| 1. |
|
|
| 2. |
- Grun, E., et al.
(författare)
-
The 2016 Feb 19 outburst of comet 67P/CG : an ESA Rosetta multi-instrument study
- 2016
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 462, s. S220-S234
-
Tidskriftsartikel (refereegranskat)abstract
- On 2016 Feb 19, nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in situ gas, dust and plasma instruments, and one dust collector. At 09: 40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50 per cent of the neutral gas density at Rosetta to factors > 100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors > 10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from similar to-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta ( 34 km from the nucleus): within 15 min the Star Tracker camera detected fast particles (similar to 25 m s(-1)) while 100 mu m radius particles were detected by the GIADA dust instrument similar to 1 h later at a speed of 6 m s(-1). The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined.
|
|
| 3. |
- Hilchenbach, M., et al.
(författare)
-
COMET 67P/CHURYUMOV-GERASIMENKO : CLOSE-UP on DUST PARTICLE FRAGMENTS
- 2016
-
Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing (IOPP). - 2041-8205 .- 2041-8213. ; 816:2
-
Tidskriftsartikel (refereegranskat)abstract
- The COmetary Secondary Ion Mass Analyser instrument on board ESA's Rosetta mission has collected dust particles in the coma of comet 67P/Churyumov-Gerasimenko. During the early-orbit phase of the Rosetta mission, particles and particle agglomerates have been imaged and analyzed in the inner coma at distances between 100 km and 10 km off the cometary nucleus and at more than 3 AU from the Sun. We identified 585 particles of more than 14 μm in size. The particles are collected at low impact speeds and constitute a sample of the dust particles in the inner coma impacting and fragmenting on the targets. The sizes of the particles range from 14 μm up to sub-millimeter sizes and the differential dust flux size distribution is fitted with a power law exponent of -3.1. After impact, the larger particles tend to stick together, spread out or consist of single or a group of clumps, and the flocculent morphology of the fragmented particles is revealed. The elemental composition of the dust particles is heterogeneous and the particles could contain typical silicates like olivine and pyroxenes, as well as iron sulfides. The sodium to iron elemental ratio is enriched with regard to abundances in CI carbonaceous chondrites by a factor from ∼1.5 to ∼15. No clear evidence for organic matter has been identified. The composition and morphology of the collected dust particles appear to be similar to that of interplanetary dust particles.
|
|
| 4. |
|
|
