Why did Comet 17P/Holmes burst out?

TL;DR

This study explains Comet 17P/Holmes's outburst through sublimation of water ice beneath a dust cover, highlighting the comet's porous structure and variable molecular composition, with implications for its mass loss.

Contribution

It introduces a model linking the outburst to sublimation processes beneath a dust cover, emphasizing the comet's porous interior and variable molecular abundances.

Findings

The outburst was caused by sublimation breaking the dust cover.

The comet lost about 3% of its mass during the event.

The sublimating surface area was much larger than the nucleus surface.

Abstract

Based on millimeter-wavelength continuum observations we suggest that the recent 'spectacle' of comet 17P/Holmes can be explained by a thick, air-tight dust cover and the effects of H2O sublimation, which started when the comet arrived at the heliocentric distance <= 2.5 AU. The porous structure inside the nucleus provided enough surface for additional sublimation, which eventually led to the break up of the dust cover and to the observed outburst. The magnitude of the particle burst can be explained by the energy provided by insolation, stored in the dust cover and the nucleus within the months before the outburst: the subliming surface within the nucleus is more than one order of magnitude larger than the geometric surface of the nucleus -- possibly an indication of the latter's porous structure. Another surprise is that the abundance ratios of several molecular species with respect to H2O are variable. During this apparition, comet Holmes lost about 3% of its mass, corresponding to a 'dirty ice' layer of 20m.