Seasonal exposure of carbon dioxide ice on the nucleus of comet 67P/Churyumov-Gerasimenko

Filacchione, G.; Raponi, A.; Capaccioni, F.; Ciarniello, M.; Tosi, F.; Capria, M. T.; Sanctis, M. C. De; Migliorini, A.; Piccioni, G.; Cerroni, P.; Barucci, Maria Antonella; Fornasier, S.; Schmitt, Bernard; Quirico, E.; Erard, S.; Bockelée‐Morvan, Dominique; Leyrat, C.; Arnold, Gabriele; Mennella, V.; Ammannito, E.; Bellucci, G.; Benkhoff, J.; Bibring, Jean‐Pierre; Blanco, A.; Błęcka, M. I.; Carlson, R. W.; Carsenty, U.; Colangeli, L.; Combes, M.; Combi, M. R.; Crovisier, J.; Drossart, P.; Encrenaz, Thérèse; Federico, C.; Fink, Uwe; Fonti, S.; Fulchignoni, M.; Ip, W.-H.; Irwin, P.; Jaumann, R.; Kuehrt, E.; Langevin, Y.; Magni, G.; McCord, T. B.; Moroz, L. V.; Mottola, S.; Palomba, E.; Schade, U.; Stephan, K.; Taylor, F. W.; Tiphéne, D.; Tozzi, G. P.; Beck, Pierre; Biver, Nicolás; Bonal, L.; Combe, J. Ph.; Despan, Daniela; Flamini, E.; Formisano, M.; Frigeri, Alessandro; Grassi, D.; Gudipati, Murthy S.; Kappel, David; Longobardo, A.; Mancarella, F.; Markus, Kathrin; Merlin, F.; Orosei, R.; Rinaldi, G.; Cartacci, M.; Cicchetti, A.; Hello, Y.; Henry, Florence; Jacquinod, S.; Réess, Jean-Michel; Noschese, R.; Politi, R.; Peter, G.

doi:10.1126/science.aag3161

Cited by 70 publications

(49 citation statements)

References 37 publications

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“…As mentioned before, volatile exposures in the Anhur region were reported since the first observations (Filacchione et al, 2016a;Fornasier et al, 2016Fornasier et al, , 2017 when the comet was ∼ 2 au inbound. However, frost persisting inside the canyon-like structure was first observed in April 2016 and is clearly evident in the high-resolution images acquired during June-July 2016 ( Figs.…”

Section: Discussionmentioning

confidence: 66%

“…i) The first detection of CO 2 ice at the boundary between the Anhur and Bes regions (located at lon=66.06 o and lat=-54.56 o ) on 21-22 March 2015, when the southern hemisphere started to be illuminated by the Sun after its long cometary winter. This 80×60 m 2 area was estimated to contain about 57 kg of carbon dioxide, corresponding to a 9 cm thick layer (Filacchione et al, 2016a). ii) The detection of two bright patches of exposed water ice, the largest observed by Rosetta (more than 1500 m 2 each), on 27 April 2015, which survived for at least 10 days: one located in the same position as the CO 2 ice detection, and the other centered at lon = 76.45 • and lat = -54.15 • , in the Bes region, but very close to the boundary with Anhur.…”

Section: Evidence Of Frost and Exposed Water Icementioning

confidence: 99%

“…Two extended bright patches (of about 1500 m 2 each) of exposed water ice were identified at the end of April 2015, surviving for at least ten days . One of these (at the boundary between the Anhur and Bes regions) also included the first and so far only detection of CO 2 ice, which was observed with the Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) (Filacchione et al, 2016a) in March 2015. The observations of different ices clearly point to a more pristine area where different volatiles are exposed.…”

Section: Introductionmentioning

confidence: 99%

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Surface evolution of the Anhur region on comet 67P/Churyumov-Gerasimenko from high-resolution OSIRIS images

