Europe's Rosetta spacecraft captured this image of Comet 67P/Churyumov-Gerasimenko on March 22, 2015, from a distance of 48.3 miles (77.8 kilometers).

Comets go way back to Solar System's birth

Comets are pristine remnants left over from the solar system's formation 4.6 billion years ago, rather than younger fragments created by collisions between larger bodies, a new stu...