Recent fluffy dust observations by Rosetta / GIADA and OSIRIS results
Abstract
During the 18 months of ongoing operations of ESA Rosetta Mission at comet 67P, the GIADA dust detector on-board the Rosetta orbiter has observed tens of showers of hundreds of mm-sized particles lasting a few seconds each. These particles had always a momentum below the detection threshold and speeds below 0.1 m/s. During campaigns investigating the source of false stars affecting the performance of Rosetta star-trackers, the OSIRIS Wide-Angle Camera has as well detected showers of mm-sized dust floating close to the spacecraft at speeds of a few cm/s. The observed low speeds, much lower than the escaping velocity from 67P nucleus, imply a strong dust deceleration at the spacecraft, possibly by its negative potential, which charges and fragments cm-sized fluffy parents of very low density (possibly close to 1 kg per cubic meter). The spacecraft electric field decelerates the approaching charged fragments, which are then accelerated away from the spacecraft in all the directions. This continuously replenished cloud of fluffy fragments, much denser than the surrounding dust coma, may be the source of Rosetta star-tracker issues, and should drive the software of star-trackers of future cometary missions. The presence of extremely fluffy particles in 67P nucleus puts strong constraints on the accretion history of the nuclei of the Jupiter Family Comets.
- Publication:
-
41st COSPAR Scientific Assembly
- Pub Date:
- July 2016
- Bibcode:
- 2016cosp...41E.634F