dominated by the superroration, where zonal wind speed peaks at ∼100 ms−1, in the low-to-middle latitudes. The constraining of zonal and meridional circulations is essential to understanding the mechanisms driving the superrotation of Venus’s atmosphere, which are still poorly understood. We present new Doppler velocimetry measurements of horizontal wind velocities at Venus’s cloud top, around 70 km altitude. These results were based on March 2015 observations at the Canada–France–Hawaii Telescope (CFHT, Mauna Kea, Hawaii), using ESPaDOnS. The Doppler velocimetry method used has already successfully provided zonal and meridional results in previous works led by P. Machado and R. Gonçalves, proving to be a good reference ground-based technique in the study of the dynamics of Venus’s atmosphere. These observations were carried out between 27 and 29 March 2015, using the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) which provides simultaneous visible-near IR spectra from 370 to 1050 nm, with a spectral resolution of 81000 allowing wind field characterization in the scattered Franuhofer solar lines by Venus’s cloud top on the dayside. The zonal velocities are consistent with previous results while also showing evidence of spatial variability, along planetocentric latitude and longitude (local-time). The meridional wind circulation presents a notably constant latitudinal structure with null velocities at lower latitudes, below 10∘ N–S, and peak velocities of ∼30 ms−1, centered around 35∘ N–S. The uncertainty of the meridional wind results from ground observations is of the same order as the uncertainty of meridional wind retrieved by space-based observations using cloud-tracking, as also shown by previous work led by R. Gonçalves and published in 2020. These March 2015 measurements present a unique and valuable contribution to the study of horizontal wind at the cloud top, from a period when Doppler velocimetry was the only available method to do so, since no space mission was orbiting Venus between Venus Express ending in January 2015 and Akatsuki’s orbit insertion in December 2015. These results from new observations provide (1) constraints on zonal wind temporal and spatial variability (latitude and local time), (2) constraints on the meridional wind latitudinal profile, (3) additional evidence of zonal and meridional wind stability for the period between 2011 and 2015 (along previous Doppler results) (4) further evidence of the consistency and robustness of our Doppler velocimetry method.

The study of minor chemical species in terrestrial planets’ atmospheres can teach us about the chemistry, dynamics and evolution of the atmospheres through time. Phosphine or methane on terrestrial planets are potential biosignatures, such that their detection may signify the presence of life on a planet. Therefore, the search for these species in the solar system is an important step for the subsequent application of the same techniques to exoplanetary atmospheres. To study atmospheric depletion and the evolution of water abundance in the atmospheres of terrestrial planets, the estimation of the D/H ratio and its spatial and temporal variability is used. We used the Planetary Spectrum Generator (PSG), a radiative transfer suite, with the goal of simulating spectra from observations of Venus, Mars and Jupiter, searching for minor chemical species. The present study contributes to highlight that the PSG is an efficient tool for studying minor chemical species and compounds of astrobiological interest in planetary atmospheres, allowing to perform the detection and retrieval of the relevant molecular species. Regarding detection, it is effective in disentangling different molecular opacities affecting observations. In order to contribute to the scientific community that is focused on the study of minor chemical species in the solar system’s atmospheres, using this tool, in this work, we present the results from an analysis of observations of Venus, Mars and Jupiter, by comparison of observations with simulations in the infrared (IR). The first step was to clearly identify the position of molecular features using our model simulations, since the molecular absorption/emission features of different molecules tend to overlap. For this step, we used the method of the variation of abundances. The second step was to determine the molecular abundances and compare them with values from the literature using the retrieval method and the line depth ratio method. For Venus, our study of SO2-related observations by the Texas Echelon Cross Echelle Spectrograph (TEXES) at 7.4 μm enabled the identification of absorption lines due to sulphur dioxide and carbon dioxide as well as constrain the abundance of SO2 at the cloud top. Phosphine was not detected in the comparison between the simulation and TEXES IR observations around 10.5 μm. For Mars, both a positive and a non-detection of methane were studied using PSG simulations. The related spectra observations in the IR, at approximately 3.3 μm, correspond, respectively, to the Mars Express (MEx) and ExoMars space probes. Moreover, an estimate of the deuterium-to-hydrogen ratio (D/H ratio) was obtained by comparing the simulations with observations by the Echelon Cross Echelle Spectrograph (EXES) onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) at approximately 7.19–7.23 μm. For Jupiter, the detection of ammonia, phosphine, deuterated methane and methane was studied, by comparing the simulations with IR observations by the Infrared Space Observatory (ISO) at approximately 7–12 μm. Moreover, the retrieval of the profiles of ammonia and phosphine was performed.

