Variability and Stability of the Venus' Atmosphere in Various Spatiotemporal Scales Inferred from Space Missions and Numerical Simulations----International Space Science Institute

Variability and Stability of the Venus' Atmosphere in Various Spatiotemporal Scales Inferred from Space Missions and Numerical Simulations

Context:

Venus, while being called often times as the earth’s twin sister, has distinctly different environment from ours: the atmosphere consists mostly of carbon dioxide with ~90 atmospheric pressures at the ground surface, hence the extreme greenhouse effect maintains high temperature of the surface, ~730 K. The globe is completely shrouded by the thick clouds (primarily sulfuric acid droplets) at about 50 – 70 km altitudes, making it difficult, if not impossible, to obtain 3-dimensional views of atmospheric dynamics (chemistry as well). In the 20th century, however, several entry probe missions from USSR and from USA enabled to partially study the sub-cloud atmospheric conditions. Still, our knowledge about the dynamics remained limited due to the lack of long-term continuous data with sufficient spatial coverage.
The situation has been improved in this 21st century by three major factors: the first one is the discovery of near-infrared transparency windows in the Venus’ atmosphere in 1983, which opened possibility to sense the sub-cloud atmosphere from the remote (partially utilized by NASA’s Galileo mission when it flew by Venus); the second one is ESA’s Venus Express mission which was in Venus orbit for over 8 years (2006 – 2014); and the third one is JAXA’s Akatsuki mission which was inserted to Venus orbit in December 2015 and is still actively acquiring the data (the mission extension approved until March 2029). Venus Express and Akatsuki together enhanced our knowledge about the atmospheric dynamics, not only limited to the cloud-top level but to some extent to sub-cloud regions. In addition, the observing duration from 2006 to 2024 (or even to 2029) provides an opportunity to study long-term variability from the data set of assured quality.

Objectives:
With such background, the aim of the workshop is to intensively discuss the variability and stability of the Venus’ atmosphere based on the analysis of data from space missions plus the numerical simulations. Since the duration of Akatsuki after the orbit insertion is becoming comparable to that of Venus Express, the data from both missions can be analyzed individually or by combination. We will identify what are alike or different in the periods of these two missions and interpret them in terms of mechanisms. Specific interests include the followings:

(a) Stability and variability of the zonal wind (super rotation) speed,

(b) Albedo (in ultraviolet) changes and the energy budget,

(d) Changes in atmospheric vertical structure (inferred from radio occultation).

As there are going to be more Venus missions (two from NASA, one from ESA, and from India, China, and Russia) in near future, summarizing our current knowledge about these should become an essential clue for the successors.

Product:
The book from this workshop will include at least 7 chapters: one overview of recent Venus missions, four for the above (a) – (d), one for numerical simulations, and one for provisions to future missions/studies. The target readers would range from undergraduates to early-career researchers who will actively work with today's data and sophisticated numerical models. The book is going to be the best summary of long-term data set (Venus Express and Akatsuki), the most comprehensive review of recent findings (both in the data analysis and the numerical simulations), and the convenient reference to plan for future missions (with support from the ground). Since Venus (a slow rotator) is considered as an analog for exoplanets (many of them are tidally-locked to the main star), this book will also be of great interests for the researchers of exoplanets.

Date: 02-06 June 2025

Takehiko Sato	Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan
Hiroki Ando	Kyoto Sangyo University, Japan
Takeshi Imamura	University of Tokyo, Japan
Jun Yang	Peking University, China
Yeon Joo Lee	Institute for Basic Science, South Korea
Silvia Tellmann	University of Cologne, Germany
Itziar Garate Lopez	University of the Basque Country, Spain
Kevin McGouldrick	University of Colorado Boulder, USA

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