New Horizons' long journey to Pluto ended in an instant early this morning, when the NASA spacecraft went screaming past the dwarf planet at 30,800 mph -- but the mission is far from over. Even as the spacecraft speeds deeper into the Kuiper belt, its instruments will continue to search for signs of faint rings around the small world and take measurements of the dust and plasma in Pluto's neighborhood. And then there's all the new data that it has to get back to Earth. Little world, big heart: Pluto stuns in New Horizons image Little world, big heart: Pluto...