Scientists studying data from NASA’s New Horizons space mission have found evidence of ammonia on the surface of Pluto.

It’s an exciting find, says Cristina Dalle Ore, a planetary scientist at the Search for Extraterrestrial Intelligence (SETI) Institute and NASA Ames Research Centre, California, because by geological standards, ammonia can’t survive long on the surface of Pluto without being destroyed by ultraviolet light, cosmic rays, or other radiation.

“It’s really fragile,” she says. “When you have ammonia on the surface, that means that it got there recently.”

It’s also a strong indication that Pluto not only once had an underground ocean, but still does, because ammonia-containing water spewing from such an ocean is the compound’s most likely source.

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