3D thermal modeling of two selected regions on comet 67P and comparison with Rosetta/MIRO measurements

Macher, W.; Kömle, Norbert I.; Skorov, Yu. V.; Rezac, Ladislav; Kargl, Günter; Tiefenbacher, Patrick

doi:10.1051/0004-6361/201834798

Cited by 11 publications

(7 citation statements)

References 20 publications

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“…For instance, Keller et al (2015) showed that self-heating could reach 50% of the total energy received in some areas of the neck region. Macher et al (2019) also showed that, even though the average contribution of self-heating in the regions they studied was evaluated to be 1% of the direct insolation, it can be enhanced in rough areas not reached by direct insolation. In these locations, it could reach as much as 50% of the direct insolation contribution.…”

Section: Local and Global Shape Effectsmentioning

confidence: 89%

“…Each facet gets its own boundary condition at the surface. Therefore, a 1D thermal evolution model is the best option, further justified by the results of Macher et al (2019), who found that temperature differences at the surface of 67P between a 1D and a 3D thermal simulation (i.e., accounting for lateral heat fluxes) amount to only ∼ 0.1%.…”

Section: Main Equationsmentioning

confidence: 97%

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Evolution of pits at the surface of 67P/Churyumov-Gerasimenko

Benseguane

Guilbert-Lepoutre

Lasue

et al. 2022

A&A

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Context. The observation of pits at the surface of comets offers the opportunity to take a glimpse into the properties and the mechanisms that shape a nucleus through cometary activity. If the origin of these pits is still a matter of debate, multiple studies have recently suggested that known phase transitions (such as volatile sublimation or amorphous water ice crystallization) alone could not have carved these morphological features on the surface of 67P/Churyumov-Gerasimenko (hereafter 67P). Aims. We want to understand how the progressive modification of 67P's surface due to cometary activity might have affected the characteristics of pits and alcoves. In particular, we aim to understand whether signatures of the formation mechanism of these surface morphological features can still be identified. Methods. To quantify the amount of erosion sustained at the surface of 67P since it arrived on its currently observed orbit, we selected 380 facets of a medium-resolution shape model of the nucleus, sampling 30 pits and alcoves across the surface. We computed the surface energy balance with a high temporal resolution, including shadowing and self-heating contributions. We then applied a thermal evolution model to assess the amount of erosion sustained after ten orbital revolutions under current illumination conditions. Results. We find that the maximum erosion sustained after ten orbital revolutions is on the order of 80 m, for facets located in the southern hemisphere. We thus confirm that progressive erosion cannot form pits and alcoves, as local erosion is much lower than their observed depth and diameter. We find that plateaus tend to erode more than bottoms, especially for the deepest depressions, and that some differential erosion can affect their morphology. As a general rule, our results suggest that sharp morphological features tend to be erased by progressive erosion. Conclusions. This study supports the assumption that deep circular pits, such as Seth_01, are the least processed morphological features at the surface of 67P, or the best preserved since their formation.

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Section: Local and Global Shape Effectsmentioning

confidence: 89%

Section: Main Equationsmentioning

confidence: 97%

Evolution of pits at the surface of 67P/Churyumov-Gerasimenko

Benseguane

Guilbert-Lepoutre

Lasue

et al. 2022

A&A

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“…Third, the slow migration rate of scarp "h" may also point to stratigraphic differences in the volume of ice within the local subsurface. Specifically, scarps "d" and "a" may only be removing an entire seasonally processed layer of material (Figure 10), the thickness (L seasonal ) of which is simply the thermal skin depth, given by Macher et al (2019),…”

