Compacted aggregates from numerical simulations compared to Rosettacollected particles
Résumé
The Rosetta space mission includes three main instruments for solid dust particles analysis. The combinedmicroscope and mass spectrometer COSIMA (Cometary Secondary Ion Mass Analyser) [1], the atomic forcemicroscope MIDAS (Micro-Imaging Dust Analysis System) [2], and the impact detector GIADA (Grain ImpactAnalyser and Dust Accumulator) [3]. These three instruments provide complementary insights into the dustparticles properties thanks to their different approaches and resolution ranges (10nm to 1mm). GIADA andMIDAS observed a major contribution from compact dust aggregates together with a population of porousparticles with a low fractal dimension (Df ~ 1.7 for MIDAS [4]) [5, 6]. Such a fractal dust component of thenucleus and its properties give constraints on the formation of comets in the early solar system [5].In this work, we analyse results from a simple numerical model of dust aggregates compaction and compare themwith COSIMA images of collected aggregates to assess the initial physical properties of the dust populations. Weconsider 4 different kinds of fractal aggregates presenting different initial fractal dimensions (Df ~ 1.8/2.1/2.5/3)based on their aggregation processes (diffusion limited or reaction limited aggregations, depending on the surfacesticking probabilities of the monomers, and particle-cluster or cluster-cluster aggregations).We find that the aspect ratio distribution observed by COSIMA may be explained either by compacting twodifferent initial families with low and high fractal dimensions and the same cohesive strength between monomers,or by compacting a single type of particles (with an aggregation process like DLPA) however with a large rangeof internal cohesive strengths or collection velocities.References: [1] Kissel, J. et al. (2007) SSR, 128(1), 823-867. [2] Riedler, W. et al. (2007) SSR, 128(1-4),869-904. [3] Colangeli, L. et al. (2007) SSR, 128(1-4), 803-821. [4] Mannel, T. et al. (2016) MNRAS, 462(S1),304-311. [5] Fulle, M. and Blum, J. (2017), MNRAS, 469(S2), 39-44 [6] Fulle, M. et al. (2017) MNRAS 469(S2),45–49