Venus is a planetary hotspot in the solar system due to its thick clouds that prevent heat from leaving. Because of these clouds, astronomers cannot see into the deep part of the planet’s atmosphere. However, a team of scientists managed to take a peek at the clouds’ middle layer using infrared wavelengths.
The new research of Venus’ clouds has been conducted by scientists at the Japan Aerospace Exploration Agency and collaborators. Their findings exposed the patterns and differences of clouds in the middle layer. They published the results in the Geophysical Research journal of the American Geophysical Union.
The Planetary Hotspot, Venus
According to NASA, Venus is the second innermost planet in the solar system and one of the four terrestrial planets in the system. While it is composed of a rocky surface with mountains higher than Earth’s, it features an impressive atmosphere filled with thick clouds, as if it is a Jovian planet. Astronomers have attempted several times to study the planet’s atmosphere, but the clouds have prevented them from seeing deep within.
So, scientists led by JAXA decided to use infrared imagery to know if they could see past the clouds. Fortunately, infrared images showed them multiple surprises regarding the events occurring in the middle layer of the clouds. Images revealed the differences in the dynamics and morphology between the top and middle layers of Venus’ clouds.
‘We observed completely unexpected events. We have discovered that the middle clouds are not as quiet or as boring as they seemed during previous missions,’ explained Javier Peralta, the lead author of the study and a scientist in the Institute of Space and Astronautical Science at JAXA.
The Insights in Venus’ Middle Layer Clouds
Venus expresses similar size and structure to Earth, but spins in the opposite direction, compared to other planets in the solar system. Its atmosphere is filled with dense clouds that cause the greenhouse effect to persist across all its regions. The greenhouse effect has a temperature capable of melting lead.
Earlier observations of Venus revealed volcanoes and deformed mountains below the clouds, which indicated its rocky surface. Thus, astronomers classified it as a terrestrial planet, in spite of the thick clouds.
JAXA and collaborators wanted to learn more about these beautiful yet mysterious clouds on the planet. They used the images obtained by the Akatsuki space probe that arrived at the planet’s orbit in December 2015. The spacecraft was launched to study Venus’ super-rotation, a unique phenomenon in its atmosphere.
Almost 1,000 infrared images have been examined by the scientists, which were collected by Akatsuki for more than a year. The camera could penetrate the topmost layer of Venus’ clouds that allowed observations of the middle layer. The reason how the camera could do was due to infrared wavelengths, wherein photon could go deep inside before they are reflected back.
The examination of the Venus’ middle layer clouds revealed the following interesting details:
- The clouds in the layer would change over a period of time.
- The clouds appear to be different from the ones found in the top layer, which has a height of 70 kilometers.
- Sometimes, darker bands of clouds get invaded by brighter bands, which can appear as mottled.
- The mottled appearance is suggested to be a result of the convection or vertical movement of heat and moisture in the planet’s atmosphere.
- Sometimes, the clouds look less stormy or featureless with multiple stripes.
Aside from those, the images unveiled changes in the hemispheres of Venus. The northern hemisphere darkened periodically from April to May 2016. The periodical darkening was found every four to five days. This part was not observed in previous studies and needed to be investigated further to determine possible causes.
The data pinpointed the rare clouds features on Venus as well. One of them was the hook-like dark filament that spanned about 7,300 kilometers in the northern hemisphere. It was observed between May and October 2016.
Lastly was the high contrast in the albedo property of the clouds. Akatsuki highlighted that the cloud layer could absorb light at infrared wavelengths. Scientists speculated that certain compounds or the thickness of the clouds might be possible causes of the albedo.
The Super-Rotation of Venus
As mentioned earlier, Akatsuki is in Venus’ orbit to gather information of the planet’s super-rotation. Data sent by the space probe has been used by the team to reconstruct Venus’ winds. They combined Akatsuki’s images with observational data from amateur observers and previous space missions.
Results showed that the super-rotating winds in the middle clouds were at times very rapid at Venus’ equator. There were times that the winds could have speeds of up to 50 kilometers per hour for several months.
Right now, scientists suspect that the clouds in the atmosphere and their albedo may be connected to the super-rotation. However, they need to conduct additional analyses of the data to learn more about their association. This is because other factors like the Sun’s heat, mountain waves, and frictional drag can also influence the phenomenon. Super-rotation is an atmospheric phenomenon wherein the atmosphere’s winds travel at velocities faster than that of the surface.