OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

Pommerol, Antoine; Thomas, Nicolas; Elmaarry, Mohamed Ramy; Pajola, M.; Groussin, O.; Auger, A. T.; Oklay, N.; Fornasier, S.; Feller, C.; Davidsson, B.; Gracia-Berna, A.; Jost, Bernhard; Marschall, Raphael; Poch, Olivier; Barucci, M. A.; Bertaux, J. L.; La Forgia, F.; Keller, H. U.; Kuehrt, E.; Lowry, S. C.; ... (2015). OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments. Astronomy and astrophysics, 583(A25), A25. EDP Sciences 10.1051/0004-6361/201525977

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Since OSIRIS started acquiring high-resolution observations of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, over one hundred meter-sized bright spots have been identified in numerous types of geomorphologic regions, but mostly located in areas receiving low insolation. The bright spots are either clustered, in debris fields close to decameter-high cliffs, or isolated without structural relation to the surrounding terrain. They can be up to ten times brighter than the average surface of the comet at visible wavelengths and display a significantly bluer spectrum. They do not exhibit significant changes over a period of a few weeks. All these observations are consistent with exposure of water ice at the surface of boulders produced by dislocation of the weakly consolidated layers that cover large areas of the nucleus. Laboratory experiments show that under simulated comet surface conditions, analog samples acquire a vertical stratification with an uppermost porous mantle of refractory dust overlaying a layer of hard ice formed by recondensation or sintering under the insulating dust mantle. The evolution of the visible spectrophotometric properties of samples during sublimation is consistent with the contrasts of brightness and color seen at the surface of the nucleus. Clustered bright spots are formed by the collapse of overhangs that is triggered by mass wasting of deeper layers. Isolated spots might be the result of the emission of boulders at low velocity that are redepositioned in other regions.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
10 Strategic Research Centers > Center for Space and Habitability (CSH)

UniBE Contributor:

Pommerol, Antoine; Thomas, Nicolas; Elmaarry, Mohamed Ramy; Jost, Bernhard; Marschall, Raphael and Poch, Olivier

Subjects:

500 Science > 520 Astronomy
500 Science > 530 Physics

ISSN:

0004-6361

Publisher:

EDP Sciences

Language:

English

Submitter:

Katharina Weyeneth-Moser

Date Deposited:

22 Jun 2016 10:57

Last Modified:

26 Jun 2016 02:16

Publisher DOI:

10.1051/0004-6361/201525977

Web of Science ID:

000365072200039

BORIS DOI:

10.7892/boris.81696

URI:

https://boris.unibe.ch/id/eprint/81696

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