A new study suggests that a tiny, icy world beyond Pluto harbours a thin, delicate atmosphere that may have been created by volcanic eruptions or a comet strike.

Just 300 miles (500 kilometres) or so across, this mini Pluto is thought to be the solar system's smallest object, yet with a clearly detected global atmosphere bound by gravity, said lead researcher Ko Arimatsu of the National Astronomical Observatory of Japan.

"This is an amazing development, but it sorely needs independent verification. The implications are profound if verified," said Southwest Research Institute's Alan Stern, the lead scientist behind NASA's New Horizons mission to Pluto and beyond. He was not involved in the study.