Venus is covered with clouds of sulfuric acid that block our view of the surface. Clouds form at elevations of 30 to 45 miles (50 to 70 kilometers) when sulfur dioxide from volcanoes combines with water vapor to form sulfuric acid droplets. Any remaining sulfur dioxide should be quickly destroyed by intense solar radiation above 45 miles (70 km).
Thus, the detection of a sulfur dioxide layer 55-70 miles (90-110 km) by ESA’s Venus Express orbiter in 2008 posed a complete mystery. Where does this sulfur dioxide come from?
Now, computer simulations by Xi Zhang of the California Institute of Technology in Pasadena and colleagues from America, France and Taiwan show that some sulfuric acid droplets can evaporate at high altitudes, releasing sulfuric acid. gas which is then broken up by sunlight, releasing sulfur. dioxide gas.
“We hadn’t anticipated the high-altitude sulfur layer, but now we can explain our measurements,” ESA’s Hakan Svedhem said. “However, the new findings also mean that the atmospheric sulfur cycle is more complicated than we thought.”
As well as adding to our knowledge of Venus, this new understanding may warn us that the means proposed to mitigate climate change on Earth may not be as effective as originally thought.
Nobel laureate Paul Crutzen recently advocated artificially injecting large amounts of sulfur dioxide into Earth’s atmosphere about 12 miles (20 km) away to counter global warming resulting from increased greenhouse gases.
The proposal stems from observations of powerful volcanic eruptions, in particular the 1991 eruption of Mount Pinatubo in the Philippines which projected sulfur dioxide into the Earth’s atmosphere. Reaching 20 km above sea level, the gas formed small droplets of concentrated sulfuric acid, like those found in the clouds of Venus, which then spread around Earth. The droplets created a layer of haze that reflected some of the Sun’s rays back into space, cooling the entire planet by about 1 ° Fahrenheit (0.5 ° Celsius).
However, new work on the evaporation of sulfuric acid on Venus suggests that such attempts to cool our planet may not be as successful as initially thought. We don’t know how quickly the initially protective mist will be converted back to sulfuric acid gas – this is transparent and allows all of the sun’s rays to pass through.
“We need to study in detail the potential consequences of such an artificial layer of sulfur in the Earth’s atmosphere,” said Jean-Loup Bertaux from the University of Versailles-Saint-Quentin, France. “Venus has a huge layer of such droplets, so anything we learn about these clouds is likely to be relevant to any geoengineering of our own planet.”
Indeed, nature experiences it for us, and Venus Express allows us to learn the lessons before we experience our own world.