How to make a jet engine out of a dirty ball of comet ice

How to make a jet engine out of a dirty ball of comet ice

Fig. 14.20 . Unexpected cometary motions are attributed to non-gravitational forces caused by jets of matter ejected from a cometís spinning, icy nucleus. In this illustration, the ejected material pushes the comet in the opposite direction to its motion, causing the comet to arrive closest to the Sun at a time later than expected. If the comet had been rotating in the opposite direction, the jets would have pushed the comet along in its original direction, resulting in an early arrival time.

Copyright 2010, Professor Kenneth R. Lang, Tufts University