# Cometary dust collected by MIDAS on board Rosetta. I. Dust particle catalog and statistics

**Authors:** M. Kim, T. Mannel, P. D. Boakes, M. S. Bentley, A. Longobardo, H. Jeszenszky, R. Moissl, the MIDAS team  
**arXiv:** [2302.10721](https://arxiv.org/abs/2302.10721)  
**Date:** 2023-02-21  
**Summary page:** https://www.summarizepaper.com/en/paper/2302.10721v2/

## Key points

- The Rosetta mission studied the dust and gas environment of comet 67P/Churyumov-Gerasimenko.
- The Micro-Imaging Dust Analysis System (MIDAS) collected particles ranging from hundreds of nanometers to tens of micrometers and recorded their 3D topographic and textural information as well as statistical parameters.
- The revised MIDAS catalog includes 3523 particles in total, ranging from about 40 nm to about 8 μm in size.
- The study presents a detailed description of atomic force microscopy (AFM) images leading to more accurate identification and characterization of dust particles than previous catalogs had achieved before by carefully re-analyzing them resulting in addition more dust particles being included in this catalog along with a detailed description of their properties.
- Limitations associated with MIDAS include its inability to detect particles larger than one millimeter in size and how sizes and size distributions are expected to be influenced by fragmentation upon impact on collection targets during sampling operations.

## Summary

The Rosetta mission provided a unique opportunity to study the dust and gas environment of the inner coma of comet 67P/Churyumov-Gerasimenko. One of three in situ dust instruments on board, Micro-Imaging Dust Analysis System (MIDAS), collected particles with sizes ranging from hundreds of nanometers to tens of micrometers and recorded their 3D topographic and textural information as well as statistical parameters. The goal of this study is to present the revised MIDAS particle catalog, together with its main statistics and scientific results that can be extracted. The paper is organized into four sections: Section 2 provides a description of the MIDAS instrument and the mechanism of dust collection, including a sophisticated clustering algorithm to understand the fragmentation of dust particles during collection; Section 3 gives a general description of the MIDAS particle catalog and its main statistics, including size distributions of MIDAS particles and fragments, dust coverage maps, and clustering maps showing the distribution of fragments and parent particles; finally, Section 4 summarizes the findings. The revised MIDAS catalog includes 3523 particles in total, ranging from about 40 nm to about 8 μm in size. The mean value of equivalent radius derived from the 2D projection is 0.91 ± 0.79 μm while an improved equivalent radius based on particle volume coincides within uncertainties with a value of 0.56 ± 0.45 μm. The slope fitting for MIDAS particle size distribution yields an index b between -1.67 to -1.88 when using power law formula ar^b where r is equivalent radius or diameter depending on context. Furthermore, this study presents a detailed description of atomic force microscopy (AFM) images leading to more accurate identification and characterization of dust particles than previous catalogs had achieved before by carefully re-analyzing them resulting in addition more dust particles being included in this catalog along with a detailed description of their properties. The study also discusses limitations associated with MIDAS such as its inability to detect particles larger than one millimeter in size and how sizes and size distributions are expected to be influenced by fragmentation upon impact on collection targets during sampling operations.