Activity of comet 103P/Hartley 2 at the time of the EPOXI mission fly-by

TL;DR

This study analyzes the activity of comet 103P/Hartley 2 during the EPOXI fly-by, linking ground and spacecraft observations to characterize the grains produced, their composition, and their behavior.

Contribution

It provides new insights into the solid component produced by the comet's activity, including grain lifetime and composition, based on combined ground and spacecraft data.

Findings

Grain lifetime of about 5 hours consistent with spacecraft observations

Grains from one active region have a very red color, indicating organics

Strong activity correlated with nucleus rotation

Abstract

Comet 103P/Hartley~2 was observed on Nov. 1-6, 2010, coinciding with the fly-by of the space probe EPOXI. The goal was to connect the large scale phenomena observed from the ground, with those at small scale observed from the spacecraft. The comet showed strong activity correlated with the rotation of its nucleus, also observed by the spacecraft. We report here the characterization of the solid component produced by this activity, via observations of the emission in two spectral regions where only grain scattering of the solar radiation is present. We show that the grains produced by this activity had a lifetime of the order of 5 hours, compatible with the spacecraft observations of the large icy chunks. Moreover, the grains produced by one of the active regions have a very red color. This suggests an organic component mixed with the ice in the grains.