Publication Date:
2015-09-25
Description:
Observations of cometary nuclei have revealed a very limited amount of surface water ice, which is insufficient to explain the observed water outgassing. This was clearly demonstrated on comet 9P/Tempel 1, where the dust jets (driven by volatiles) were only partially correlated with the exposed ice regions. The observations of 67P/Churyumov-Gerasimenko have revealed that activity has a diurnal variation in intensity arising from changing insolation conditions. It was previously concluded that water vapour was generated in ice-rich subsurface layers with a transport mechanism linked to solar illumination, but that has not hitherto been observed. Periodic condensations of water vapour very close to, or on, the surface were suggested to explain short-lived outbursts seen near sunrise on comet 9P/Tempel 1. Here we report observations of water ice on the surface of comet 67P/Churyumov-Gerasimenko, appearing and disappearing in a cyclic pattern that follows local illumination conditions, providing a source of localized activity. This water cycle appears to be an important process in the evolution of the comet, leading to cyclical modification of the relative abundance of water ice on its surface.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉De Sanctis, M C -- Capaccioni, F -- Ciarniello, M -- Filacchione, G -- Formisano, M -- Mottola, S -- Raponi, A -- Tosi, F -- Bockelee-Morvan, D -- Erard, S -- Leyrat, C -- Schmitt, B -- Ammannito, E -- Arnold, G -- Barucci, M A -- Combi, M -- Capria, M T -- Cerroni, P -- Ip, W-H -- Kuehrt, E -- McCord, T B -- Palomba, E -- Beck, P -- Quirico, E -- VIRTIS Team -- England -- Nature. 2015 Sep 24;525(7570):500-3. doi: 10.1038/nature14869.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto di Astrofisica e Planetologia Spaziali - INAF, via del fosso del cavaliere 100, 00133 Rome, Italy. ; Institute for Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany. ; LESIA-Observatoire de Paris, CNRS, Universite Pierre et Marie Curie, Universite Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France. ; Universite Grenoble Alpes - CNRS Institut de Planetologie et Astrophysique de Grenoble, Batiment D de Physique, BP 53, 38041 Grenoble Cedex 9, France. ; University of California, Los Angeles, California 90095, USA. ; Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward Street, Ann Arbor, Michigan 48109, USA. ; National Central University, No. 300, Jhongda Road, Jhongli District, Taoyuan City, 32001 Taipei, Taiwan. ; Bear Fight Institute, 22 Fiddler's Road, Box 667, Winthrop, Washington 98862, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26399830" target="_blank"〉PubMed〈/a〉
Keywords:
Extraterrestrial Environment/*chemistry
;
Ice/*analysis
;
*Meteoroids
;
Temperature
;
Time Factors
;
Volatilization
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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