Venus is covered by a thick layer of clouds that extends between 45 and 70 km above the surface. These rapidly-moving clouds are mainly composed of micron-sized droplets of sulphuric acid and other aerosols (fine solid or liquid droplets suspended in a gas), the origin of which is unknown.
Earlier missions have shown that the clouds resemble Earth's light fogs, but their thickness creates an impenetrable veil.
The Venus Monitoring Camera (VMC) on board Venus Express has been observing the top of the cloud layer in visible, near-infrared and ultraviolet wavelengths. Ultraviolet observations have shown a wealth of new details including a variety of markings created by variable concentrations of different aerosols located at the top of the cloud layer.
The image presented here (top of the article) is a global view of the southern hemisphere of Venus, obtained from a distance of 30 000 km. The south pole is at the bottom, while equator is at the top.
The appearance of the cloud veil changes dramatically from the equator to the pole. At low latitudes, the shapes are spotty and fragmented. This is indicative of vigorous, convective movement – like that of boiling water in a pot – powered by the radiation of the sun heating the clouds and the atmosphere itself. The bright lace visible on top of the darker cloud deck is made of freshly formed droplets of sulphuric acid.
At mid latitudes, the scene changes – convective patterns give way to more streaky clouds indicating that convection is weaker here, as the amount of sunlight absorbed by the atmosphere decreases.
At high latitudes, the cloud structure changes again. Here it appears as a dense, almost featureless haze forming a kind of polar cap or 'hood' on Venus. The dark, circular feature visible at the lower edge of the image is one of the dark streaks usually present in the polar region, indicating atmospheric parcels spiralling around and towards the pole.
Additional images provide close-up views of the structures described above and show details never seen before. This is possible thanks to the elongated orbit of Venus Express, which allows imaging of the same phenomena from decreasing distances.
Source: ESA
Related stories:
To curious aliens, Earth would stand out as living planet
With powerful instruments scouring the heavens, astronomers have found more than 240 planets in the past two decades, none likely to support Earth-like life.
Ground-based observatories join forces with Venus Express
Data from Venus Express, which has been revealing new and crucial details about our closest planetary neighbour, will now be augmented by synoptic data from a coordinated ground-based observation campaign.
Venus Express' infrared camera goes filming
An exciting new series of videos from ESA’s Venus Express has been capturing atmospheric details of day and night areas simultaneously, at different altitudes.
Tracking alien turbulences
New images and data from ESA's mission to Venus provide new insights into the turbulent and noxious atmosphere of Earth's sister planet. What causes violent winds and turbulences? Is the surface topography playing a role in the complex global dynamics of the atmosphere? Venus Express is on the case.
40 years ago, UW researcher changed our view of the world
Forty years ago this month, thanks to an inventive University of Wisconsin-Madison scientist, our view of the world was changed forever.
Saturn joins Venus in the vortex club
Cassini's spectacular image of
Saturn's polar vortex, published this month by NASA, may provide astronomers with a missing piece in the puzzle of how that planet's atmosphere works. For planetary scientists studying Venus, the image was strangely familiar.
Vesper Could Explore Earth's Fiery Twin
Earth has a twin sister, and she's gone bad. The planet Venus is almost the same size as Earth, so it has been called Earth's twin. It's only about 30 percent closer to the sun than Earth, and at the dawn of the space age, scientists thought its cloudy atmosphere might hide a steamy jungle planet teeming with life. However, when the first American and Russian space probes visited Venus in the 1960s, it became clear that something had gone terribly wrong with the planet's ability to support life.
Happy birthday, Venus Express!
One year after its launch on 9 November 2005 and a few months into its science phase, ESA's Venus Express keeps working well and continues to gather lots of data about the hot and noxious atmosphere of the planet. Newly released images show additional details of the thick cloud deck that surrounds Venus.
