Examinando por Autor "Agarwal, J."

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Acceso Abierto
Multidisciplinary analysis of the Hapi region located on Comet 67P/Churyumov–Gerasimenko
(Oxford Academics: Oxford University Press, 2019-05-07) Pajola, M.; Lee, J. C.; Oklay, N.; Hviid, S. F.; Penasa, L.; Mottola, S.; Shi, X.; Fornasier, S.; Davidsson, B. J. R.; Giacomini, L.; Lucchetti, A.; Massironi, M.; Vicent, J. B.; Bertini, I.; Naletto, G.; Ip, W. H.; Sierks, H.; Lamy, Philippe; Rodrigo, Rafael; Koschny, D.; Keller, H. U.; Agarwal, J.; Barucci, M. A.; Bertaux, J. L.; Bodewits, D.; Cambianica, P.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; El Maarry, M. R.; Feller, C.; Ferrari, S.; Fulle, M.; Gutiérrez, Pedro J.; Güttler, C.; Lara, L. M.; La Forgia, F.; Lazzarin, M.; Lin, Z. Y.; López Moreno, J. J.; Marzari, F.; Preusker, F.; Scholten, F.; Toth, I.; Tubiana, C.; European Space Agency (ESA); Pajola, M. [0000-0002-3144-1277]; Penasa, L. [0000-0002-6394-3108]; Fornasier, S. [0000-0001-7678-3310]; Lucchetti, A. [0000-0001-7413-3058]; Vicent, J. B. [0000-0001-6575-3079]; Naletto, G. [0000-0003-2007-3138]; Barucci, M. A. [0000-0002-1345-0890]; Bertaux, J. L. [0000-0003-0333-229X]; Deller, J. [0000-0001-8341-007X]; Fulle, M. [0000-0001-8435-5287]; Güttler, C. [0000-0003-4277-1738]; Tubiana, C. [0000-0001-8475-9898]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
By using the Rosetta/OSIRIS-NAC data set taken in 2014 August, we focus on the neck region, called Hapi, located on 67P Churyumov–Gerasimenko’s Northern hemisphere. The gravitational potential and slopes of Hapi, coupled with the geological unit identification and the boulder size–frequency distributions, support the interpretation that both taluses and gravitational accumulation deposits observable on Hapi are the result of multiple cliff collapses that occurred at different times. By contrast, the fine-particle deposits observable in the central part of the study area are made of aggregates coming from the Southern hemisphere and deposited during each perihelion passage. Both the consolidated terrains on the western part of Hapi, as well as the centrally aligned ridge made of boulder-like features, suggest that Hapi is in structural continuity with the onion-like structure of the main lobe of 67P. Despite the dusty blanket observable on Hapi, its terrains are characterized by water-ice-rich components that, once repeatedly and rapidly illuminated, sublimate, hence resulting in the strong jet activity observed in 2014 August.
Acceso Abierto
Seasonal variations in source regions of the dust jets on comet 67P/Churyumov-Gerasimenko
(EDP Sciences, 2019-09-20) Lai, I. L.; Ip, W. H.; Lee, J. C.; Lin, Z. Y.; Vicent, J. B.; Oklay, N.; Sierks, H.; Barbieri, C.; Lamy, Philippe; Rodrigo, Rafael; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, Pedro J.; Güttler, C.; Hofmann, M.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovács, G.; kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; López Moreno, J. J.; Marzari, F.; Naletto, G.; Shi, X.; Tubiana, C.; Thomas, N.; Ministry of Science and Technology, Taiwan (MOST)
Aims. We investigate the surface distribution of the source regions of dust jets on comet 67P/Churyumov-Gerasimenko as a function of time. Methods. The dust jet source regions were traced by the comprehensive imaging data set provided by the OSIRIS scientific camera. Results. We show in detail how the projected footpoints of the dust jets and hence the outgassing zone would move in consonance with the sunlit belt. Furthermore, a number of source regions characterized by repeated jet activity might be the result of local topographical variations or compositional heterogeneities. Conclusions. The spatial and temporal variations in source regions of the dust jets are influenced significantly by the seasonal effect. The strong dependence on the solar zenith angle and local time could be related to the gas sublimation process driven by solar insolation on a surface layer of low thermal inertia.
Acceso Abierto
The backscattering ratio of comet 67P/Churyumov–Gerasimenko dust coma as seen by OSIRIS onboard Rosetta
(Oxford Academics: Oxford University Press, 2019-01-22) Bertini, I.; La Forgia, F.; Fulle, M.; Tubiana, C.; Güttler, C.; Moreno, F.; Agarwal, J.; Muñoz, O.; Mottola, S.; Ivanovsky, S.; Pajola, M.; Lucchetti, A.; Petropoulou, V.; Lazzarin, M.; Rotundi, A.; Bodewits, D.; Frattin, E.; Toth, I.; Masoumzadeh, N.; Kovács, G.; Rinaldi, G.; Guirado, D.; Sierks, H.; Naletto, G.; Lamy, Philippe; Rodrigo, Rafael; Koschny, D.; Davidsson, B. J. R.; Barbieri, C.; Barucci, M. A.; Bertaux, J. L.; Cambianica, P.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Deller, J.; Ferrari, S.; Ferri, F.; Fornasier, S.; Gutiérrez, Pedro J.; Hasselmann, P. H.; Ip, W. H.; Keller, H. U.; Lara, L. M.; López Moreno, J. J.; Marzari, F.; Massironi, M.; Penasa, L.; Shi, X.; Fulle, M. [0000-0001-8435-5287]; Tubiana, C. [0000-0001-8475-9898]; Güttler, C. [0000-0003-4277-1738]; Pajola, M. [0000-0002-3144-1277]; Rinaldi, G. [0000-0002-2968-0455]; Naletto, G. [0000-0003-2007-3138]; Barucci, M. A. [0000-0002-1345-0890]; Bertaux, J. L. [0000-0003-0333-229X]; Deller, J. [0000-0001-8341-007X]; Fornasier, S. [0000-0001-7678-3310]; Penasa, L. [0000-0002-6394-3108]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Remote sensing observations of dust particles ejected from comets provide important hints on the intimate nature of the materials composing these primitive objects. The measurement of dust coma backscattering ratio, BSR, defined as the ratio of the reflectance at phase angle 0° and 30°, helps tuning theoretical models aimed at solving the inverse scattering problem deriving information on the nature of the ejected particles. The Rosetta/OSIRIS camera sampled the coma phase function of comet 67P, with four series acquired at low phase angles from 2015 January to 2016 May. We also added previously published data to our analysis to increase the temporal resolution of our findings. We measured a BSR in the range ∼ [1.7–3.6], broader than the range found in literature from ground-based observations of other comets. We found that during the post-perihelion phase, the BSR is systematically larger than the classical cometary dust values only for nucleocentric distances smaller than ∼100 km. We explain this trend in terms of a cloud of chunks orbiting the nucleus at distances <100 km ejected during perihelion and slowly collapsing on the nucleus over a few months because of the coma gas drag. This also implies that the threshold particle size for the dust phase function to become similar to the nucleus phase function is between 2.5 mm and 0.1 m, taking into account previous Rosetta findings.