Orbital Explorers: Venus Express and Akatsuki Missions Quiz

This structure remained stationary relative to the surface features below despite the high-speed winds. It is believed to be a gravity wave generated by lower-atmosphere winds flowing over high-altitude mountains like Aphrodite Terra.

The VIRTIS instrument detected localized areas of significantly higher temperatures that appeared and then cooled. These thermal signatures provide some of the strongest observational evidence that Venus is geologically active today.

These instruments allowed the mission to map surface temperatures, study the interaction between the solar wind and the ionosphere, and analyze the vertical chemical structure of the atmosphere.

Observations revealed a highly dynamic and complex vortex structure. The center of the vortex frequently splits into two or more centers of rotation, changing shape within hours due to the intense atmospheric super-rotation.

Akatsuki is specifically designed as a meteorological mission. By using cameras sensitive to different wavelengths, it tracks cloud movements to create 3D models of the wind speeds and energy transport that sustain the 4-day super-rotation cycle.

This surprisingly cold region (around 125 km altitude) is cold enough for carbon dioxide to freeze into ice or snow. This discovery challenged previous models that assumed the greenhouse effect kept all layers of the atmosphere relatively warm.

While visible flashes are hard to distinguish from cosmic rays, radio sensors have detected electromagnetic pulses consistent with lightning strikes. These likely occur within the sulfuric acid cloud layers rather than reaching the ground.

By comparing radar maps from the 1990s to newer data, scientists found that surface features were out of alignment. This suggests the thick, fast-moving atmosphere exerts enough friction on the surface to slightly alter the planet's rotation period over time.

A glory is caused by the diffraction of sunlight within cloud droplets. By analyzing this, Venus Express determined that droplets in the upper clouds are roughly 1.2 micrometers wide and composed of sulfuric acid.

Using infrared cameras, Akatsuki tracked the thermal silhouette of clouds on the dark side. It discovered that the night-side winds are more chaotic and influenced by different wave patterns than the solar-driven winds on the day side.

By watching stars pass behind the edge of the Venusian atmosphere, this instrument could see which wavelengths of light were absorbed, revealing how ozone, water vapor, and sulfur dioxide vary at different altitudes.

Observations in the lower cloud levels revealed a jet stream where winds move significantly faster than the surrounding atmosphere. This is vital for understanding how energy is transferred from the surface to the upper atmosphere.

Because Venus lacks a self-generated magnetic field, the solar wind slams directly into the upper atmosphere. This creates a magnetic barrier as the solar magnetic field lines get draped around the planet, protecting the atmosphere from even faster erosion.

There is a mysterious substance in the clouds that absorbs nearly half of the solar energy received by the planet. Akatsuki's UV imaging shows that these absorbers are distributed in complex, swirling patterns, playing a massive role in heating the atmosphere.

By looking at the infrared emissivity of the highland regions, Venus Express found signatures consistent with granitic rocks. Since granite on Earth forms in the presence of water, this suggests Venus may have had oceans in its geological past.

The intense heating of the sun creates a pressure wave that travels around the planet. Akatsuki has been instrumental in measuring how this thermal tide interacts with the background super-rotation to drive the global wind patterns.

While Akatsuki is in orbit, its cameras have specific filters. The Webb telescope can provide much broader and more sensitive spectral data from Earth's position, allowing scientists to cross-reference the chemistry with the real-time wind patterns seen by the orbiter.

Venus Express confirmed that the solar wind creates a bow shock where it meets the ionosphere. It also observed the stripping of ions from the atmosphere and how particles are accelerated away from the planet in a long magnetic "tail" trailing behind the planet.

By analyzing the ion escape rates, Venus Express confirmed that water is being stripped from the atmosphere by the solar wind. The observed 2:1 ratio of hydrogen to oxygen escape strongly suggests that the planet's original water content is being dissociated and lost to space.

Akatsuki suffered a propulsion system failure during its initial attempt. It spent five years orbiting the Sun before engineers successfully used its attitude control thrusters to perform a second, successful orbital insertion in 2015.