Le pied diabétique

Fougere, Édouard

doi:10.1016/j.actpha.2019.05.030

Cited by 4 publications

(7 citation statements)

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“…It is plausible that the expansive dust deposits over the northern hemi-nucleus of 67P, formed by the deposition of ejecta from the south, contained a few per cent of water ice in mass (Hu et al 2017). Fougere et al (2016b). The estimates of water production based on DSMC (Direct Simulation Monte Carlo) are included (Fougere et al 2016a).…”

Section: Evolution Of Water Production Rate Of 67pmentioning

confidence: 99%

“…The first two rows of figure legend read 'mantle thickness -icy fraction area'. The reader is referred to Fougere et al (2016b), where the description of the measurement data and sources thereof are provided.…”

Section: Evolution Of Water Production Rate Of 67pmentioning

confidence: 99%

“…Figure 12.Total water production of 67P as function of time since perihelion in 2015, or heliocentric distance, estimated with the dust mantle thermal model for different mantle thickness and icy area fractions. The results are plotted in comparison with various measurements as presented inFougere et al (2016b). The estimates of water production based on DSMC (Direct Simulation Monte Carlo) are included(Fougere et al 2016a).…”

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confidence: 99%

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Thermal modelling of water activity on comet 67P/Churyumov-Gerasimenko with global dust mantle and plural dust-to-ice ratio

Shi

Sierks

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We perform a thermo-physical analysis on water activity of comet 67P/Churyumov-Gerasimenko (67P). The sublimation of water is assumed to occur from beneath a global, desiccated dust mantle over the irregular-shaped nucleus. The concept of two thermal models, the recipe of model formulation and the strategy of application to comet 67P are described. For an accurate and efficient evaluation of energy input by insolation and self-heating over the nucleus, a Landscape data base is devised based on polyhedral shape models of the nucleus. We apply the thermal models to investigate the impact of certain parameters of nucleus properties on water production. It is found that the measured water production of 67P can be overall attributed to sublimation of water ice with a mass abundance of a few to 10 per cent beneath a uniform dust mantle of several millimetres to one centimetre in thickness. Insofar as 67P is concerned, we argue against the necessity to invoke assumptions on localized water activity, or on the distinction of active/dormant surface areas.

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Section: Evolution Of Water Production Rate Of 67pmentioning

confidence: 99%

Section: Evolution Of Water Production Rate Of 67pmentioning

confidence: 99%

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confidence: 99%

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Thermal modelling of water activity on comet 67P/Churyumov-Gerasimenko with global dust mantle and plural dust-to-ice ratio

Shi

Sierks

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Our simple thermal model assumes the same thickness of the desiccated layer for the Northern and Southern hemisphere. Due to higher erosion rates in the South, this is likely not the case, and a shallower desiccated layer, or a larger area fraction of ice (Fougere et al 2016b), would explain our observations. A more thorough investigation in the near future demands application of more sophisticated thermo-physical models to treat not only non-uniform properties of the nucleus subsurface but also activity of multiple volatile species.…”

Section: Discussionmentioning

confidence: 70%

“…While the broad picture of the Whipple model, i.e., ices in the nucleus sublimate when heated by the Sun and the resulting gas outflow lifts dust (Whipple 1950), has been confirmed by observations, details of the processes involved remain the subject of debate. Observations of dust 'jets' have been traced to certain areas of the surface , and various models have been developed to trace gas and dust flow in the inner coma of 67P, with varying degrees of complexity (e.g., Fougere et al 2016a;Kramer & Noack 2016;Kramer et al 2017;Zakharov et al 2018), but these do not yet uniquely identify the surface features responsible for activity. Indeed, many of the models show that the bulk activity can be explained by moreor-less homogeneous activity from all illuminated surface facets (Keller et al 2015), and that jets in the inner coma are controlled more by the complex shape of the nucleus than by anything special about their apparent source on the surface (Shi et al 2018a).…”

Section: Introductionmentioning

confidence: 99%

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

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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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Modelling the water and carbon dioxide production rates of Comet 67P/Churyumov–Gerasimenko

Davidsson

Samarasinha

Farnocchia

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The European Space Agency Rosetta/Philae mission to Comet 67P/Churyumov–Gerasimenko in 2014–2016 is the most complete and diverse investigation of a comet carried out thus far. Yet, many physical and chemical properties of the comet remain uncertain or unknown, and cometary activity is still not a well-understood phenomenon. We here attempt to place constraints on the nucleus abundances and sublimation front depths of H2O and CO2 ice, and to reconstruct how the nucleus evolved throughout the perihelion passage. We employ the thermophysical modelling code ‘Numerical Icy Minor Body evolUtion Simulator’, or nimbus, to search for conditions under which the observed H2O and CO2 production rates are simultaneously reproduced before and after perihelion. We find that the refractories to water–ice mass ratio of relatively pristine nucleus material is μ ≈ 1, that airfall material has μ ≈ 2, and that the molar abundance of CO2 relative H2O is near 30 per cent. The dust mantle thickness is typically $\lesssim 2\, \mathrm{cm}$. The average CO2 sublimation front depths near aphelion were $\sim 3.8\, \mathrm{m}$ and $\sim 1.9\, \mathrm{m}$ on the northern and southern hemispheres, respectively, but varied substantially with time. We propose that airfall material is subjected to substantial fragmentation and pulverization due to thermal fatigue during the aphelion passage. Sub-surface compaction of material due to CO2 activity near perihelion seems to have reduced the diffusivity in a measurable way.

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Le pied diabétique

Cited by 4 publications

References 0 publications

Thermal modelling of water activity on comet 67P/Churyumov-Gerasimenko with global dust mantle and plural dust-to-ice ratio

Thermal modelling of water activity on comet 67P/Churyumov-Gerasimenko with global dust mantle and plural dust-to-ice ratio

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

Modelling the water and carbon dioxide production rates of Comet 67P/Churyumov–Gerasimenko

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