It Snows Sunscreen on This Planet

[Buster's Uncle]

It Snows Sunscreen on This Planet
Popular Mechanics
David Grossman  October 27, 2017



Photo credit: NASA, ESA, and G. Bacon (STScI)



Scientists at Penn State have discovered a planet outside of our solar system where it rains titanium oxide, the main ingredient in sunscreen.

Kepler-13Ab is one of the hottest known exoplanets, with dayside temperatures hitting close to 5,000 degrees Fahrenheit. Kepler-13Ab is tidally locked with its sun, meaning one side always faces the star while the other side is condemned to eternal darkness. The Penn State scientists were initially looking at the giant planet's atmosphere and how such temperature discrepancies would effect it when they discovered the raining sunscreen.

Using the Hubble's Wide Field Camera 3, the reserchers found that Kepler-13Ab's atmosphere is cooler at higher altitudes, unusual for "hot Jupiters" that orbit so close to their stars. There's titanium oxide in the atmosphere of most other hot Jupiters, but there the oxide absorbs light and reradiates it as heat, causing the gas giants to grow even warmer.

In this case, the scientists suspect there are mighty winds on Kepler-13Ab that push the titanium oxide to the planet's dark side, where it condenses into crystalline flakes that form clouds. With gravity six times greater than Jupiter's (which is already 2.4 times greater than Earth's), Keplar-13Ab than pulls the titanium oxide snow down from the clouds in the upper atmosphere and traps it in the lower atmosphere.

What it all means: Sunscreen snow is permanently falling and being trapped in the sky on half the planet, while the other half is 5,000 degrees. Thomas Beatty, assistant research professor of astronomy at Penn State and the lead author of the study revealing the findings, in a press statement:

Presumably, this precipitation process is happening on most of the observed hot Jupiters, but those gas giants all have lower surface gravities than Kepler-13Ab. The titanium oxide snow doesn't fall far enough in those atmospheres, and then it gets swept back to the hotter dayside, revaporizes, and returns to a gaseous state.

Studies of bizarre places like Kepler-13Ab not only highlight how mysterious the universe remains, but also offer clearer paths towards what we should expect when looking at Earth-like planets down the line.

"In many ways," Beatty says, "the atmospheric studies we're doing now on these gaseous 'hot Jupiter' kinds of planets are test beds for how we're going to do atmospheric studies of terrestrial, Earth-like planets."


http://www.popularmechanics.com/space/deep-space/news/a28813/scientist-discover-exoplanet-snowing-sunscreen/