We're so close to seeing Pluto up-close, but a single pebble could make NASA's mission go terribly wrong

If a spacecraft fatally collides with speeding debris billions of miles into space, would anyone hear the crash? No. But decades worth of science would be lost. Such is the fear of NASA's New Horizons team as the space probe nears its closest approach to Pluto and its five (possibly more) moons. As New Horizons speeds toward the icy planet — about 6,200 miles from the surface at about 31,000 miles per hour — it will be nearing the most perilous part of its journey yet. "The most dangerous ti...