The latest data downloaded from NASA's New Horizons spacecraft suggests that mountains of nitrogen ice thousands of feet high have evaporated into Pluto's atmosphere since the dwarf planet formed 4.5 billion years ago, and hundreds of tons of that gas escape into space each hour. New images of Pluto meanwhile show land forms that suggest heat is rising beneath the surface, with troughs of dark matter either collecting or bubbling up between flat segments of crust. Scientists discussed the findings Friday in their second major release of data collected when the $700 million New Horizons mission made a historic pass...