Science and Tech FeaturesFive Weirdest Weather Phenomena on Alien PlanetsScience and Tech Features - RSS 2.0
The falling sky of Pluto
No, we're not being alarmists - on Pluto, the sky is literally falling.
It is a popular misconception that Earth's seasons are caused by our planet being further away from the Sun during winter and closer during summer. Were this the case, then seasons would be a global phenomenon, rather than a hemispherical one caused by the Earth's axial tilt. But it is the case on Pluto.
The difference between the Earth's closest and furthest distance from the Sun is only about 5%. But Pluto's elongated orbit results in a huge discrepancy between its closest and furthest distances from the Sun - the dwarf-planet orbits at nearly twice the distance from the Sun during a "Plutonian winter" than it does during its summer.
As a result, scientists predict that as Pluto moves away from the Sun, its thin atmosphere of nitrogen, methane, and carbon monoxide gas gradually freezes and falls to the ground as ice. Then, as the dwarf-planet nears the Sun, Pluto warms until the ice sublimates back into a gas - that is, it transitions directly from solid to gas, skipping the liquid phase. Imagine a great mist rising and falling from the air - then consider that that mist is the atmosphere.