The activity of main belt comets

Abstract

Context. Main belt comets represent a recently discovered class of objects. They are quite intriguing because, while having a Tisserand invariant value higher than 3, are showing cometary activity. Aims. We study the activity of the main belt comets making the assumption that they are icy-bodies and that the activity has been triggered by an impact. We try to determine the characteristics of this activity. We also try to determine if the nowadays impact rate in the main asteroid belt is compatible with the hypothesis of an activity triggered by a recent impact. Methods. Due to the fact that the main belt comets can be considered as a kind of comets, we apply a thermal evolution model developed for icy bodies in order to simulate their activity. We also apply a model to derive the impact rate, with respect to the size of the impactor, in the main belt. Results. We demonstrate that a stable activity can result from a recent impact, able to expose ice-rich layers, and that the impact rate in the main belt is compatible with this explanation.

The Main Belt Comets and ice in the Solar System

“…From these results, they infer that in order for 133P to be active today, an impact must have occurred, by which material was removed from the surface to expose ice-rich layers. This idea is consistent with the study of Capria et al (2012) who found that impact rates in the MB are consistent with MBC activity being the result of impacts able to expose water ice at the surface of asteroids.…”

Main Belt Comets: A new class of small bodies in the solar system

“…The dust is left behind when ice sublimates and thus a dust mantle forms and grows very slowly with repeated perihelion passages, with not uniform thickness over the surface. Similar conclusions were reached by Capria et al (2010), who suggested that the activity of MBCs is due to a recent collision with a small body and that we are probably in the presence of a cratering event. The authors also estimated that a 5-km sized asteroid has an average lifetime of 2.2 Gyr, implying the observed MBCs are not primordial but rather fragments produced by collisional evolution.…”

P/2006 VW139: a main-belt comet born in an asteroid collision?

“…Wherever MBCs originate from, their activity, although still not reliably understood, is likely triggered by the impact excavation of subsurface ice (Hsieh, Jewitt & Fernández 2004; Jewitt 2012) because completely exposed surface ice is unstable against sublimation at their heliocentric distances over Gyr time‐scales. According to Hsieh (2009) and Capria et al (2012), this hypothesis is in reasonable agreement with the present‐day impact frequency in the main belt.…”