Is it the cloud cover or the enormous atmospheric pressure at the surface that makes Venus hot? Whatever, it seems the poles are colder than Earth, and by a wide margin, as Astronomy.com reports. Models based on a ‘greenhouse effect’ weren’t expecting this.
Thanks to a thick layer of cloud cover trapping in heat, Venus is the hottest planet in our solar system, with temperatures boiling over at 850 degrees Fahrenheit (454 C). But in a study published last week in Nature Physics, the European Space Agency found something surprising at the planet’s poles: temperatures more frigid than anywhere on Earth.
Even though ESA lost contact with the Venus Express probe two years ago after it ran out of fuel, the agency is still working through the data it returned. As the first spacecraft to explore our nearest neighbor since 1989’s Magellan mission, the probe revealed much about that world.
Many of the observations were made through plunging the craft into the atmosphere above the poles, where the probe encountered an atmosphere thinner than previously modeled, and filled with choppy atmospheric gravity waves, ripples caused by transfers of momentum between layers in the atmosphere.
“Concerning uniformity — models are mostly rather smooth while the reality is much more complex and structured,” ESA scientist and lead author Ingo Müller-Wodarg of Imperial College London said in an email to Astronomy. “We found enormous variability in the atmospheric densities that is explained by a combination of local (horizontal) day-night density variations but above all by strong periodicities, atmospheric waves. These are not captured by models.”
This marks the first time the poles of Venus have been directly studied, owing to Venus Express’ circumpolar orbit, which also allowed a global view. By crashing the probe through these winds on its final descent, the probe made the first ever in-situ observations of polar climates on Venus.
Phys.org reports: ‘Some of the final results sent back by ESA’s Venus Express before it plummeted down through the planet’s atmosphere have revealed it to be rippling with atmospheric waves – and, at an average temperature of -157°C, colder than anywhere on Earth.’