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Huge stripe structure found in Venus Cloudtops



A Japanese research team has discovered a gigantic stripe structure in the cloud cover of Venus. The discovery is based on observations of Venus by the Japanese spaceship Akatsuki. The findings were published on January 9 in the journal Nature Communications.

Venus is unlike any other planet in the solar system. The entire planet is covered in dense sulfuric acid clouds between 45 and 70 km altitude. This thick shroud has prevented scientists from studying the so-called "sister planet" of the earth in detail. But Japanese researchers are making progress.

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

5. It discovered the massive stripe structure in the middle and lower cloud images of the Venus night side, which was captured by the IR2 camera (Infrared 2) on the orbiter. The IR2 observation data were not of high quality, and unfortunately the camera does not work anymore, so it was not possible to further investigate the structure and find out the cause of the strip.

  Venus in the ultraviolet light of the Akatsuki spacecraft from JAXA. The thick atmosphere of the planet makes it hard to watch. Photo credits: JAXA / Akatsuki / ISAS / DART
Venus in the ultraviolet courtesy of the JAXA probe Akatsuki. The thick atmosphere of the planet makes it hard to observe. Photo credits: 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 calculate Venus simulations & # 39; The atmosphere. This is something that is usually done on Earth to predict weather, storms and climate change. They hoped that the simulations and observations of Akatsuki together would reveal the nature of the stripes at the planetary level.

(Left) The lower clouds of Venus were observed with the Akatsuki IR2 camera. The bright areas show where the cloud cover is thin. You can see the stripe structure at the planet scale inside the yellow dotted lines. (Right) The plan structure reconstructed by AFES-Venus simulations. The bright parts show a strong drain. (Partial Editing of an Image in the Nature Communications Publication CC BY 4.0?

When it comes to Venus, simulations are an even more important tool to understand what's happening in the atmosphere of this planet because it's so difficult Observing this difficulty in observing Venus also make it difficult to confirm simulations.

However, AFES-Venus had already achieved some success and the program had been successfully used to study the super-rotation winds and polar temperature structures in the atmosphere To reproduce Venus used another simulator provided by the Japanese Agency for Marine Earth Science and Technology (JAMSTEC) to create numerical simulations of Venus with higher resolution.

The team analyzed the simulations and discovered what in their view causes these gigantic stripes The interplay of two at mospheric phenomena is the first cause of this structure, which is closely related to the everyday weather of the earth: polar jet streams.

Polar jet streams are formed here on Earth in the middle and high levels of the atmosphere. The simulations in this study show that the same thing happens on Venus. Both are formed by the great wind dynamics in the atmosphere of both planets. But something else is at work on Venus.

The formation mechanism for the stripe structure on a planetary scale. The huge vortexes caused by Rossby waves (left) are tipped by the high-width jet streams and stretch (right). Within the elongated vertebrae, the convergence zone of the stripe structure forms, a downflow occurs and the lower clouds become thin. The Venus turns in a westerly direction, so that the jet streams also blow to the west.

At lower latitudes, an atmospheric wave, due to the distribution of large-scale currents and the planetary rotation effect (Rossby wave), produces large vortices across the equator latitudes of 60 degrees in both directions. Venus is different from Earth when it comes to rotation. It turns in the opposite direction as the Earth, and it turns slowly: for one revolution of the Earth, the planet needs 243 days.

When the vortices are added to the polar-ray currents on Venus, the vortices tilt and stretch. Convergence zone between north and south wind forms as a dash. The north-south wind pushed out by the convergence zone becomes a strong downflow, resulting in a planetary scale stripe construction.

Polar views of atmospheric strips in the Venus atmosphere that capture the Akatsuki probe's IR2 instrument. C is the south pole view and D is the north pole view. Picture: Kashimura et. al. 2019.

The study is a successful combination of observational data and simulations. The atmosphere of Venus is difficult to study, and most studies have focused on two dimensions, from east to west. However, this study is beginning to add a third dimension to our understanding of Venus.

The team behind the study is confident about their results, but points out that this is not a complete picture of the causes of the gigantic streaks. As they say in their article: "Although we have discussed a possible formation mechanism of the strip-like structure at the planetary level as discussed above, we should note that the details of the disturbances, instabilities, and equilibrium of the angular momentum in our simulation are still unclear and need to be explored ,

They also state that further studies are needed to understand all the details behind the phenomena. "We need to understand these mechanisms to assess the robustness or sensitivity of the mechanism of speculation presented here. However, we will keep these further investigations for our future studies.

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