New evidence could help restore Pluto's planethood. Images from NASA’s New Horizons mission reveal the “dwarf planet” may have clouds, which would indicate a weather system.

In order to be considered a planet, outer-space bodies have to meet a set of criteria. It must circle the sun without being some other object’s satellite; be rounded by its own gravity; not be so big to undergo nuclear fusion like a star; and clear its neighborhood of most orbiting bodies. Pluto failed on this last count, as it shares most of its space with other objects from the Kuiper Belt. So, in 2006 the International Astronomical Union (IAU) striped it of its planet status back in 2006. However, not everyone agrees with the IAU's standards for what defines a planet. 

Alan Stern, head of the New Horizons mission, believes this criteria to define a planet is flawed. He believes it passes what he refers to as the “Star Trek test”--you know a planet when you see it.

“When you’re watching a science fiction show like “Star Trek” and they show up at some object in space and turn on the viewfinder, the audience and the people in the show know immediately whether it’s a planet, or a star, or a comet or an asteroid,” Stern told Space.

These images may help rekindle the debate among astronomers and restore Pluto to its rightful place as the ninth planet in our solar system.

Will Grundy of Lowell Observatory told New Scientist, researchers have noticed “low-altitude features” and “bright cloud-like things” hovering above Pluto's icy surface. The team of researchers plans on releasing a paper in Science titled, “The Atmosphere of Pluto as Observed by New Horizons.” According to New Scientist, the discussion of Pluto's clouds will only be a passing mention.

There are still gigabytes of data waiting to be received by Earth scientists from the New Horizons probe. It takes time to transmit these findings from so far away. But the complexity of Pluto's atmosphere may have scientists over at IAU reconsidering their criteria for what makes a planet.


Photo Credit: NASA/JHUAPL/SwRI

Natalie has been writing professionally for about 6 years. After graduating from Ithaca College with a degree in Feature Writing, she snagged a job at where she had the opportunity to review all the latest consumer gadgets. Since then she has become a writer for hire, freelancing for various websites. In her spare time, you may find her riding her motorcycle, reading YA novels, hiking, or playing video games. Follow her on Twitter: @nat_schumaker