A new study suggests that a tiny, icy world beyond Pluto harbors a thin, delicate atmosphere. It's believed to be the smallest object yet with a clearly detected global atmosphere. Japanese astronomers reported Monday that this minor planet — a mini Pluto just 300 miles across — appears to have an atmosphere that's 5 million to 10 million times thinner than Earth's. They say it could have been created by volcanic eruptions or possibly a comet strike. The scientists used telescopes in Japan to observe the object two years ago in the solar system's Kuiper Belt.