Comets Are Not Wholly Pristine

In a recently paper published in Nature, Department of Space Studies researcher Alan Stern described a sharply changed view of comets that has evolved over the past 30 years. While we used to consider comets as wholly unchanged relics of the era of solar system formation that had been stored ever since in a distant, cold, timeless deep freeze reservoirs called the Oort cloud and the Kuiper Belt. Over time, however, researchers have demonstrated that a variety of processes serve to modify comets during their storage in these regions. As a result, it's become clear that the Oort cloud, and its cousin the Kuiper belt, are not such a perfect deep freeze. For more background, see: http://www.swri.org/9what/releases/oortrel.htm and the Nature paper.