REASON BEHIND VENUS' MYSTERIOUS ATMOSPHERIC BULGE

A mysteriously fluctuating bulge observed in the atmosphere of Venus now has a more concrete explanation. According to a newly published study, the planet's enormous mountain ranges are to blame for a massive gravity wave. Venus has a giant bow-like structure 10,000 kilometers wide that comes and goes from the upper atmosphere of the planet. It was first spotted by Japanese Venus orbiter Akatsuki in 2015, and spends days at a time staying perfectly still within Venus's otherwise turbulent atmosphere.

Venus is peculiar in many ways. It has a retrograde rotation - meaning it, like Uranus, rotates in the opposite direction to the rotation of the Sun, unlike most planets in our Solar System. It also rotates extraordinarily slowly; one day on Venus is around 243 Earth days. Venus's atmosphere, however, rotates around 60 times faster than the planet itself, making a full turn once every four days. This crazy motion results in winds of up to 400 kilometers per hour. 

"Over several days of observation, the bow-shaped structure remained relatively fixed in position above the highland on the slowly rotating surface, despite the background atmospheric super rotation," Japanese researchers wrote in the 2017 paper that described the wave for the first time. "We suggest that the bow-shaped structure is the result of an atmospheric gravity wave generated in the lower atmosphere by mountain topography that then propagated upwards."