A POSSIBLE LONG-LIVED BELT OF OBJECTS BETWEEN URANUS AND NEPTUNE

Recent discoveries of objects orbiting beyond Neptune(1-5) have emphas ized that our understanding of the distribution and dynamics of materi al in the outer Solar System is very incomplete. This trans-neptunian population-known as the Kuiper belt-is thought to act as a relatively stable reservoir of objects that could become short-period comets(6-9) , although there may be other regions of stability in the outer Solar System that could also supply such comets. Here I use numerical simula tions to identify one such long-lived region between the orbits of Ura nus and Neptune. I show that in the region 24-27 AU from the Sun, abou t 0.3 per cent of an initial population of small bodies moving on low- eccentricity, low-inclination orbits could survive for the age of the Solar System. The actual existence of this hypothetical belt is not pr ecluded by currently available observational Limits, and there could b e as much as similar to 5 x 10(-4) Earth masses of material populating this region-comparable to the mass of the asteroid belt between Mars and Jupiter.