The mysterious dark side of Venus: Strange, chaotic clouds are revealed for the first time on the night face of Earth's 'evil twin'

  • Researchers looked at the wind and cloud patterns on the night side of Venus
  • They found a phenomenon called 'super-rotation' is irregular on the night side
  • Clouds on the night side are large, wavy, patchy, irregular, and filament-like
  • They are also dominated by unmoving phenomena known as stationary waves

It is often referred to as Earth's sister planet, but it seems that Venus may have more of a Jekyll and Hyde behaviour than our world.

Scientists have looked at the 'night side' of Venus for the first time, and discovered strange, chaotic clouds. 

The findings challenge scientists' current understanding of climate modelling, and shed new light on Venus, nicknamed 'Earth's evil twin'. 

Scroll down for video 

Scientists have looked at the 'night side' of Venus for the first time, and found that the atmosphere on this side acts extremely differently to the side of the planet facing the sun (artist's impression pictured) 

Scientists have looked at the 'night side' of Venus for the first time, and found that the atmosphere on this side acts extremely differently to the side of the planet facing the sun (artist's impression pictured) 

VENUS' NIGHT SIDE 

The researchers used a tool called the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on the Venus Express to see the clouds on the night side. 

Instead of capturing single images, VIRTIS gathered a 'cube' of hundreds of images taken simultaneously at different wavelengths – creating images of the night side with unprecedented quality.

Previous studies have suggested that super-rotation occurs in the same way on the night and day sides of Venus.

But the new research contradicts these findings, and instead suggests that super-rotation is more irregular on the night side.

The images showed that night side upper clouds form different shapes and morphologies than those found elsewhere.

The clouds are large, wavy, patchy, irregular, and filament-like patterns, and are dominated by unmoving phenomena known as stationary waves.

Advertisement

Researchers from the Japan Aerospace Exploration Agency (JAXA) have used the Venus Express spacecraft to look at the wind and cloud patterns on the night side of Venus.

They found that the night side has completely different cloud types, morphologies and dynamics to the dayside – some of which appear to be connected to features on the planet's surface.

Dr Javier Peralta, lead author of the study, said: 'This is the first time we've been able to characterise how the atmosphere circulates on the night side of Venus on a global scale.

'While the atmospheric circulation on the planet's dayside has been extensively explored, there was still much to discover about the night side.

'We found that the cloud patterns there are different to those on the dayside, and influenced by Venus' topography.'

Venus' atmosphere contains strong winds that whirl around the planet 60 times faster than Venus rotates.

This phenomenon, known as 'super-rotation', drags along clouds, with the fastest clouds travelling at a height of about 40 to 45 miles (65 to 72 kilometres) above the surface.

Dr Peralta said: 'We've spent decades studying these super-rotating winds by tracking how the upper clouds move on Venus' dayside - these are clearly visible in images acquired in ultraviolet light.

'However, our models of Venus remain unable to reproduce this super-rotation, which clearly indicates that we might be missing some pieces of this puzzle.

'We focused on the night side because it had been poorly explored; we can see the upper clouds on the planet's night side via their thermal emission, but it's been difficult to observe them properly because the contrast in our infrared images was too low to pick up enough detail.'

This sequence of images, taken with the VIRTIS instrument on Venus Express, shows stationary waves in the clouds above the night side of the planet 

These images show examples of new types of cloud morphology discovered on the night side of Venus. Top left shows stationary waves, top right shows 'net' patterns, bottom left shows mysterious filaments, and bottom right shows and dynamical instabilities

These images show examples of new types of cloud morphology discovered on the night side of Venus. Top left shows stationary waves, top right shows 'net' patterns, bottom left shows mysterious filaments, and bottom right shows and dynamical instabilities

STATIONARY WAVES  

The clouds on the dark side are dominated by unmoving phenomena known as stationary waves.

This finding raises questions about existing models of stationary waves, which suggested such waves were formed surface winds interacting with obstacles, such as mountains.

The researchers found that the planet's southern hemisphere is generally quite low in elevation, and – more mysteriously – stationary waves appear to be missing in Venus' intermediate and lower cloud levels.

Advertisement

The researchers used a tool called the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on the Venus Express to see the clouds on the night side.

Dr Peralta explained: 'VIRTIS enabled us to see these clouds properly for the first time, allowing us to explore what previous teams could not–and we discovered unexpected and surprising results.'

Instead of capturing single images, VIRTIS gathered a 'cube' of hundreds of images taken simultaneously at different wavelengths – creating images of the night side with unprecedented quality.

Previous studies have suggested that super-rotation occurs in the same way on the night and day sides of Venus.

Night side clouds form different shapes and morphologies than those found elsewhere–large, wavy, patchy, irregular, and filament-like patterns, and are dominated by unmoving phenomena known as stationary waves (shown in GIF)

But the new research contradicts these findings, and instead suggests that super-rotation is more irregular on the night side.

The images showed that night side upper clouds form different shapes and morphologies than those found elsewhere.

The clouds are large, wavy, patchy, irregular, and filament-like patterns, and are dominated by unmoving phenomena known as stationary waves.

Dr Peralta said: 'It was an exciting moment when we realised that some of the cloud features in the VIRTIS images didn't move along with the atmosphere.

'Our findings were confirmed when JAXA's Akatsuki spacecraft was inserted into orbit around Venus and immediately spotted the biggest stationary wave ever observed in the solar system on Venus' dayside.'

The researchers used the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on ESA's Venus Express spacecraft (artist's impression pictured) to see the clouds properly for the first time, allowing them to explore what previous teams could not

The researchers used the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on ESA's Venus Express spacecraft (artist's impression pictured) to see the clouds properly for the first time, allowing them to explore what previous teams could not

This finding raises questions about existing models of stationary waves, which suggested such waves were formed by surface winds interacting with obstacles, such as mountains.

But the researchers found that the planet's southern hemisphere is generally quite low in elevation, and – more mysteriously – stationary waves appear to be missing in Venus' intermediate and lower cloud levels.

Dr Ricardo Hueso, co-author of the study, said: 'We expected to find these waves in the lower levels because we see them in the upper levels, and we thought that they rose up through the cloud from the surface.

'It's an unexpected result for sure, and we'll all need to revisit our models of Venus to explore its meaning.'

The researchers hope the findings will help to create more accurate climate models in the future.

Hakan Svedhem, who also worked on the study, said: 'This study challenges our current understanding of climate modelling and, specifically, the super-rotation, which is a key phenomenon seen at Venus.'