The trans-Neptunian object size distribution at small sizes
Complejo Astronómico El Leoncito - CONICET and Universidad Nacional de San Juan, Av. España 1512 sur, J5402DSP - San Juan, Argentina e-mail: email@example.com
2 Instituto de Astrofísica de Canarias, c/vía Láctea s/n, E38205, La Laguna, Tenerife, Spain
3 Fundación Galileo Galilei & Telescopio Nazionale Galileo, PO Box 565, 38700, S/C de La Palma, Tenerife, Spain
4 Institut d'Astrophysique Spatiale, Université Paris-Sud, bâtiment 121, 91405 Orsay Cedex, France
Accepted: 4 March 2009
Aims. The aim of this work is to estimate the size distribution of small Trans-Neptunian objects.
Methods. We simulate the irradiation and collisional processes affecting the surface of a Trans-Neptunian object for the first time using as a constraint the peculiar crystalline to amorphous water ice ratio observed on (136108) 2003 EL61.
Results. We find that the size distribution changes its exponent from at larger sizes to at the smaller ones, with a break radius of km. If this size distribution is applied to studying the collisional surface evolution of (136108) 2003 EL61, we find that the object must be covered by a thin ice crust of ≈0.12 cm, while the original composition of the object is still present at 1.61 cm or more below the surface. This result is not affected by a collision with a large projectile that occurred by chance more than 109 yr ago since after a short time the mean value obtained for the crystalline to amorphous water ice ratio is indistinguishable from the one obtained without a collision with a large projectile. Since the simulations are not sensitive to the effects of very small projectiles ( m), it is possible that the exponent of the size distribution for these very small objects changes again, approaching a Donhanyi's size distribution.
Key words: Kuiper Belt / solar system: formation / astrochemistry / methods: numerical
© ESO, 2009