Volcanoes on Quaoar?

摘要

Quaoar, a large body in the Kuiper belt, has crystalline water ice on its surface, yet conditions there should favour amorphous ice. Does this mean that resurfacing has taken place — perhaps even volcanism? Our planetary system does not end at Pluto. Hundreds of bodies exist in the Kuiper belt, which extends outwards from Pluto, sharing the same plane as the planetary orbits. The largest known bodies in the Kuiper belt are not much smaller than Pluto, and some have similar dynamics to that planet. Although the existence of the Kuiper belt had long been hypothesized, the first Kuiper-belt body was discovered only in 1992, by Jewitt and Luu. These same authors now propose that Quaoar, the largest known of these bodies, has crystalline water ice on its surface and possibly also ammonia (see page 731 of this issue). The presence of crystalline ice is surprising, because it is widely believed that its formation requires a temperature of around 100 K or more — substantially higher than the surface temperature of these bodies. The precise temperature required, however, is not known and may not be the same in laboratory experiments as it is in space. Yet it might be that we are seeing evidence for 'planetary' processes such as volcanism within these bodies.