Letter to the Editor

Photophoresis as a source of hot minerals in comets

¹ Institut UTINAM, CNRS-UMR 6213, Observatoire de Besançon, BP 1615, 25010 Besançon Cedex, France e-mail: Olivier.Mousis@obs-besancon.fr
² Institute for Planetology, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
³ Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
⁴ Astronomy Group, Open University, Walton Hall, Milton Keynes MK76AA, UK

Received: 25 January 2007
Accepted: 24 February 2007

Abstract

A time-dependent model of the solar nebula is used to describe the outward transport of hot mineral aggregates from locations in the warm inner regions of the nebula under the influence of photophoresis. We show that there is a direct dependence between the size of the gap initially assumed to exist in the inner solar nebula and the heliocentric distance to which the aggregates are likely to drift. We demonstrate that, despite a significant contribution to the opacity of the disk resulting from Rayleigh scattering by hydrogen, photophoresis can be considered as a transport mechanism leading to the presence of hot minerals in comets. This mechanism can lead to an influx of hot minerals in the formation regions of the main cometary reservoirs, implying a potential “dust-loading” of bodies from these populations. This scenario is compatible with the detection of crystalline silicates in a growing number of comets and also with the recent identification of CAIs in the samples returned from Comet 81P/Wild 2 by the Stardust mission. Finally, we find that this mechanism is consistent with the compositional diversity observed in small bodies of the outer solar system, in contrast to other proposed processes which invoke an efficient turbulent mixing within the primordial nebula.