Fig. 3

image

Radii of the dust aggregates whose adhesion can be overcome by the gas pressure (see Eqs. (2) and (3)) and which are able to escape from the gravity field of the nucleus (see Eq. (4)) of comet 67P/Churyumov-Gerasimenko as a function of heliocentric distance. The different blue colors denote the size range of the dust aggregates that are able to escape from the comet in case of outgassing of H2O ice, CO2 ice, and CO ice. The calculations are performed for a radius of the nucleus of 2 km (Lowry et al. 2012), an albedo of 0.04, and a density of 470 kg m-3 (Sierks et al. 2015). For comparison, the three particle populations (indicated by the numbers 1 to 3; see main text for details) measured by the Grain Impact Analyzer and Dust Accumulator (GIADA) and the OSIRIS Narrow Angle Camera (NAC) are shown by the dashed-dotted box and the dotted boxes (Rotundi et al. 2015). The smallest particle size of population 3 is 28 μm and is not shown in this figure). To derive the smallest aggregate size, we used a constant ice temperature that was determined by the exact thermophysical model at 1 AU for H2O ice (208.4 K; see caption of Fig. 1), at 2 AU for CO2 ice (117.2 K), and at 3 AU for CO ice (33.9 K; these positions are indicated by the stars).

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