5 research outputs found
Venus' atmosphere: an overview before next exploration missions
No full textInternational audienceDuring the last 15 years, our knowledge about the atmosphere of Venus has expanded greatly, mainly due to the contribution of two dedicated orbiters: Venus Express from ESA (2006-2014) and Akatsuki from JAXA (2015-present). Both missions included a comprehensive payload (imagers and/or spectrometers operating in the UV and/or IR range) which enabled them to measure key parameters about the atmosphere from the surface to the topmost layers. Among their discoveries are a much greater than anticipated spatial and temporal variability, in terms of minor species composition, cloud layers, dynamics and thermal structure. Most surprisingly, part of this variability was due to unsuspected coupling between the surface and the upper atmospheric layers at cloud top level. They also highlighted gaps in our knowledge, some of them long standing like the nature of the unknown UV absorber, that they could not solve. Undoubtedly, all these results contributed to the renewed interest for the planet Venus that was confirmed by the selection, in June 2021, of three space exploration missions targeting the planet in the 2030s. The science case of all these missions (DAVINCI and VERITAS from NASA, EnVision from ESA) include, to some extent, atmospheric characterization based on the aforementioned discoveries. This review talk will summarize our current knowledge about the atmosphere of Venus after Akatsuki and Venus Express, including some key outstanding questions. It will then proceed in a review of the planned atmospheric investigations from the above mentioned selected missions, as well as others from e.g. ISRO and Roscosmos
Venus' atmosphere: an overview before next exploration missions
No full textInternational audienceDuring the last 15 years, our knowledge about the atmosphere of Venus has expanded greatly, mainly due to the contribution of two dedicated orbiters: Venus Express from ESA (2006-2014) and Akatsuki from JAXA (2015-present). Both missions included a comprehensive payload (imagers and/or spectrometers operating in the UV and/or IR range) which enabled them to measure key parameters about the atmosphere from the surface to the topmost layers. Among their discoveries are a much greater than anticipated spatial and temporal variability, in terms of minor species composition, cloud layers, dynamics and thermal structure. Most surprisingly, part of this variability was due to unsuspected coupling between the surface and the upper atmospheric layers at cloud top level. They also highlighted gaps in our knowledge, some of them long standing like the nature of the unknown UV absorber, that they could not solve. Undoubtedly, all these results contributed to the renewed interest for the planet Venus that was confirmed by the selection, in June 2021, of three space exploration missions targeting the planet in the 2030s. The science case of all these missions (DAVINCI and VERITAS from NASA, EnVision from ESA) include, to some extent, atmospheric characterization based on the aforementioned discoveries. This review talk will summarize our current knowledge about the atmosphere of Venus after Akatsuki and Venus Express, including some key outstanding questions. It will then proceed in a review of the planned atmospheric investigations from the above mentioned selected missions, as well as others from e.g. ISRO and Roscosmos
A seasonally recurrent annular cyclone in Mars northern latitudes and observations of a companion vortex
No full textInternational audienceWe study a seasonally recurrent cyclone and related cloud phenomena observed on Mars at Ls ~ 120°, latitude ~ 60°N and longitude 90°W from images obtained with cameras in different spacecraft between 1995 and 2018. A remarkable double cyclone formed in 2012 and we present a detailed study of its dynamics using images from Mars Express and Mars Reconnaissance Orbiter obtained between June 6 and July 9. A double cyclone was also observed in 2006 and 2008. In other Martian Years the primary cyclone showed an annular cloud morphology with a large water ice cloud observed eastward of it. The cyclones have a size of ~ 600â800 km with a cloudâfree core of a radius ~ 100â300 km. Tangential velocities measured from cloud tracking in 2012 images are ~ 5â20 msâ1 at 10 km altitude and DC moved eastwards with a velocity of 4 msâ 1 during its lifetime of one month. The vortices grow in the morning hours, but with the increasing insolation as the sol progresses, a part of the clouds evaporate, the winds weaken and the vortices lose coherence. This phenomenon forms under high temperature gradients in a region with a large northâsouth topographic slope and has been recurrent each Martian year between 1995 and 2018. We argue the interest of studying its changing properties each Martian year in order to explore their possible relationship to the state of the Martian atmosphere at Ls ~ 120°
