Japan’s Akatsuki spacecraft detects strong winds on Venus
Japan’s Akatsuki spacecraft orbiting Venus has spotted extremely strong winds near the planet’s equator blowing at speeds of over 178 mph (286 km/h). The newly discovered, high-velocity winds could provide important hints about the dynamics of the Venusian atmosphere.
The robotic Akatsuki probe is operated by the Japan Aerospace Exploration Agency (JAXA). The spacecraft was launched into space in May 2010 but failed to enter orbit around Venus during its first attempt in December 2010. Five years later, it was injected into an alternative elliptical Venusian orbit and started regular observations of the planet in March 2016.
Strong winds were imaged by Akatsuki’s IR2 infrared camera in mid-2016. Using a novel automated cloud tracking method, a group of researchers led by Takeshi Horinouchi of Hokkaido University in Japan was able to distinguish winds exhibiting a maximum rotational speed near the equator. They refer to this phenomenon as the equatorial jet.
“Here we report the detection of winds at low latitude exceeding 80 meters per second using IR2 camera images from the Akatsuki orbiter taken during July and August 2016,” the scientists wrote in a paper published on August 28 in Nature Geoscience. “The angular speed around the planetary rotation axis peaks near the equator, which we suggest is consistent with an equatorial jet, a feature that has not been observed previously in the Venusian atmosphere.”
The jet was spotted at an altitude between 28 and 37 miles (45 and 60 kilometers) above the planet’s surface. The research team used the infrared camera because these areas are invisible at optical wavelengths due to extremely dense clouds of sulfuric acid.
“Discovery of an equatorial jet is a giant step toward unraveling the mystery of super-rotation,” Horinouchi said.
Venus is well known for its super-rotating upper atmosphere as it rotates 60 times faster than its surface. The super-rotation reaches its maximum near the cloud top located at around 43 miles (70 kilometers) above the surface. There, rotational periods are three to five days, several tens of times faster than the planetary rotation.
“The mechanism producing the jet remains unclear,” the researchers said. “Our observations reveal variability in the zonal ﬂow in the lower and middle cloud region that may provide clues to the dynamics of Venus’s atmospheric super-rotation.”
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