Knowledge of the surface temperature distribution on a comet’s nucleus and its temporal evolution at different timescales is key to constraining its thermophysical properties and understanding the physical processes that take place at and below the surface. Here we report on time-resolved maps of comet 67P/Churyumov–Gerasimenko retrieved on the basis of infrared data acquired by the Visible InfraRed and Thermal Imaging Spectrometer (VIRTIS) onboard the Rosetta orbiter in 2014, over a roughly two-month period in the pre-perihelion phase at heliocentric distances between 3.62 and 3.31 au from the Sun. We find that at a spatial resolution ≤15 m per pixel, the measured temperatures point out the major effect that self-heating, due to the complex shape of the nucleus, has on the diurnal temperature variation. The bilobate nucleus of comet 67P also induces daytime shadowing effects, which result in large thermal gradients. Over longer periods, VIRTIS-derived temperature values reveal seasonal changes driven by decreasing heliocentric distance combined with an increasing abundance of ice within the uppermost centimetre-thick layer, which implies the possibility of having a largely pristine nucleus interior already in the shallow subsurface.
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The VIRTIS calibrated data are publicly available through the ESA’s Planetary Science Archive (PSA) website (https://archives.esac.esa.int/psa/) and NASA’s Planetary Data System (https://pds.nasa.gov/) in accordance with the schedule established by the Rosetta project. Other data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request. Readers are welcome to comment on the online version of the paper.
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The authors thank the following institutions and agencies, which supported this work: Italian Space Agency (ASI-Italy), Centre National d’Etudes Spatiales (CNES-France), Deutsches Zentrum für Luft- und Raumfahrt (DLR-Germany), National Aeronautic and Space Administration (NASA-USA). VIRTIS was built by a consortium from Italy, France and Germany, under the scientific responsibility of IAPS, Istituto di Astrofisica e Planetologia Spaziali of INAF, Rome, Italy, which led also the scientific operations. The VIRTIS instrument development for ESA has been funded and managed by ASI, with contributions from Observatoire de Meudon financed by CNES and from DLR. The VIRTIS instrument industrial prime contractor was former Officine Galileo, now Leonardo SpA in Campi Bisenzio, Florence, Italy. The authors thank the Rosetta Liaison Scientists, the Rosetta Science Ground Segment and the Rosetta Mission Operations Centre for their support in planning the VIRTIS observations. We also thank the MIRO science and MIRO archiving teams for making MIRO data available to us before their public release. This research has made use of NASA’s Astrophysics Data System. D.K. acknowledges DFG-grant KA 3757/2-1. This work is dedicated to Angioletta Coradini (1946–2011), conceiver of the VIRTIS instrument, and to Sergio Fonti (1945–2018), co-author of this Article and active contributor in the development of VIRTIS. The first author dedicates this work also to Luca Malagutti (1965–2017), who was a brilliant researcher at the University of Milan.
The authors declare no competing interests.
Journal peer review information: Nature Astronomy thanks Ben Rozitis and the other anonymous reviewer(s) for their contribution to the peer review of this work.
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Tosi, F., Capaccioni, F., Capria, M.T. et al. The changing temperature of the nucleus of comet 67P induced by morphological and seasonal effects. Nat Astron 3, 649–658 (2019). https://doi.org/10.1038/s41550-019-0740-0
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Space Science Reviews (2020)
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