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Giant Streak Structure Found in Venus Cloudtops



A research group in Japan has discovered a giant string structure in Venus cloud peaks. The discovery is based on observations by Venus of the Japanese spacecraft Akatsuki. The findings were published in January 9 in the journal Nature Communications.

Unlike any other planet in the solar system, Venus is. The whole planet is incorporated into thick molar sulfuric acid between heights of 45 km to 70 km. This thick dress has prevented researchers from studying the so-called "sister plane" of the earth in detail. But Japanese scientists are making progress.

The discovery of these giant strikes began with the Japanese spacecraft Akatsuki. Akatsuki, also known as Venus Climate Orbiter, is a mission of the Japan Aerospace Exploration Agency (JAXA). The spacecraft has been circulating around Venus since December 201

5. It discovered the massive streak structure in middle and lower cloud images of the Venus night side taken by IR2 (Infrared 2) camera on orbiter. Observation data from IR2 was not high quality, and unfortunately the camera no longer works, so it has not been able to investigate the structure anymore and to annoy the cause of the stretch.

  Ultraviolet Venus by JAXA's Akatsuki Spacecraft. The Earth's thick atmosphere makes it difficult to observe. Credit: JAXA / Akatsuki / ISAS / DART
Venus in ultraviolet courtesy of JAXA's Akatsuki spacecraft. The Earth's thick atmosphere makes it difficult to observe. Credit: JAXA / Akatsuki / ISAS / DARTS / Damia Bouic

The Japanese team, led by Project Assistant Professor Hiroki Kashimura, (Kobe University, Graduate School of Science), used a computer program called AFES-Venus to compute Venus simulations & # 39; atmosphere. This is usually done on earth to predict weather, storms and climate change. They hoped that the simulations and observations from Akatsuki together would reveal nature on the planet scale.

(Left) The lower cloud of the Venus was observed with the Akatsuki IR2 camera. The bright parts show where the cloud cover is thin. You can see the plane's scale-shaped structure within the yellow dotted lines. (Right) The structural scale in the planetary shape is reconstructed through AFES-Venus simulations. The bright parts show a strong downflow. (Partial editing of the image in Nature Communications paper. CC BY 4.0?

In the case of Venus, simulations are an even more important tool for understanding what is happening in that planet's atmosphere, because it is so difficult to observe it. Venus also makes it difficult to confirm simulations.

But AFES-Venus had already been successful, the program has been successfully used to reproduce the super rotational winds and polar temperature structures in Venus & # 39; s atmosphere, also used another simulator provided by Japan. Agency for Marine Earth Science and Technology (JAMSTEC) to create higher resolution numerical simulations of Venus.

The team analyzed the simulations and discovered what they think causes these gigantic strokes, formed by the interplay of two atmospheric phenomena. is a phenomenon that is closely linked to the Earth's daily weather: polar jets

Polar beam currents form in the middle and high levels of the atmosphere here on earth. The simulations in this study show that the same thing happens on Venus. Both are shaped from large-scale wind dynamics in the atmosphere of both planets. But at Venus there is something else at work.

The formation mechanism of the planetary scale strip structure. The giant vortexes caused by Rossby waves (left) are tilted by the high latitude beam currents and extend (right). Within the stretched vortexes, the convergence zone is formed in the bar structure, a downflow occurs and the lower clouds become thin. Venus rotates in western direction, so the jet currents also blow west.

At lower latitudes, due to the distribution of large-scale flows and the planetary rotational effect (Rossby wave), an atmospheric wave generates large vortexes across the equator to latitudes of 60 degrees in both directions. Venus is different from Earth when it comes to rotation. It rotates in the opposite direction than the Earth and rotates slowly: It takes the planet 243 Earth days to complete a rotation.

When the vortexes are added to the polar beam currents on Venus, the vortexes twist and extend and convergence zone between the north and south wind is formed as a dash. The north-south wind that is pushed out of the convergence zone becomes a strong downward flow, which results in a planetary structure.

Polar views of the atmospheric lines in the Venus atmosphere captured by the IR2 instrument on the Akatsuki spacecraft. C is the south polar view and D is the northern polar view. Image: Kashimura et. al. 2019.

The study is a successful combination of observation certificates and simulations. Venus atmosphere is difficult to study, and most studies have focused on two dimensions, from east to west. But this study begins to add a third dimension to our understanding of Venus.

The team behind the study is convinced of their findings, but they warn that it is not a complete picture of the causes of the gigantic strokes. As they say in their paper, "Although we have discussed a possible shaping mechanism for the planet's scale structure as above, we should note that the details of the disturbances, instability and angular momentum balance in our simulation are still unclear and continue to be investigated."

They also say that further studies are necessary to understand all the details behind the phenomena. "We need to understand these mechanisms to evaluate the robustness or sensitivity of the speculated formation mechanism presented here. However, we hold these further studies for our future studies."

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