A first assessment of the strength of cometary particles collected in-situ by the COSIMA instrument onboard ROSETTA

Soon after the arrival of the ROSETTA spacecraft at Comet 67/P Churyumov-Gerasimenko the onboard instrument COSIMA (“Cometary Secondary Ion Mass Analyzer”) collected a large number of cometary dust particles on targets from gold black of thickness between 10 and 30 μm. Inspection by its camera subsystem revealed that many of them consist of smaller units of typically some tens of micrometers in size. The collection process left the smaller dust particles in an essentially unaltered state whereas most particles larger than about 100 μm got fragmented into smaller pieces. Using the observed fragment size distributions, the present paper includes a first assessment of the strength for those dust particles that were disrupted upon impact

Characterization of the refractory organic matter present in the dust particles of 67P/Churyumov-Gerasimenko.

International audienceThe Cometary Secondary Ion Mass Analyser (COSIMA), a miniaturized time-of-flight secondary ion mass spectrometer (ToF-SIMS), is one of the dust particle instruments onboard the orbiter of the Rosetta mission that arrived to comet 67P/Churyumov-Gerasimenko in mid-2014. COSIMA analyses the mineral and organic composition of dust particles that are captured on metal targets exposed to space [1, 2]. The mass spectra acquired by COSIMA show that refractory organic matter is ubiquitous in cometary dust particles [2]. The nature of this carbonaceous material will be discussed. We will highlight the abundance of organic matter in these dust particles as well as the nitrogen to carbon elemental ratio of this refractory organic matter. These results obtained on the dust particles of 67P will be compared to those from other astrophysical objects (carbonaceous chondrites, IDPs, micro-meteorites). This comparison could provide clues on the origin and evolution of the cometary organic matter. References: [1] Hilchenbach, M. et al. (2016) ApJ, 816, L32. [2] Schulz, R. et al. (2015) Nature, 518, 216-218. [3] Fray, N. et al. (2016) Nature, 538, 72-74

Characterization of the refractory organic matter present in the dust particles of 67P/Churyumov-Gerasimenko.

International audienceThe Cometary Secondary Ion Mass Analyser (COSIMA), a miniaturized time-of-flight secondary ion mass spectrometer (ToF-SIMS), is one of the dust particle instruments onboard the orbiter of the Rosetta mission that arrived to comet 67P/Churyumov-Gerasimenko in mid-2014. COSIMA analyses the mineral and organic composition of dust particles that are captured on metal targets exposed to space [1, 2]. The mass spectra acquired by COSIMA show that refractory organic matter is ubiquitous in cometary dust particles [2]. The nature of this carbonaceous material will be discussed. We will highlight the abundance of organic matter in these dust particles as well as the nitrogen to carbon elemental ratio of this refractory organic matter. These results obtained on the dust particles of 67P will be compared to those from other astrophysical objects (carbonaceous chondrites, IDPs, micro-meteorites). This comparison could provide clues on the origin and evolution of the cometary organic matter. References: [1] Hilchenbach, M. et al. (2016) ApJ, 816, L32. [2] Schulz, R. et al. (2015) Nature, 518, 216-218. [3] Fray, N. et al. (2016) Nature, 538, 72-74

Characterization of the refractory organic matter present in the dust particles of 67P/Churyumov-Gerasimenko.

International audienceThe Cometary Secondary Ion Mass Analyser (COSIMA), a miniaturized time-of-flight secondary ion mass spectrometer (ToF-SIMS), is one of the dust particle instruments onboard the orbiter of the Rosetta mission that arrived to comet 67P/Churyumov-Gerasimenko in mid-2014. COSIMA analyses the mineral and organic composition of dust particles that are captured on metal targets exposed to space [1, 2]. The mass spectra acquired by COSIMA show that refractory organic matter is ubiquitous in cometary dust particles [2]. The nature of this carbonaceous material will be discussed. We will highlight the abundance of organic matter in these dust particles as well as the nitrogen to carbon elemental ratio of this refractory organic matter. These results obtained on the dust particles of 67P will be compared to those from other astrophysical objects (carbonaceous chondrites, IDPs, micro-meteorites). This comparison could provide clues on the origin and evolution of the cometary organic matter. References: [1] Hilchenbach, M. et al. (2016) ApJ, 816, L32. [2] Schulz, R. et al. (2015) Nature, 518, 216-218. [3] Fray, N. et al. (2016) Nature, 538, 72-74

Characterization of the refractory organic matter present in the dust particles of 67P/Churyumov-Gerasimenko.

