The Dust Trail of Comet 67P/Churyumov-Gerasimenko

TL;DR

This study detects and analyzes the dust trail and nucleus of comet 67P/Churyumov-Gerasimenko using infrared and optical observations, estimating particle sizes, trail age, and impact probabilities relevant for the Rosetta mission.

Contribution

First infrared detection and analysis of comet 67P's dust trail, providing insights into particle sizes, trail age, and implications for spacecraft impact risk.

Findings

Dust trail detected in infrared but not optical images.

Trail particles are larger than 100 microns and at least one orbit old.

Estimated impact probability of trail grains with Rosetta is very low.

Abstract

We report the detection of comet 67P/Churyumov-Gerasimenko's dust trail and nucleus in 24 micron Spitzer Space Telescope images taken February 2004. The dust trail is not found in optical Palomar images taken June 2003. Both the optical and infrared images show a distinct neck-line tail structure, offset from the projected orbit of the comet. We compare our observations to simulated images using a Monte Carlo approach and a dynamical model for comet dust. We estimate the trail to be at least one orbit old (6.6 years) and consist of particles of size >~100 micron. The neck-line is composed of similar sized particles, particles of size but younger in age. Together, our observations and simulations suggest grains 100 micron and larger in size dominate the total mass ejected from the comet. The radiometric effective radius of the nucleus is 1.87 +/- 0.08 km, derived from the Spitzer observation. The Rosetta spacecraft is expected to arrive at and orbit this comet in 2014. Assuming the trail is comprised solely of 1 mm radius grains, we compute a low probability (~10^-3) of a trail grain impacting with Rosetta during approach and orbit insertion.