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| Titel |
Dust Measurements in the Coma of Comet 67P/Churyumov-Gerasimenko Inbound to the Sun Between 3.7 and 3.4 AU |
| VerfasserIn |
Alessandra Rotundi, Vincenzo Della Corte, Marco Fulle, Marco Ferrari, Roberto Sordini, Stavro Ivanovski, Mario Accolla, Francesca Lucarelli, Vladimir Zakharov, Elena Mazzotta Epifani, José J. López-Moreno, Julio Rodríguez, Luigi Colangeli, Pasquale Palumbo, Ezio Bussoletti, Jean-Francois Crifo, Francesca Esposito, Simon F. Green, Eberhard Grün, Philippe L. Lamy |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112734
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| Publikation (Nr.) |
 EGU/EGU2015-12907.pdf |
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| Zusammenfassung |
| (21) ESA-ESAC, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spagna, (22) Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany, (23) Center of Studies and Activities for Space (CISAS), University of Padova, I-35131 Padova, Italy, (24) Department of Physics and Astronomy, University of Padova, I-35131 Padova, Italy
Comets are the most primitive bodies in the solar system. They retain a cosmo-chemical record of conditions in the solar nebula when the planets were forming, 4.5 billion years ago. While accurate measurements of the gas loss rate from comets are possible under favorable conditions even from Earth, estimates of the dust loss rate so far have been much more uncertain. Multi-parametric models are needed to extract global dust parameters from the dust features of comets (e.g. coma, tails and trails) observed from ground and Earth orbiting telescopes, and it is often difficult to establish the uniqueness of these model results.
Critical measurements for understanding the process of accretion and the refractory to volatiles ratio in the solar nebula are being obtained by the Grain Impact Analyzer and Dust Accumulator (GIADA) experiment onboard ESA’s Rosetta spacecraft, now orbiting comet 67P/Churyumov-Gerasimenko (67P/CG). GIADA measures the mass, momentum and velocity of individual grains, providing the dust loss rate over three orders of magnitude in mass for grains from tens to hundreds of microns in diameter. GIADA consists of three subsystems: 1) the Grain Detection System (GDS) to detect dust grains as they pass through a laser curtain, 2) the Impact Sensor (IS) to measure grain momentum derived from the impact on a plate connected to five piezoelectric sensors, and 3) the Mi-croBalances System (MBS); five quartz crystal microbalances in roughly orthogonal directions providing the cumu-lative dust flux of grains smaller than 10 microns. GDS provides data on grain speed and its optical cross section. The IS grain momentum measurement, when combined with the GDS detection time, provides a direct measurement of grain speed and mass. These combined measurements characterize single grain dust dynamics in the coma of 67P/CG.
The first grain was detected on 1 August 2014 at 814 km from the comet nucleus. Between then and 13 Septem-ber 2014 GIADA detected 35 grains ranging in mass from ~ 5 x 10-10 to 8 x 10-8 kg. Including complementary data from the OSIRIS narrow angle camera, the dust mass loss was calculated over an additional three orders of magni-tude in mass, extending the ejected dust grain sizes up to 2 cm. Combined with data from the MIRO and the ROSINA instruments onboard Rosetta we find a dust/gas mass ratio of 4 +/- 2 averaged over the sunlit nucleus sur-face. The dust to gas ratio may change as the comet approaches closer to the Sun.
Acknowledgments: GIADA was built by a consortium led by the Univ. Napoli “Parthenope” & INAF- Oss. Astr. Capodimonte, in collabo-ration with the Inst. de Astrofisica de Andalucia, Selex-ES, FI and SENER. GIADA is presently managed & operated by Ist. di Astrofisica e Planetologia Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale Italiana, IT, with the support of the Spanish Ministry of Education and Science MEC, ES. GIADA was developed from a PI proposal from the University of Kent; sci. & tech. contribution were pro-vided by CISAS, IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We thank the RSGS/ESAC,
RMOC/ESOC & Rosetta Project/ESTEC for their outstanding work. Science support provided was by NASA through the US Rosetta Project managed by the Jet Propulsion Laboratory/California Institute of Technology. GIADA calibrated data will be available through ESA’s PSA web site(www.rssd.esa.int/index.php?project=PSA&page=in dex). We would like to thank Angioletta Coradini for her contribution as a GIADA Co-I. We thank the MIRO, OSIRIS and ROSINA teams for sharing their early results with us. |
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