Pebble formation by ice condensation

Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden

^a e-mail: katrin.ros@astro.lu.se

Abstract

Pebbles with sizes of centimeters to decimeters are needed in order to form kilometer-sized planetesimals, which in turn are needed for planet formation to proceed. The well-studied mechanism of coagulation is efficient only up to millimeter-sized dust grains. In this proceeding a numerical model of ice condensation as a complementary growth mechanism in turbulent protoplanetary discs is discussed. Close to an ice line, particles grow efficiently by ice condensation, which, combined with radial mixing, can supply a large extent of the disc with icy pebbles. Growth from millimeter-sized dust grains to at least decimeter-sized pebbles is possible on a time scale of only 10 000 years. The resulting particles are large enough to enable further growth into planetesimals via a variety of particle concentration mechanisms and subsequent gravitational collapse.