The dwarf planet Pluto and its system of five moons are about as mysterious as the underworld of antiquity that inspired their names. ... “We are still baffled by how the system formed,” says study co-author Mark Showalter, a senior research scientist at the Search for Extraterrestrial Intelligence (SETI) Institute. “I think everyone believes that, at some point in the distant past, a large object bashed into ‘proto-Pluto’ and the moons formed out of the debris cloud. However, after that point in the story, details get very sketchy.” Now, analysis of data collected from the Hubble Space Telescope following the...