Fornasier

Feller

Hasselmann

et al. 2019

A&A

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Context. The southern hemisphere of comet 67P/Churyumov-Gerasimenko (67P) became observable by the Rosetta mission in March 2015, a few months before cometary southern vernal equinox. The Anhur region in the southern part of the comet's larger lobe was found to be highly eroded, enriched in volatiles, and highly active. Aims. We analyze high-resolution images of the Anhur region pre-and post-perihelion acquired by the OSIRIS imaging system on board the Rosetta mission. The Narrow Angle Camera is particularly useful for studying the evolution in Anhur in terms of morphological changes and color variations.Methods. Radiance factor images processed by the OSIRIS pipeline were coregistered, reprojected onto the 3D shape model of the comet, and corrected for the illumination conditions. Results. We find a number of morphological changes in the Anhur region that are related to formation of new scarps; removal of dust coatings; localized resurfacing in some areas, including boulders displacements; and vanishing structures, which implies localized mass loss that we estimate to be higher than 50 million kg. The strongest changes took place in and nearby the Anhur canyon-like structure, where significant dust cover was removed, an entire structure vanished, and many boulders were rearranged. All such changes are potentially associated with one of the most intense outbursts registered by Rosetta during its observations, which occurred one day before perihelion passage. Moreover, in the niche at the foot of a new observed scarp, we also see evidence of water ice exposure that persisted for at least six months. The abundance of water ice, evaluated from a linear mixing model, is relatively high (> 20%). Our results confirm that the Anhur region is volatile-rich and probably is the area on 67P with the most pristine exposures near perihelion.

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Section: Discussionmentioning

confidence: 66%

Section: Evidence Of Frost and Exposed Water Icementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surface evolution of the Anhur region on comet 67P/Churyumov-Gerasimenko from high-resolution OSIRIS images

Fornasier

Feller

Hasselmann

et al. 2019

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“…The presence of CO 2 ice in the these regions of the Southern hemisphere and in the same period is not unexpected, since VIRTIS detected a CO 2 -ice rich area in the Anhur region at the end of March 2015 (Filacchione et al 2016b). On the Southern hemisphere, the CO 2 ice is generally closer to the surface, thus more accessible.…”

Section: Azimuthal Gas and Dust Distributionmentioning

confidence: 73%

Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

Tubiana

Rinaldi

Güttler

et al. 2019

A&A

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Context. On 27 April 2015, when 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving towards perihelion, the OSIRIS and VIRTIS-M instruments on board Rosetta simultaneously observed the evolving dust and gas coma during a complete rotation of the comet. Aims. We aim to characterize the dust, H 2 O and CO 2 gas spatial distribution in the inner coma. To do this we performed a quantitative analysis of the release of dust and gas and compared the observed H 2 O production rate with the one calculated using a thermo-physical model. Methods. For this study we selected OSIRIS WAC images at 612 nm (dust) and VIRTIS-M image cubes at 612 nm, 2700 nm (H 2 O emission band) and 4200 nm (CO 2 emission band). We measured the average signal in a circular annulus, to study spatial variation around the comet, and in a sector of the annulus, to study temporal variation in the sunward direction with comet rotation, both at a fixed distance of 3.1 km from the comet centre.Results. The spatial correlation between dust and water, both coming from the sun-lit side of the comet, shows that water is the main driver of dust activity in this time period. The spatial distribution of CO 2 is not correlated with water and dust. There is no strong temporal correlation between the dust brightness and water production rate as the comet rotates. The dust brightness shows a peak at 0 • sub-solar longitude, which is not pronounced in the water production. At the same epoch, there is also a maximum in CO 2 production. An excess of measured water production, with respect to the value calculated using a simple thermo-physical model, is observed when the head lobe and regions of the Southern hemisphere with strong seasonal variations are illuminated (sub-solar longitude 270 • -50 • ). A drastic decrease in dust production, when the water production (both measured and from the model) displays a maximum, happens when typical Northern consolidated regions are illuminated and the Southern hemisphere regions with strong seasonal variations are instead in shadow (sub-solar longitude 50 • -90 • ). Possible explanations of these observations are presented and discussed.

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“…2, showing the dust continuum at 1.1 μm, and the water vapour and CO 2 band intensities for a sequence of three VIRTIS-M images: o, p and q, as reported in Table 1. be able to evaporate CO 2 ice because it is freshly exposed on the comet's surface. In fact, observations of the southern hemisphere in the Anhur region have now revealed patches of exposed CO 2 ice on the surface (Filacchione et al 2016).…”

Section: The April 27 Data Setmentioning

confidence: 99%

Properties of the dust in the coma of 67P/Churyumov-Gerasimenko observed with VIRTIS- M

Rinaldi

Fink

Doose

et al. 2016

Mon. Not. R. Astron. Soc.

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Seasonal exposure of carbon dioxide ice on the nucleus of comet 67P/Churyumov-Gerasimenko

Cited by 70 publications

References 37 publications

Surface evolution of the Anhur region on comet 67P/Churyumov-Gerasimenko from high-resolution OSIRIS images

Surface evolution of the Anhur region on comet 67P/Churyumov-Gerasimenko from high-resolution OSIRIS images

Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

Properties of the dust in the coma of 67P/Churyumov-Gerasimenko observed with VIRTIS- M

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