Evidence for a Collisional Mechanism Affecting Kuiper Belt Object Colors

The Kuiper belt region of the solar system, stretching from 30 to at least 50 AU, contains Pluto-Charon, some ∼105 Kuiper belt objects (KBOs) larger than 100 km in diameter, and myriad smaller bodies produced by collisions among KBOs (Farinella, Davis, & Stern, published in 2000). The most notable physical attribute of the KBOs discovered to date is their reflectance color diversity, ranging from gray (i.e., neutral) to very red (Tegler & Romanishin, published in 2000). I report here evidence for a statistical correlation between the colors of KBOs and the mean random impact speed that these objects experience, lending evidence to suggestions some years ago by modelers (Jewitt & Luu, published in 1996) that a competition between collisional resurfacing and radiation reddening may contribute to the color diversity of KBOs.