# Interpretation through experimental simulations of phase functions revealed by Rosetta in 67P dust coma

## TL;DR

This study compares the phase curves of comet 67P's dust with laboratory analogs, revealing that organic-rich, fluffy dust particles likely cause the observed u-shaped brightness phase curves.

## Contribution

It demonstrates that interplanetary dust analogs with specific composition and porosity can replicate the phase curves of comet 67P, linking dust properties to observed brightness features.

## Key findings

- Dust phase curves are similar between 67P and analogs.
- Organic compounds and fluffiness influence phase curve shape.
- Comet dust shares properties with zodiacal cloud particles.

## Abstract

Context: The dust-brightness phase curves that have been measured by the OSIRIS cameras on board the Rosetta spacecraft within the coma of comet 67P/Churyumov-Gerasimenko (67P) present a remarkable u-shape. Aims: Our goal is to compare these phase curves with those of tentatively analog dust samples to assess the key dust properties that might induce this shape. Methods: Light-scattering measurements have been made with the PROGRA2 instrument in the laboratory and in microgravity conditions on samples of different physical properties and compositions that are likely to be representative of cometary dust particles. Results: We find that the brightness phase curves of a series of interplanetary dust analogs that have been recently developed (to fit the polarimetric properties of the inner zodiacal cloud and their changes with heliocentric distance) are quite comparable to those of 67P. Key dust properties seem to be related to the composition and the porosity. Conclusions: We conclude that the shape of the brightness phase curves of 67P has to be related to the presence of a significant amount of organic compounds (at least 50% in mass) and of fluffy aggregates (of a size range of 10 to 200 microns). We also confirm similarities between the dust particles of this Jupiter-family comet and the particles within the inner zodiacal cloud.