NASA chief keeps saying 'Pluto is a planet' because it's a complex, amazing world

The long-standing debate over Pluto's planethood recently got a public boost from NASA Administrator Jim Bridenstine, who said the world should definitely be a planet.

Observations from NASA's New Horizons spacecraft in 2015 revealed that Pluto was far more complex than expected, with a probable underground ocean, organic materials (the potential precursors of life) on the surface and a multilayer atmosphere, Bridenstine said at the International Astronautical Congress in Washington late last month.

"I'm here to tell you, as the NASA administrator, I believe Pluto is a planet," Bridenstine said to applause from the audience as the conference opened to public attendance.

NASA Administrator Jim Bridenstine gives an update on the agency?s Artemis program and the critical role international partnerships have in returning astronauts to the Moon and going on to Mars at the 70th International Astronautical Congress, Friday, Oct. 25, 2019, in Washington. Photo Credit: (NASA/Bill Ingalls)

The agency head made similar comments about Pluto in late August. But despite the object's complex characteristics, by the official definition of the International Astronomical Union, which oversees all planetary naming conventions, Pluto is not a planet. 

In 2006, a time when many other worlds of Pluto's size were being discovered around the solar system, the body was reclassified as a dwarf planet. The status change came out of a controversial 2006 vote by scientists, with which New Horizons principal investigator Alan Stern and others do not agree.

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