Dust-dust collisions in cometary comas and their effect on size distributions
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Tuesday 9th
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Dust-dust collisions in cometary comas and their effect on size distributions
The mission of the European Space Agency, Rosetta, at comet 67P/Churyumov-Gerasimenko was the first space mission to measure a reliable dust size distribution in a comet and it was equipped with the instruments COSIMA, GIADA and MIDAS designed to study cometary dust. The radius of the aggregates collected by COSIMA was in the range between 7 and 150 microns with a differential size distribution which may be approximated by a power-law relationship. Assuming that the particles collected by COSIMA are pristine and neglecting fragmentation during collection, a power-law index characteristic of dust in protoplanetary disks would be expected. However, the differential size distribution of the dust particle flux suggests an index shallower than expected for large aggregates and a steeper one for small particles.
We apply our recently published Collision of Porous Aggregates (CPA) software in the COSIMA to study dust-dust collisional processes as the aggregates leave the nucleus and pass through the coma, and show that it influences the size distribution of ejected particles. We present the final distributions of mass, size and porosity of the dust population after a given number of random collisions between the aggregates and find good agreement between our results and the dust particle flux measured by COSIMA. Our results could be generalizable to other comets exhibiting comparable dust production patterns.