1. The outer solar system

This year saw the final stages of surveys of the Kuiper Belt conducted by David Jewitt, Chad Trujillo, and Jane Luu at the Canada-France-Hawaii Telescope on Mauna Kea, Hawaii. Highlights include

• The publication of the results of the survey for scattered Kuiper Belt objects (those with semimajor axes $a \sim 100$ AU and high orbital excentricities). The Scattered Kuiper Belt population is found to contain $\sim 10^4$ objects with diameter $\geq 100$ km, and contribute a mass of ( $\sim 0.1 \, M_{\oplus}$). This is comparable in number and mass to the Kuiper Belt inside 50 AU.
• The detection of water ice in the Centaur 2060 Chiron (believed to be an ex-Kuiper Belt object). Based on this detection, Luu et al. predict that water ice is ubiquitous in objects originating in the Kuiper Belt, although its detectability depends on the fraction of the surface covered by the ice.
• The publication of an accretion model of KBOs that takes into account velocity evolution and fragmentation. The results indicate that the original Kuiper Belt was $\sim 100$ times more massive than it is now, containing a mass of order $10 \, M_{\oplus}$.