Venus's days may be getting slightly shorter thanks to a bizarre mismatch in the rotations of its rocky body and its thick, toxic atmosphere.
Venus is a lot like Earth, with a similar size and surface make-up. But, our Sun-hugging sister planet is clouded by an atmosphere so dense scientists behind a study published in Nature Geosciences think its actually speeding up the planet’s rotation by about two minutes every Venusian day.
Although one Venusian rotation takes as much as 243 Earth days, its atmosphere charges much faster around the slowly spinning rock. The atmosphere spins about once every four Earth days. According to the researcher’s computer models, this adds up to a speed of more than 100 yards per second.
The thick, racing winds pummel and pull at Venus’s mountains, producing a 6,200-mile-long wave that Japan’s Akatsuki orbiter has previously pictured emerging and vanishing. This enormous bow-shaped bulge slices through the planet from pole to pole.
The incredible wind behind the wave tugs on Venus, the researchers think, speeding up its spin. The Sun’s gravity, on the other hand, may act like a finger on a spinning globe, limiting the planet’s rotation speed.
“Overall, a net force is exerted on the mountain, and the whole solid body follows,” Thomas Navarro, study author and researcher at the University of California, told Space.com. This could help explain why scientists have struggled to pin down a precise measurement of a Venusian day. According to Science News, estimates have varied by up to seven minutes.
“This work is very interesting,” planetary scientist Tetsuya Fukuhara of Rikkyo University in Tokyo, one of the researchers who first uncovered the atmosphere wave, told Science News.
Understanding how the planet’s surface interacts with its thick shroud of gases, Fukuhara said, is “the most important issue in the Venus atmospheric science. Venus is the closest thing to Earth that we know of,” Navarro said. But, it is incredibly difficult to know what is going on beneath its toxic gassy swaddle. “We’d like to know what’s inside,” said Fukuhara.
The Akatsuki (“Dawn”) orbiter has been spinning around Venus on an elliptical orbit since 2015. Originally launched in 2010, it first missed its goal and flew around the sun for five years, before engineers managed to thrust it into orbit around Venus.