Gigantic atmospheric anomaly on Venus finally explained

At a glance:

• Astronomers have solved a decade-long mystery about massive atmospheric waves on Venus
• The phenomenon is caused by a "hydraulic jump" that forces sulfuric acid vapor higher into the atmosphere
• These waves, up to 3,728 miles wide, help maintain Venus's superrotation winds that move 60 times faster than the planet's rotation

The Decades-Long Mystery

In 2016, Japan's Akatsuki Venus orbiter began detecting colossal waves of acidic clouds sweeping through the planet's atmosphere. For nearly a decade, astronomers struggled to reconcile these observations with existing atmospheric models. These persistent cloud disruptions appeared repeatedly, forming massive structures that could stretch up to 3,728 miles (6,000 kilometers) across and linger for extended periods. The phenomenon had actually been observed since at least 1983, with ESA's Venus Express mission between 2006 and 2022 confirming similar patterns, yet the underlying cause remained elusive.

The challenge stemmed from Venus's extreme environment. Despite its similar size, mass, and density to Earth, Venus possesses a dense atmosphere and scorching temperatures that make it exceptionally difficult to study. The planet's thick cloud cover, while making it an "excellent" target for atmospheric research according to the study, also obscured detailed analysis of lower and middle atmospheric layers. "We identified the phenomena, but for years we couldn't understand it," Takeshi Imamura, the study's first author and a planetary scientist at the University of Tokyo, explained in a statement.

The Hydraulic Jump Solution

The breakthrough came when researchers identified a "hydraulic jump" as the mechanism behind these massive cloud formations. Hydraulic jumps are surprisingly common phenomena, observable even in a kitchen sink where running water forms a smooth inner circle of shallow, fast-flowing water surrounded by ripples of deeper, slower water. On Venus, a similar process occurs when an eastward atmospheric wave in the lower-to-middle cloud region becomes unstable, creating a "shock" that forces air to rise sharply along a front.

This sudden vertical movement carries sulfuric acid vapor higher into the atmosphere until it eventually condenses into clouds that encircle the entire planet. "Thanks to this research, we're now able to show that this cloud disruption is caused by the largest known hydraulic jump in the solar system," Imamura stated. The team's numerical simulations further suggested that this hydraulic jump process helps maintain Venus's superrotation—the phenomenon where massive winds circulate sulfuric acid clouds around the planet at speeds approximately 60 times faster than Venus's own rotation.

Venus's Atmospheric Layers

The Venusian atmosphere consists of three distinct layers of sulfuric acid clouds, each playing a different role in the planet's atmospheric dynamics. The upper clouds have been more accessible to study through probes like Akatsuki, but the lower and middle layers presented significant challenges for researchers. These superrotation winds not only move clouds at incredible speeds but also regulate the planet's radiative energy budget and influence atmospheric chemistry and dynamics.

The difficulty in studying these lower atmospheric layers meant that previous models couldn't fully explain the observed cloud phenomena. Imamura discovered this limitation firsthand in 2016 when Akatsuki began transmitting images of the recurring, sweeping cloud waves. The persistence of these features, confirmed by multiple missions and spanning decades, indicated a fundamental atmospheric process that existing theories failed to capture.

Broader Implications for Space Exploration

Beyond solving a planetary mystery, these findings have significant implications for future space missions. The research suggests that similar hydraulic jump processes may occur on other celestial bodies, including Mars, the Sun, and even Earth's atmosphere. This understanding becomes increasingly crucial as humanity expands its presence in space, where accounting for atmospheric conditions is vital for protecting astronauts and spacecraft.

"Our next step will be to test this discovery within a more inclusive climate model that includes other atmospheric processes," Imamura noted. "Under some circumstances, Mars' atmosphere may also have the right conditions for a hydraulic jump." The research, while based on simulations, underscores how every detail matters when exploring unknown environments, potentially influencing mission planning and atmospheric modeling across the solar system.