Cloud structure of Venus revealed by new observations using Akatsuki spacecraft and ground-based telescope

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K14786
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17010:Space and planetary sciences-related
• Research Institution: Hokkaido Information University
• Principal Investigator: Sato Takao 北海道情報大学, 経営情報学部, 准教授 (50633509)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 金星 / 雲層構造 / 探査機「あかつき」 / 地上望遠鏡 / 放射伝達 / 微量大気

Outline of Final Research Achievements

Optically thick clouds of sulfuric acid on Venus were observationally investigated by new observations using Akatsuki spacecraft and a ground-based telescope, IRTF. From near-infrared images of Akatsuki, the cloud tops were found to have an equatorially symmetric structure. The average cloud top altitude showed a gradual decrease from low to mid latitudes. It rapidly dropped from mid to high latitudes. The cloud tops on Venus are basically stable for nearly ten years in light of previous studies using past spacecraft data. The stationary gravity wave features first discovered in mid-infrared images of Akatsuki were also seen in the near-infrared images. The bright contrast of the features could be interpreted as resulting from the difference in cloud top altitude of a few hundred meters. The cloud tops derived from CO2 lines obtained by a high-resolution infrared spectroscopy using IRTF qualitatively supported the results from the near-infrared images of Akatsuki.

Free Research Field

宇宙惑星科学

Academic Significance and Societal Importance of the Research Achievements

全球を覆う光学的に厚い硫酸雲は金星全体の熱収支を支配しており，この振る舞いが金星の気候進化に大きく影響してきたと考えられる．従って，雲層構造の空間分布とその時間変動の理解は，金星の気候システムを解明する上で重要な基礎情報となる．本研究では，欧州探査機Venus Express以降では唯一となる雲層の詳細観測を実施した探査機「あかつき」と地上望遠鏡による観測データを用いて，雲頂高度分布と山岳波に起因した定在構造を含む微細構造について新たな知見を得た．これらは大気大循環モデルやデータ同化手法による大気現象の再現や気候システムの解明に必要な制約情報となった．