Weather forecast for the ‘dark side’ of Venus: Space-based infrared imaging reveals how winds run BACKWARDS at night on ‘Earth’s evil twin’

  • Researchers used infrared images from the Japanese Akatsuki Venus probe
  • They then stacked the images and filtered out the noise to see wind patterns
  • They found the night-time winds flow counter to the winds in the daytime
  • This could be fuelling the planet-wide super-rotation of the weather system
  • It is hoped new, accurate climate models can be created for Venus in future 

Winds run backwards at night on ‘Earth’s Evil Twin’ sister planet Venus, according to weather forecasts made using space-based infrared imaging.

This is the first time weather patterns have been ‘clearly observed’ on Venus at night, as Earth-based observations of the hellish planet’s night side are difficult. 

Earth and Venus have much in common as they reside in the same orbital region, known as the habitable zone, capable of supporting liquid water and possibly life.

Not only are they similar in size and mass, but both have a solid surface and narrow atmosphere with distinct weather patterns, at one point Venus had liquid water. 

With no direct sunlight, observing the weather patterns at night on a planet can be very difficult, but the Japanese team took infrared observations from an orbiter then worked to suppress the noise and stack different images to get a clear picture.  

Using the Venus Climate Orbiter Akatsuki probe, scientists at the University of Tokyo found night winds run in the opposition direction to day winds on Venus. 

Researchers think the dayside poleward circulation and newly discovered nightside equatorial circulation may fuel the planetwide super-rotation, the ferocious east-west circulation of the entire weather system around the equator.

They hope this observation will allow astronomers to create more accurate models of Venusian wether, that could also help understand Earth weather patterns as well. 

The three main weather patterns on Venus. Researchers think the dayside poleward circulation and newly discovered nightside equatorial circulation may fuel the planetwide super-rotation that dominates the surface of Venus

With no direct sunlight, observing the weather patterns at night on a planet can be very difficult, but the Japanese team took infrared observations from an orbiter then worked to suppress the noise and stack different images to get a clear picture 

VENUS: THE BASICS 

Venus, the second planet from the sun, is a rocky planet about the same size and mass of the Earth.

However, its atmosphere is radically different to ours – being 96 per cent carbon dioxide and having a surface temperature of 867°F (464°C) and pressure 92 times that of on the Earth.

The inhospitable planet is swaddled in clouds of sulphuric acid that make the surface impossible to glimpse via the visible light spectrum.

In the past, Venus likely had oceans similar to Earth’s – but these would have vaporised as it underwent a runaway greenhouse effect.

The surface of Venus is a dry desertscape, which is periodically changed by volcanic activity.

The planet has no moons and orbits the Sun every 224.7 Earth days. 

Scientists know very little about the weather at night on Venus, or any planet in the solar system.

This is due to the absence of sunlight, making imaging difficult.  

Now, researchers have devised a way to use infrared sensors on board the Venus orbiter Akatsuki to reveal the first details of the nighttime weather of Venus.

 Their analytical methods could be used to study other planets including Mars and gas giants as well. 

The methods could also allow researchers to understand more about the mechanisms underpinning Earth’s weather systems by studying other world’s and comparing it. 

To achieve this goal, researchers need to observe cloud motion on Venus day and night at wavelengths of infrared light.

However, until now only the weather on the daylight-facing side was easily accessible. 

Previously some limited infrared observations were possible of the nighttime weather, but these were too limited to paint a clear picture of the overall weather on Venus.

Enter the Japanese Venus Climate Orbiter Akatsuki and its infrared cameras.

Launched in 2010, it is the first Japanese probe to orbit another planet, with the goal of observing Venus and its weather system using a variety of instruments on board the spacecraft. 

Akatsuki carried an infrared imager which does not rely on illumination from the sun to see, but even this couldn’t directly resolve details on the nightside of Venus.

It did give researchers the data they needed to see things indirectly, which could then be expanded on to get a clear picture.

‘Small-scale cloud patterns in the direct images are faint and frequently indistinguishable from background noise,’ said Professor Takeshi Imamura from the Graduate School of Frontier Sciences at the University of Tokyo. 

‘To see details, we needed to suppress the noise,’ Professor Imamura explained. 

‘In astronomy and planetary science, it is common to combine images to do this, as real features within a stack of similar images quickly hide the noise. 

Data from the Venus orbiter Akatsuki is seen here showing the thermal signatures of clouds on the nightside of the planet for the first time

NEW MISSIONS TO VENUS

NASA and the European Space Agency recently announced three missions to Venus in the coming years.   

NASA announced its two new $500 million missions at the start of June, which will launch in the next 10 years to understand how Venus ‘became an inferno-like world’.

Just over a week later, the ESA said it will send a probe, known as EnVision, to study ‘Earth’s evil twin’, targeting a launch in the early 2030s. 

‘However, Venus is a special case as the entire weather system rotates very quickly, so we had to compensate for this movement, known as super-rotation, in order to highlight interesting formations for study.’

Graduate student Kiichi Fukuya, developed a technique to overcome this difficulty.

Super-rotation is one significant meteorological phenomenon that we do not get down here on Earth, explained Fukuya. 

It is the ferocious east-west circulation of the entire weather system around the equator, and it dwarfs any extreme winds we might experience at home. 

Imamura and his team explore mechanisms that sustain this super-rotation and believe that characteristics of Venusian weather at night might help explain it.

‘We are finally able to observe the north-south winds, known as meridional circulation, at night. What’s surprising is these run in the opposite direction to their daytime counterparts,’ said Imamura. 

‘Such a dramatic change cannot occur without significant consequences. 

They hope this observation will allow astronomers to create more accurate models of Venusian wether, that could also help understand Earth weather patterns as well

‘This observation could help us build more accurate models of the Venusian weather system which will hopefully resolve some long-standing, unanswered questions about Venusian weather and probably Earth weather too.’

US space agency NASA recently announced two new missions to explore Venus with probes named DaVinci+ and Veritas, and the European Space Agency also announced a new Venus mission named EnVision. 

Combined with the observational capacity of Akatsuki, Imamura and his team hope they will soon be able to explore the Venusian climate not just in its present form but also over its geological history, to a time when it was more ‘Earth-like’.

Their findings were published in the journal Nature.

CARBON DIOXIDE AND SULPHURIC ACID DROPLETS FEATURE IN THE ATMOSPHERE OF VENUS

Venus’s atmosphere consists mainly of carbon dioxide, with clouds of sulphuric acid droplets. 

The thick atmosphere traps the sun’s heat, resulting in surface temperatures higher than 470°C (880°F).

The atmosphere has many layers with different temperatures. 

At the level where the clouds are, about 30 miles (50 km) up from the surface, it’s about the same temperature as on the surface of the Earth.

As Venus moves forward in its solar orbit while slowly rotating backwards on its axis, the top level of clouds zips around the planet every four Earth days.

They are driven by hurricane-force winds travelling at about 224 miles (360 km) per hour. 

Atmospheric lightning bursts light up these quick-moving clouds. 

Speeds within the clouds decrease with cloud height, and at the surface are estimated to be just a few miles (km) per hour.

On the ground, it would look like a very hazy, overcast day on Earth and the atmosphere is so heavy it would feel like you were one mile (1.6km) deep underwater.

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