Comet 103P/Hartley captured by the Epoxi mission.
NASA/JPL-Caltech/UMD
In the November issue, planetary scientist Matthew Knight described what comets are, where they come from, and how researchers know this information, in “The science of comets.” He talked about the nine spacecraft that have visited the dusty snowballs, including the Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) probe. This craft flew 435 miles (700 kilometers) from Comet 103P/Hartley November 4, 2010, and captured images and other data of the cometary nucleus. Below is a video that NASA compiled from the photographs that EPOXI took. For reference, Hartley 2’s peanut-shaped nucleus is just 1.4 miles (2.2km) long.
