Venus Is Boiling, Odd Dark Spots Suggest

Unless you live underground or in a very cloudy part of the world, it was pretty hard to miss the crazy conjunction of Venus and Jupiter Monday night that, when joined by the crescent moon, smiled on one side of Earth while frowning on the other.

But as millions of skywatchers reveled in that display, the folks over at ESA were preparing to release news about a slightly different view of lovely Venus.

Best known for being the brightest planet visible without the aid of a telescope, Venus gets even more interesting when you have the technology to peer under her skirts, so to speak, using wavelengths of light that are invisible to the human eye.


—Image courtesy ESA/MPS/DLR/IDA

In ultraviolet light, ESA’s Venus Express probe shows the planet as a smoky blue sphere with roiling bands of light and dark that highlight its complex structures of sulfuric acid clouds.

The big mystery, however, is which chemical in the Venusian clouds is absorbing UV light and thus creating the darker areas.

The planet’s dense cloud layer definitely covers the surface pretty thoroughly, as seen in optical images.

So why should some regions reflect UV while others absorb?


The shroud of clouds over Venus, as seen by the MESSENGER spacecraft in June 2007

—Image courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Meanwhile, in infrared the planet appears in fiery hues of orange, red, and near-black that show how high and how hot its cloud tops are—the darker the zone, the cooler the clouds.

Mixing the two sets of images allowed researchers, led by Dmitri Titov of the Max Planck Institute for Solar System Research in Germany, to link the mysterious dark zones seen in UV light to a process called natural convection.


—VMC ultraviolet image courtesy ESA/MPS/DLR/IDA; VIRTIS infrared image courtesy ESA/ VIRTIS/ INAF-IASF/ Obs. de Paris-LESIA

When water boils in a pot, the flame gets H2O molecules near the bottom hot and thus less dense, so they rise to the surface.

Colder molecules then sink to replace them, get heated up themselves, and rise back up. This process creates currents in the liquid, which we see as the familiar bubbling cauldron.

What Titov and co. found out is that in UV light, Venus sports a particularly dark region near its equator, signaling a concentration of the mysterious chemical.

In infrared, temperatures in this same region match a pattern of convection—clouds near the surface get heated up enough by the planet’s nightmare greenhouse effect that the atmosphere starts to “boil” and the clouds rise.

So. It seems Venus’s clouds are boiling, and this has something to do with the distribution of chemicals inside.

But the study still can’t answer the burning question of what exactly is this odd absorbent cloud component?

Back to you, science.

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