A comet has a lot to hide. To most people, it’s among the most glamorous objects in the solar system—brilliantly illuminated, racing through space with its glowing tail streaming far behind it. That, at least, is how comets look from great distances, and only when they’re close enough to the sun for the outward-flowing solar wind to light them up and produce those signature tails. But deeper in space, without the solar floodlights?