Astronomers have mapped the atmospheres of exoplanets for a while, but a good look at their night sides has proven elusive — until today. An MIT-led study has provided the first detailed look at a “hot Jupiter” exoplanet’s dark side by mapping WASP-121b’s altitude-based temperatures and water presence levels. As the distant planet (850 light-years away) is tidally locked to its host star, the differences from the bright side couldn’t be starker.
The planet’s dark side contributes to an extremely violent water cycle. Where the daytime side tears water apart with temperatures beyond 4,940F, the nighttime is cool enough (‘just’ 2,780F at most) to recombine them into water. The result flings water atoms around the planet at over 11,000MPH. That dark side is also cool enough to have clouds of iron and corundum (a mineral in rubies and sapphires), and you might see rain made of liquid…
