Observations by Japan’s Venus climate orbiter Akatsuki have revealed an equatorial jet in the lower to middle cloud layer of the planet’s atmosphere, a finding that could be pivotal to unraveling a phenomenon called superrotation.
Observations by Japan’s Venus climate orbiter Akatsuki have revealed an equatorial jet in the lower to middle cloud layer of the planet’s atmosphere, a finding that could be pivotal to unraveling a phenomenon called superrotation.
Venus rotates westward with a very low angular speed; it takes 243 Earth days to rotate once. The planet’s atmosphere rotates in the same direction but at much higher angular speeds, which is called “superrotation.” The planet is covered by thick clouds that extend from an altitude of about 45 kilometers to 70 kilometers. The superrotation reaches its maximum near the top of this cloud, where the rotational speed is about 60 times that of the planet itself. The cause of this phenomenon, however, is shrouded in mystery.
Akatsuki was launched in 2010 by the Japan Aerospace Exploration Agency to unravel the atmospheric mysteries of Venus. Although lower-altitude clouds cannot be seen through with visible light, Akatsuki’s near-infrared camera IR2 successfully tracked the clouds – in particular, thicker clouds between 45 kilometers to 60 kilometers in altitude. This was made possible by observing the silhouettes of clouds that appear when infrared light from thermal radiation originating in the lower atmosphere filter through clouds.
Read more at Hokkaido University
Image: An illustration of Akatsuki successfully tracking lower-altitude clouds during the night with its near-infrared camera IR2. (Credit: PLANET-C Project Team)
