The dust and gas environment of comet 8P/Tuttle

Abstract

ABSTRACT Comet 8P/Tuttle has been selected as a possible backup target for the Comet Interceptor mission (ESA). This comet was observed intensively during its previous perihelion passage, in 2008 January. From those observations, important information was obtained about the physical properties of the nucleus and coma. This study focuses on the coma of 8P/Tuttle using visible spectra and images to derive gas and dust production rates. The production rates obtained suggest that this comet can be considered as ‘typical’ concerning the C2/CN and C3/CN ratios, although, depending on the criteria adopted, it could be defined as C3 depleted. NH2 production rates suggest an enrichment of this molecule. Visible and infrared images have been analysed using a Monte Carlo dust tail model. At comparatively large heliocentric distances, the coma is characterized by a dust-to-water ratio around or less than 1. Nevertheless, when the comet approaches perihelion, and the subsolar latitude crosses the equator, the coma dust-to-water ratio increases significantly, reaching values larger than six. Such a high dust-to-gas ratio around perihelion suggests that the nucleus of 8P/Tuttle is also ‘typical’ regarding the refractory content, considering the comparatively high values of that magnitude estimated for different comets.