Image of the Day: Atmospheric gravity waves on Venus

Credit: ESA/Venus Express/VMC/A. Piccialli et al., 2014.

The atmosphere on Venus is insane. It's nasty, corrosive stuff, and at 70km thick, the temperature hits 450°C on the surface but drops to -70°C by the time you get to the top of the clouds. The expectation was that this meant that the atmosphere of Venus was stratified, like a layered cake, with very little mixing going on. But recent observations from the ESA's Venus Express orbiter shows what appear to be gravity waves in the atmosphere, created by Venusian mountains far below.

It's important to note that gravity waves are entirely different from gravitational waves. A gravitational wave is a wave in the fabric of space caused by sudden changes in gravity, like you might expect to find when two black holes collide with each other. We've actually got sensors designed to detect gravitational waves, although we haven't definitively spotted one yet. Gravity waves, on the other hand, are what you get when you have two fluids flowing past each other. If one fluid displaces another fluid a little bit, gravity will try to restore equilibrium between them, creating an oscillating wave. This is how you get waves on the ocean: air moving over the water and displacing it slightly, and gravity trying to bounce it back.

Anyway, back to Venus. While it's true that the cloudy atmosphere of the planet prevents us from seeing whether there actually are mountains down there in the visible spectrum, we've had an exceptionally detailed map of the entire planetary surface since the early 1990s thanks to a spacecraft called Magellan that came equipped with a massively powerful radar. There's all kinds of bizarre stuff going on down there, including some bizarre fractured volcanoes that look kinda like spiders:

With these existing radar maps, planetary scientists have been able to correlate the gravity waves with Venusian surface topography, specifically a continent-sized region of mountains called Ishtar Terra. What this all suggests is that there's actually some mixing of the Venusian atmosphere, implying that energy is moving around a lot more than we thought it was. The reason that all of this is worth caring about, by the way, is that Venus is an excellent example of global warming gone absolutely bananas, and by understanding how the atmosphere works on Venus, we might be able to generate better models that could suggest ways of not screwing up our own atmosphere any more badly than we already have.

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