Authors: Harold F. Levison & Alessandro Morbidelli.

Status: Scheduled to appear in the November 27, 2003 issue of Nature

This paper is embargoed until 1300 US Eastern Time on 26 November

Bold Paragraph: The 'dynamically cold Kuiper belt', which consists of objects on low inclination orbits between ~40 and 50AU from the Sun, currently contains less than 1/10 Earth-masses of material. This value is surprisingly low because, accordinging to accretion models, the objects observed there would not have grown to their present size unless the cold Kuiper belt originally contained tens of Earth-masses of solids. While several mechanisms have been proposed to produce the observed mass depletion, all have significant limitations. Here we show that the objects currently observed in the dynamically cold Kuiper belt were most likely formed interior to 35AU and were pushed outward by Neptune's 1:2 mean motion resonance during its final phase of migration. Combining our mechanism with previous works, we conclude that the entire Kuiper belt formed closer to the Sun and was transported outward during the final stages of planet formation.

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