Evidence of sub-surface energy storage in comet 67P from the outburst of 2016 July 03
Publication date: 26 October 2017
Authors: Agarwal. J., et al.
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 469
Issue: Suppl_2
Page: s606–s625
Year: 2017
Copyright: © 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
On 2016 July 03, several instruments onboard ESA's Rosetta spacecraft detected signs of an outburst event on comet 67P, at a heliocentric distance of 3.32 au from the Sun, outbound from perihelion. We here report on the inferred properties of the ejected dust and the surface change at the site of the outburst. The activity coincided with the local sunrise and continued over a time interval of 14–68 min. It left a 10-m-sized icy patch on the surface. The ejected material comprised refractory grains of several hundred microns in size, and sub-micron-sized water ice grains. The high dust mass production rate is incompatible with the free sublimation of crystalline water ice under solar illumination as the only acceleration process. Additional energy stored near the surface must have increased the gas density. We suggest a pressurized sub-surface gas reservoir, or the crystallization of amorphous water ice as possible causes.
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