<p>The study of the thermal spectrum of Jupiter gives us the possibility to study the elements that constitute the Jovian atmosphere, allowing us to infer the formation history and conditions of the giant planet (Taylor et al., 2004). Determining the abundance of chemical species and isotopic ratios is fundamental in this regard. For this, we reanalyse 1997 Jupiter data obtained by the ESA mission Infrared Space Observatory (ISO) (Kessler et al., 1996) in the 793.65-3125 cm-1 (3.2-12.6 µm) region using the Short-Wave Spectrometer (SWS) (de Graauw et al., 1996).  Despite the age of this data, we argue that it warrants a revisit and reanalysis since it was an important step in the study of Jupiter’s atmosphere and there have since been advancements in atmospheric models and line data.</p><p>In this work we used the NEMESIS radiative transfer suite (Irwin et al. 2008) to reproduce the observations from Encrenaz et al. (1999), which will also work as a validation of our method. Using the Cassini/CIRS model as a starting point, we adapted the template for the ISO/SWS data. We compiled correlated k-tables from the spectral line database from Fletcher et al. (2018) for a NH<sub>3</sub>, PH<sub>3</sub>, <sup>12</sup>CH<sub>3</sub>D, <sup>12</sup>CH<sub>4</sub>, <sup>13</sup>CH<sub>4</sub>, C<sub>2</sub>H<sub>2</sub>, C<sub>2</sub>H<sub>6</sub>, C<sub>2</sub>H<sub>4</sub>, C<sub>4</sub>H<sub>2</sub>, He and H<sub>2 </sub>atmosphere.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.ece30d39628269873172561/sdaolpUECMynit/2202CSPE&app=m&a=0&c=967973decff35ea7a1891e34420767cf&ct=x&pn=gnp.elif&d=1" alt="" width="792" height="462"></p><p><em>Figure 1: Plot of ISO/SWS and CIRS observations showing the discrepancy between both (no offset applied)</em></p><p>We first compare the spectrum obtained by ISO/SWS with the a priori model in order to find discrepancies between them as well as how each molecule individually impacts the forward model (Figure 1).</p><p>Our current work is focused on the 793.65-1500 cm<sup>-1</sup> (6.7-12.6 µm) region of the spectrum, for comparison reasons between the CIRS and ISO-SWS data, with the 793.65-1200 cm<sup>-1</sup> (8.3-12.6 µm) region showing the best fit.</p><p>We present here our preliminary results of the study of abundances of <sup>12</sup>CH<sub>3</sub>D, <sup>12</sup>CH<sub>4</sub>, <sup>13</sup>CH<sub>4</sub>, C<sub>2</sub>H<sub>2</sub> and C<sub>2</sub>H<sub>6</sub> of Jupiter’s atmosphere as well as our study of the pressure-temperature profile of Jupiter obtained using NEMESIS retrievals. We also compare our results with the profiles and abundances from Neimann et al. (1998) and Fletcher et al. (2016) with the aim of constraining the number of possible best fit profiles.</p><p>As consequence of the former study, we also present our initial study of the H/D and <sup>12</sup>C/<sup>13</sup>C isotopic ratio of the Jovian atmosphere from the abundances of <sup>12</sup>CH<sub>3</sub>D, <sup>13</sup>CH<sub>4</sub> and <sup>12</sup>CH<sub>4</sub> following the methodology from Fouchet et al. (2000).</p><p>We hope with this work to advance the understanding of the atmosphere of Jupiter and the physical and chemical processes that occur, as well as better determining its vertical distribution of chemical species and thermal profile. As future work, we expect to extend our frequency domain to the full range of ISO/SWS observations, study the <sup>15</sup>N/<sup>14</sup>N ratio and compare our finding with other relevant results.</p><p> </p><p> </p><p><strong>References:</strong></p><ul><li>de Graauw et al., Observing with the ISO short-wavelength spectrometer, A&A 315, L49-L54, 1996</li> <li>Encrenaz et al., The atmospheric composition and structure of Jupiter and Saturn form ISO observations: a preliminary review, Planetary and Space Science 47, 1225-1242, 1999</li> <li>Fletcher et al., Mid-infrared mapping of Jupiter’s temperatures, aerosol opacity and chemical distributions with IRTF/TEXES, Icarus 278, 128–161, 2016</li> <li>Fletcher et al., A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex, Nature Communications, Volume 9, 2018.</li> <li>Fouchet et al., ISO-SWS Observations of Jupiter: Measurement of the Ammonia Tropospheric Profile and of the 15N/14N Isotopic Ratio, Icarus 143, 223–243, 2000</li> <li>Irwin et al., The NEMESIS planetary atmosphere radiative transfer and retrieval tool, Journal of Quantitative Spectroscopy & Radiative Transfer 109, 1136–1150, 2008</li> <li>Kessler et al., The Infrared Space Observatory (ISO) mission, A&A 315, L27, 1996</li> <li>Neimann et al., The composition of the Jovian atmosphere as determined by the Galileo probe mass spectrometer, Journal of Geophysical Research Atmospheres 103(E10):22831-45, 1998</li> <li>Taylor et al., Jupiter, The Planet, Satellites and Magnetosphere, Ch.4, Cambridge Planetary Science, Eds. Bagenal, Dowling, McKinnon, 2004</li> </ul><p> </p><p><strong>Acknowledgements:</strong></p><p>We thank Thérèse Encrenaz, from LESIA, Observatoire de Paris, for providing the data for this work, Patrick Irwin, from the University of Oxford (UK), for the help with the NEMESIS radiative transfer suite and Maarten Roos-Serote for guidance and help in analysing the data and retrieval results.</p><p>We acknowledge support from the Portuguese Fundação Para a Ciência e a Tecnologia (ref. PTDC/FIS-AST/29942/2017) through national funds and by FEDER through COMPETE 2020 (ref. POCI-01-0145 FEDER-007672) and through a grant of reference 2021.04584.BD. </p>