Planetary-Scale Cloud Streaks Spotted On Venus

An infrared camera and supercomputer simulations have revealed planet-spanning cloud streaks over the surface of Venus.

AsianScientist (Jan. 18, 2019) – Observations from the spacecraft Akatsuki have helped to identify a giant streak structure among the clouds over Venus. These findings, from a group led by Assistant Professor Hiroki Kashimura of Kobe University, Japan, have been published in Nature Communications.

Often called Earth’s twin because of its similar size and gravity, Venus nonetheless has a very different climate. The sky of Venus is fully covered by thick clouds of sulfuric acid that are located at a height of 45-70 km, making it hard to observe the planet’s surface from Earth-based telescopes and orbiters circling Venus. Surface temperatures reach a scorching 460 degrees Celsius, a harsh environment for any observations by entry probes. Due to these conditions, there are still many unknowns regarding Venus’ atmospheric phenomena.

To solve the puzzle of Venus’ atmosphere, the Japanese spacecraft Akatsuki began its orbit of Venus in December 2015. One of the observational instruments of Akatsuki is an infrared camera named IR2. This camera can capture detailed cloud morphology of the lower cloud levels, about 50 km from the surface.

Before the Akatsuki mission began, the research team developed a program called AFES-Venus for calculating simulations of Venus’ atmosphere. Using the Earth Simulator, a supercomputer system provided by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), the research team created numerical simulations at a high spatial resolution. However, because of the low quality of observational data before Akatsuki, it was hard to prove whether these simulations were accurate reconstructions.

In the present study, researchers compared detailed observational data of the lower cloud levels of Venus taken by Akatsuki’s IR2 camera with the high-resolution simulations from the AFES-Venus program. The IR2 camera revealed nearly symmetrical giant streaks across the northern and southern hemispheres. Each streak is hundreds of kilometers wide and stretches diagonally almost 10,000 kilometers across. These streaks were successfully reconstructed with the AFES-Venus high-resolution simulations.

Through detailed analyses of the AFES-Venus simulation results, the team revealed that the giant streaks were caused by polar jet streams, a phenomenon closely connected to Earth’s everyday weather.

Until now, studies of Venus’ climate have mainly focused on average calculations from east to west. These new findings enable further discussions of the detailed three-dimensional structure of Venus, the researchers said.

The article can be found at: Kashimura et al. (2019) Planetary-scale Streak Structure Reproduced in High-resolution Simulations of the Venus Atmosphere With a Low-stability Layer.


Source: Kobe University; Photo: NASA.
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