ESA’s Venus Express spacecraft orbited at 66 000 km above the Venus south pole and captured bright and dark cloud bands wind around the poles of Venus, staring down into the south polar vortex. Venus Express has been orbiting the planet since 2006. It carries seven scientific instruments investigating the surface, atmosphere and ionosphere of Venus.
The movie bellow is based on images snapped by the Venus Monitoring Camera, observed through ultraviolet wavelengths, over a period of 18 hours during one of the spacecraft’s 24-hour elliptical, quasi-polar orbits around the planet on January 7-8, 2012. It was compiled using public data from the Venus Express data archive.
Intricate features on smaller and smaller scales are revealed as Venus Express dives to just 250 km above the north pole and clouds flood the field of view, before regaining a global perspective as it climbs away from the north pole. It reveals intriguing patterns in the cloud tops, which ride around the planet about 70 km above the surface. The observed pattern of bright and dark markings is caused by variations in an unknown absorbing chemical at the Venus cloud tops.
In 2007 the Venus Express probe discovered that a huge double atmospheric vortex exists at the south pole of the planet. Another discovery made by the Venus Express probe in 2011 is that an ozone layer exists high in the atmosphere of Venus.
Winds near the surface are only strong enough to move sand grains and dust particles, but the upper layers of the atmosphere move very fast. They circle the planet every four days, a pattern called super-rotation. Venus also has atmospheric circulation patterns between the equatorial and polar areas, similar to those on Earth.
The Earth takes one day to rotate on its axis, and it takes one year to revolve around the Sun in orbit. But Venus takes 243 days to turn once on its axis, and it takes almost 225 days to travel once around the Sun in orbit. As you can see, a day on Venus is longer than its year. If you were standing on the surface of Venus you would see the Sun rise in the west and then take 117 days to travel across the sky and then set in the east.
All the planets of the Solar System orbit in a counter-clockwise direction as viewed from above the Sun’s north pole, but Venus rotates clockwise. This is called ”retrograde” rotation. Astronomers think that Venus was impacted by another large planet early in its history, billions of years ago. The combined momentum between the two objects averaged out to the current rotational speed and direction. There are suggestions that Venus may have formed from the solar nebula with a different rotation period and obliquity, reaching to its current state because of chaotic spin changes caused by planetary perturbations and tidal effects on its dense atmosphere, a change that would have occurred over the course of billions of years.
Featured image: Artistic illustration of Venus Express and Venus (Credit: ESA)
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