Comet 17P/Holmes: Possibility of a CO driven explosion

Abstract

Please cite this article as: Kossacki, K.J., Szutowicz, S., Comet 17P/Holmes: possibility of a CO driven explosion, Icarus (2011Icarus ( ), doi: 10.1016Icarus ( /j.icarus.2011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Comet AbstractThis work is a continuation of our previous paper about brightening of Comet 17P/Holmes (Kossacki and Szutowicz, 2010). In that paper we presented results of simulations indicating that the nonuniform crystallization of amorphous water ice itself is probably not sufficient for an explosion. In the present work we investigate the possibility that the explosion is caused by a rapid sublimation of the CO ice leading to the rise of gas pressure above the tensile strength of the nucleus. We simulated evolution of a model nucleus in the orbit of Comet 17P/Holmes. The nucleus is composed of water ice, carbon monoxide ice and dust and has the shape of an elongated ellipsoid. The simulations include crystallization of amorphous ice in the nucleus, changes of the dust mantle thickness, and sublimation of the CO ice. In our model CO is mantling grains composed of dust and amorphous water ice. Orientation of the nuclear spin axis in space is the same as derived in Moreno et al. (2008) for Comet Holmes during recent brightening event. Hence, the angle between the orbital and the equatorial planes of the comet is I = 95 o , and the cometocentric solar longitude at perihelion is Φ = 210 o . The calculations are performed for the south pole being the subsolar point close to time of the outburst. Our computations indicate, that the CO pressure within the comet nucleus can rise to high values. When the layer between the dust mantle and the crystallization front of the amorphous water ice is very fine grained, few microns in radius, the CO pressure within the nucleus can exceed 10 kPa. This value is the lowest estimate for the tensile strength of the nucleus of Comet Holmes (Reach et al., 2010). Hence, when the gas pressure reaches this value the nucleus may explode.

Location of upper borders of cavities containing dust and gas under pressure in comets

“…These estimates of the depth are in accordance with the depth (4–20 m) of the initial sublimation front of the CO ice in the models of the explosion of Comet 17P/Holmes considered by Kossacki & Szutowicz (2011). Our studies suggest that cavities containing dust and gas under pressure and located a few metres below the surfaces of comets can be common.…”

Lingering Grains of Truth Around Comet 17p/Holmes

“…A runaway exothermic phase transition of amorphous water ice to crystalline is probably insufficient to cause the outburst (Kossacki & Szutowicz 2010). If supervolatiles such as CO and/or CO 2 are trapped within the amorphous ice and heated sufficiently, the resulting gas production may be able to drive such activity, if the gas can build up sufficient internal pressure (Schleicher 2009;Sekanina 2009;Kossacki & Szutowicz 2011;Hillman & Prialnik 2012).…”

Comet 17p/Holmes: Contrast in Activity Between Before and After the 2007 Outburst

“…Several possible scenarios have been presented to explain the cause of the outburst; these include vaporization of pockets of more volatile ices such as CO 2 and CO (Schleicher 2009;Kossacki & Szutowicz 2011), the phase change of water from amorphous to crystalline ice (Sekanina 2009), thermal stress in the nucleus, or the polymerization of hydrogen cyanide (Gronkowski & Sacharczuk 2010). So far, according to our present knowledge of the physical and chemical structure of comets, CO inclusions are likely to be the most probable cause of Comet 17P/Holmes's outburst (Kossacki & Szutowicz 2010, 2011Gronkowski & Sacharczuk 2010).…”