Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun

Abstract

Critical measurements for understanding accretion and the dust/gas ratio in the solar nebula, where planets were forming 4.5 billion years ago, are being obtained by the GIADA (Grain Impact Analyser and Dust Accumulator) experiment on the European Space Agency's Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between 3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) detected 35 outflowing grains of mass 10(-10) to 10(-7) kilograms, and 48 grains of mass 10(-5) to 10(-2) kilograms, respectively. Combined with gas data from the MIRO (Microwave Instrument for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio of 4 ± 2 averaged over the sunlit nucleus surface. A cloud of larger grains also encircles the nucleus in bound orbits from the previous perihelion. The largest orbiting clumps are meter-sized, confirming the dust/gas ratio of 3 inferred at perihelion from models of dust comae and trails.

Density and Charge of Pristine Fluffy Particles From Comet 67p/Churyumov–gerasimenko

“…From 2014 August 1 to September 15, the Grain Impact Analyzer and Dust Accumulator (GIADA) instrument on board ESA's Rosetta Mission (Colangeli et al 2007;Della Corte et al 2014) collected compact particles, which constrained 67P's dust mass loss rate and dust/gas ratio at heliocentric distances >3.4 AU (Rotundi et al 2015). Up to 2015 January 14, GIADA has detected a total of 193 compact particles: 81 by both the GDS (laser curtain) and IS (impact sensor) subsystems (GDS+IS) and 112 by IS only.…”

“…No events with properties resembling the GDS-only showers have ever been observed in four years of clean-room tests on the GIADA ground model. Compact particles were identified as being formed by minerals processed in the pre-solar nebula which were accreted by comet 67P during formation in the Kuiper Belt and/or in the Uranus-Neptune zone (Rotundi et al 2015). The GDS-only detections, which are a factor of four more numerous, point to grains with physical properties completely different from those of compact particles.…”

GIADA performance during Rosetta mission scientific operations at comet 67P

“…GIADA detected the first dust particle on 1 August 2014 and since then it monitored the evolution of the 67P dust environment Fulle et al, 2015Fulle et al, , 2016aFulle et al, , 2016bGrün et al, 2016;Rotundi et al, 2015). During the mission, we monitored the functional parameters of the sensors, evaluating their health status and checking their performance over time and in different environmental conditions.…”

Distance determination method of dust particles using Rosetta OSIRIS NAC and WAC data

“…This knowledge will enhance the understanding of the evolution of comets. It is possible to measure the dust flux in the coma utilizing optical images as well as dust detectors (Fulle et al 2016, Rotundi et al 2015. Rosetta has been monitoring 67P from August 2014 to September 2016 from close vicinity.…”

“…Furthermore, it can be investigated if and how the distribution evolves in time, and the connection with the nucleus seasons. With detections of dust particles, collected between 3.6 and 3.4 AU inbound, it was possible to derive a dust size distribution for a large mass bin range (10 −10 − 10 −2 kg) (Fulle et al 2016, Rotundi et al 2015. The analysis was based on data from the GIADA instrument, see e.g.…”