Gravity Waves May Cause Pluto's Hazy Atmosphere


Scientists may finally have an explanation for Pluto's streak-filled, hazy atmosphere. After analyzing data from the New Horizons probe that flew past Pluto in July 2015, scientists now think the dwarf planet's unique atmospheric characteristics are caused by gravity waves.

"Atmospheric gravity waves form when buoyancy pushes air up, and gravity pulls it back down," NASA explains. A good example of gravity waves is when air blows across the ocean and then runs into an island. It will be forced up and gravity will pull it back down on the other side. The result is a ripple pattern:

An example of a gravity wave on Earth.  NASA

"Any disturbance in the atmosphere can generate gravity waves, such as wind blowing over mountains, [and] evolving weather systems," Darrell Strobel, an atmospheric scientist and a New Horizons team member, told

(Gravity waves are not to be confused with gravitational waves — the space phenomenon that physicists detected for the first time ever in February.)

Gravity waves happen on Earth, Mars and several moons, and now, apparently, on Pluto. 

Pluto's multi-layer hazy atmosphere is full of light and dark streaks. You can see 20 different haze layers in the image below:

Source: NASA

Scientists now think those layers are created by gravity waves in the dwarf planet's atmosphere.

On Pluto, it's probably ice changing directly from a solid into a gas (sublimation) and gases freezing instantly into solids (deposition) that's causing the gravity waves and layers of haze to develop, Strobel said.

Scientists weren't expecting to find much of an atmosphere around Pluto at all. It's surprising how complex it's turning out to be.