International audienceThe Cometary Secondary Ion Mass Analyser (COSIMA), a miniaturized time-of-flight secondary ion mass spectrometer (ToF-SIMS), is one of the dust particle instruments onboard the orbiter of the Rosetta mission that arrived to comet 67P/Churyumov-Gerasimenko in mid-2014. COSIMA analyses the mineral and organic composition of dust particles that are captured on metal targets exposed to space [1, 2]. The mass spectra acquired by COSIMA show that refractory organic matter is ubiquitous in cometary dust particles [2]. The nature of this carbonaceous material will be discussed. We will highlight the abundance of organic matter in these dust particles as well as the nitrogen to carbon elemental ratio of this refractory organic matter. These results obtained on the dust particles of 67P will be compared to those from other astrophysical objects (carbonaceous chondrites, IDPs, micro-meteorites). This comparison could provide clues on the origin and evolution of the cometary organic matter. References: [1] Hilchenbach, M. et al. (2016) ApJ, 816, L32. [2] Schulz, R. et al. (2015) Nature, 518, 216-218. [3] Fray, N. et al. (2016) Nature, 538, 72-74

Dust particle flux and size distribution in the coma of 67P/Churyumov-Gerasimenko measured in situ by the COSIMA instrument on board Rosetta

Context. The COmetary Secondary Ion Mass Analyzer (COSIMA) on board Rosetta is dedicated to the collection and compositional analysis of the dust particles in the coma of 67P/Churyumov-Gerasimenko (67P). Aims. Investigation of the physical properties of the dust particles collected along the comet trajectory around the Sun starting at a heliocentric distance of 3.5 AU. Methods. The flux, size distribution, and morphology of the dust particles collected in the vicinity of the nucleus of comet 67P were measured with a daily to weekly time resolution. Results. The particles collected by COSIMA can be classified according to their morphology into two main types: compact particles and porous aggregates. In low-resolution images, the porous material appears similar to the chondritic-porous interplanetary dust particles collected in Earth’s stratosphere in terms of texture. We show that this porous material represents 75% in volume and 50% in number of the large dust particles collected by COSIMA. Compact particles have typical sizes from a few tens of microns to a few hundreds of microns, while porous aggregates can be as large as a millimeter. The particles are not collected as a continuous flow but appear in bursts. This could be due to limited time resolution and/or fragmentation either in the collection funnel or few meters away from the spacecraft. The average collection rate of dust particles as a function of nucleo-centric distance shows that, at high phase angle, the dust flux follows a 1/d2comet law, excluding fragmentation of the dust particles along their journey to the spacecraft. At low phase angle, the dust flux is much more dispersed compared to the 1/d2comet law but cannot be explained by fragmentation of the particles along their trajectory since their velocity, indirectly deduced from the COSIMA data, does not support such a phenomenon. The cumulative size distribution of particles larger than 150 μm follows a power law close to r− 0.8 ± 0.1, confirming measurements made by another Rosetta dust instrument Grain Impact Analyser and Dust Accumulator (GIADA). The cumulative size distribution of particles between 30 μm and 150 μm has a power index of −1.9 ± 0.3. The excess of dust in the 10–100 μm  range in comparison to the 100 μm–1 mm range together with no evidence for fragmentation in the inner coma, implies that these particles could have been released or fragmented at the nucleus right after lift-off of larger particles. Below 30 μm, particles exhibit a flat size distribution. We interprete this knee in the size distribution at small sizes as the consequence of strong binding forces between the sub-constitutents. For aggregates smaller than 30 μm, forces stronger than Van-der-Waals forces would be needed to break them apart

Nitrogen-to-carbon atomic ratio measured by COSIMA in the particles of comet 67P/Churyumov–Gerasimenko

International audienceThe COmetary Secondary Ion Mass Analyzer (COSIMA) on board the Rosetta mission has analysed numerous cometary dust particles collected at very low velocities (a few m s(-1)) in the environment of comet 67P/Churyumov-Gerasimenko (hereafter 67P). In these particles, carbon and nitrogen are expected mainly to be part of the organic matter. We have measured the nitrogen-to-carbon (N/C) atomic ratio of 27 cometary particles. It ranges from 0.018 to 0.06 with an averaged value of 0.035 +/- 0.011. This is compatible with the measurements of the particles of comet 1P/Halley and is in the lower range of the values measured in comet 81P/Wild 2 particles brought back to Earth by the Stardust mission. Moreover, the averaged value found in 67P particles is also similar to the one found in the insoluble organic matter extracted from CM, CI and CR carbonaceous chondrites and to the bulk values measured in most interplanetary dust particles and micrometeorites. The close agreement of the N/C atomic ratio in all these objects indicates that their organic matters share some similarities and could have a similar chemical origin. Furthermore, compared to the abundances of all the detected elements in the particles of 67P and to the elemental solar abundances, the nitrogen is depleted in the particles and the nucleus of 67P as was previously inferred also for comet 1P/Halley. This nitrogen depletion could constrain the formation scenarios of cometary nuclei