Venus is a hellish toxic world, with a surface under high pressure and temperatures hot enough to melt lead and zinc. Venus's thick clouds and strange weather has fascinated scientists for decades, and now a particular feature in one has been revealed to have a big effect on the other.
Unlike on Earth, most solar radiation is absorbed by the higher clouds of Venus. Within those clouds, there are strange dark patches made up of a mysterious substance, which scientists call an “unknown absorber” because it absorbs certain specific ultraviolet light from the Sun. The absorber is not evenly distributed and these variations create hotter regions in the atmosphere, which affects both local areas as well as the large-scale global circulation of clouds. In a study published in The Astronomical Journal, astronomers show that these patches of unknown absorber are affecting Venus's weather.
The team used several years of data collected between 2006 and 2017 by Venus Express, Akatsuki, MESSENGER, and the Hubble Space Telescope and discovered a change in the albedo, the ratio between the light reflected and light absorbed by a surface. The albedo of the clouds varied roughly by a factor of two around the planet over those 11 years. According to models, this might have produced changes in heat by up to 40 percent at the lower latitudes of Venus. They concluded these variations changed the movement of clouds around the planet.
“It is hard to conceive of what would cause a change in the albedo without a change in the absorbers,” co-author Sanjay Limaye, a planetary scientist at the University of Wisconsin-Madison, told Erica Naone at Astronomy.com.
The change in the absorbers perplexed astronomers. Not knowing what they're made of, the team has struggled to understand what processes are driving their changes. They proposed several mechanisms, from cosmic rays to regular changes in the solar activity, to different amounts of sulfur dioxide.
A more outlandish hypothesis has the absorbers actually being of biological origin. While the surface of Venus is hellish, the cloud-top is mild enough to possibly sustain life. This idea has been kicking about since the late 1960s and last year, Limaye and colleagues took a serious look at this possibility.
Limaye suggested to IFLScience at the time that simulating the condition seen in the clouds of Venus in greater detail from the comfort of the lab – in particular NASA’s Glenn Extreme Environments Rig – might deliver some much-needed answers regarding the true nature of the unknown absorbers of Venus, before we go there ourselves.