Section: Hypothesis and Interpretationsmentioning

confidence: 99%

Topographically Influenced Evolution of Large-scale Changes in Comet 67P/Churyumov–Gerasimenko's Imhotep Region

et al. 2022

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Large portions of comet 67P/Churyumov–Gerasimenko’s northern hemisphere are blanketed by fallback material consisting of centimeter-sized particles termed the smooth terrains. Observations from the Rosetta mission show that the most drastic transient changes during 67P’s 2015 perihelion passage occurred within a subset of these deposits. However, we still do not understand the processes driving these changes, limiting our overall understanding of how comets evolve over both seasonal and multiorbit timescales. Herein we provide a complete documentation of scarp-driven activity on 67P’s largest smooth terrain deposit, a highly active portion of the Imhotep region that is the southernmost of all smooth terrain basins on 67P. We also present a thermal model that accurately predicts when and where scarps originate during the course of the observed activity. Assuming a uniform surface composition, our model shows that activity is heavily controlled by local topography rather than the presence of ice-enhanced hot spots on the surface. Scarps within the smooth terrain deposits in central Imhotep also exhibit a peculiar behavior, where three scarps originate from the same location but at different times and migrate in opposite directions. This behavior indicates that the landscape retains a memory of previous cycles of erosion and deposition, reflected by the depth of the volatile-rich layer. Future work will need to couple our thermal model with a landscape evolution model in order to explain the complete dynamic evolution of these terrains.

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“…We are particularly interested in the flat areas as this allows to use the least complex thermophysical model. Indeed, it was shown that surface roughness and the presence of shadows or cliffs, as well as self-heating effects need to be taken into account in non-flat regions (Macher et al 2019). By choosing particularly flat areas, we avoid these effects and increase the reliability of our results.…”

Section: Selection Of a Suitable Miro Data Setmentioning

confidence: 90%

“…In this work, we use the MIRO observations to derive the submm/mm optical properties of the near-surface material of comet 67P. In contrast to Schloerb et al (2015) and Macher et al (2019), who assumed an absorption coefficient for their calculations, we use a thermophysical model, which provides a temperature profile for the upper layers of the cometary nucleus. We then derive the complex index of refraction by fitting the temperature measurements of 67P's sub-surface made by MIRO with synthetic temperatures derived from the thermophysical and radiative-transfer model.…”

Section: Introductionmentioning

confidence: 99%

Sub-mm/mm optical properties of real protoplanetary matter derived from Rosetta/MIRO observations of comet 67P

Burger

Glißmann

Lethuillier

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Optical properties are required for the correct understanding and modelling of protoplanetary and debris discs. By assuming that comets are the most pristine bodies in the solar system, our goal is to derive optical constants of real protoplanetary material. We determine the complex index of refraction of the near-surface material of comet 67P/Churyumov-Gerasimenko by fitting the sub-millimetre/millimetre observations of the thermal emission of the comet’s sub-surface made by the Microwave Instrument for the Rosetta Orbiter (MIRO) with synthetic temperatures derived from a thermophysical model and radiative-transfer models. According to the two major formation scenarios of comets, we model the sub-surface layers to consist of pebbles as well as of homogeneously packed dust grains. In the case of a homogeneous dusty surface material, we find a solution for the length-absorption coefficient of α ≈ 0.22 cm−1 for a wavelength of 1.594 mm and α ≥ 3.84 cm−1 for a wavelength of 0.533 mm and a constant thermal conductivity of 0.006 Wm−1K−1. For the pebble scenario, we find for the pebbles and a wavelength of 1.594 mm a complex refractive index of n = (1.074 − 1.256) + i (2.580 − 7.431) · 10−3 for pebble radii between 1 mm and 6 mm. Taking into account other constraints, our results point towards a pebble makeup of the cometary sub-surface with pebble radii between 3 mm and 6 mm. The derived real part of the refractive index is used to constrain the composition of the pebbles and their volume filling factor. The optical and physical properties are discussed in the context of protoplanetary and debris disc observations.

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3D thermal modeling of two selected regions on comet 67P and comparison with Rosetta/MIRO measurements

Cited by 11 publications

References 20 publications

Evolution of pits at the surface of 67P/Churyumov-Gerasimenko

Evolution of pits at the surface of 67P/Churyumov-Gerasimenko

Topographically Influenced Evolution of Large-scale Changes in Comet 67P/Churyumov–Gerasimenko's Imhotep Region

Sub-mm/mm optical properties of real protoplanetary matter derived from Rosetta/MIRO observations of comet 67P

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