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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.01.002 Byline: Michael Mueller (a), Alan W. Harris (a), Alan Fitzsimmons (b) Keywords: Asteroids; Infrared observations; Near-Earth objects; Spectrophotometry Abstract: The Amor-type near-Earth Asteroid (10302) 1989 ML has an 'Earth-like' orbit (period 1.44 yr, eccentricity 0.14, inclination 4.4[degrees]), therefore the energy required to reach it from the Earth is relatively small making it a very attractive target for rendezvous missions. We have observed 1989 ML in the thermal-infrared using the Spitzer Space Telescope, and compared these data with optical and near-infrared observations. The Spitzer results imply a diameter of 0.28[+ or -]0.05km and a geometric albedo of 0.37[+ or -]0.15; together with the reflectance spectrum they are consistent with the relatively rare E classification. Author Affiliation: (a) DLR Institute of Planetary Research, RutherfordstraAe 2, 12489 Berlin, Germany (b) Astrophysics Research Centre, Queen's University Belfast, BT7 1NN, UK Article History: Received 29 September 2006; Revised 18 December 2006

Our goal is to determine whether or not the observed sudden termination of the Edgeworth-Kuiper belt can he the result of perturbations from a hypothetical planet. We investigate the effects that such an object would produce on the primordial orbital distribution if the trans-neptunian objects, for a range of masses and orbital parameters of the hypothetical planet. In this numerical investigation, the motion of the hypothetical planet was influenced by the existing planets but not by its interaction with the disk. We find that no set of parameters produce results that match the observed data. Dynamical interaction with the disk is likely to be important so that the orbit of the hypothetical planet changes significantly during the integration interval. This is also discussed. The overall conclusion is that none of the models for the hypothetical planet that were investigated can reproduce the observed features of the Edgeworth-Kuiper belt starting from any probable primordial distribution. Keywords: Trans-neptunian objects: Planetary dynamics; Orbits; Origin, solar system

We examine possible locations for the primordial disk of the Edgeworth-Kuiper Belt (EKB), using several subsets of the known objects as markers of the total mass distribution. Using a secular perturbation theory, we find that the primordial plane of the EKB could have remained thin enough to escape detection only if it is clustered very closely about the invariable plane of the Solar System. Keywords: Transneptunian objects; Planetary dynamics; Orbits; Origin, Solar System