The global meter-level shape model   of comet 67P/Churyumov-Gerasimenko

Preusker, Frank; Scholten, F.; Matz, Klaus-Dieter; Roatsch, Thomas; Hviid, S. F.; Mottola, S.; Knollenberg, J.; Kührt, Ekkehard; Pajola, M.; Oklay, N.; Vincent, Jean‐Baptiste; Davidsson, B.; A’Hearn, Michael F.; Agarwal, Jessica; Barbieri, C.; Barucci, M. A.; Bertaux, Jean-Loup; Bertini, Ivano; Cremonese, G.; Deppo, Vania Da; Debei, S.; Cecco, M. De; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Ip, W. H.; Jordá, L.; Keller, H. U.; Koschny, D.; Kramm, J.-R.; Küppers, M.; Lamy, Philippe; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez; Marzari, F.; Massironi, Matteo; Naletto, G.; Rickman, H.; Rodrigo, R.; Sierks, H.; Thomas, Nicolas; Tubiana, C.

doi:10.1051/0004-6361/201731798

Cited by 124 publications

(70 citation statements)

References 9 publications

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“…The effective spherical diameters, calculated from the best fit ellipsoidal dimensions in the second column, are presented in the third column and provide perhaps the best single number for the size of the object. The density for 67P is exceedingly well determined (16) and lies roughly in the middle of the ranges estimated for JFC nuclei. Due to the jetting force from cometary outgassing, the rotational periods of JFC nuclei change with time, so only approximate current values are listed for them.…”

Section: Supplementary Text Expected Impact Crater Morphologiesmentioning

confidence: 75%

“…Comets 19P, 67P, and 103P appear to be highly elongated bilobate objects, suggesting the merger of two distinct bodies, as has been proposed for Arrokoth (1,18), though for comets it is also possible that thermal evolution has generated this shape (e.g., 60). Except for 67P, whose bulk density is 538 ± 1 kg m -3 (16), the densities of the other JFC nuclei are uncertain by a factor of two or more, but all are consistent with ~500 kg m -3 (61), which implies average bulk porosities of ~50-80%. Arrokoth's density is likely greater than 290 kg m -3 (see above), and thus at least consistent with those of JFC nuclei.…”

Section: Comparison To Jupiter Family Cometsmentioning

confidence: 95%

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The geology and geophysics of Kuiper Belt object (486958) Arrokoth

Spencer¹,

Stern²,

Moore³

et al. 2020

Science

208

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The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, is composed of primitive objects preserving information about Solar System formation. In January 2019, the New Horizons spacecraft flew past one of these objects, the 36-kilometer-long contact binary (486958) Arrokoth (provisional designation 2014 MU69). Images from the flyby show that Arrokoth has no detectable rings, and no satellites (larger than 180 meters in diameter) within a radius of 8000 kilometers. Arrokoth has a lightly cratered, smooth surface with complex geological features, unlike those on previously visited Solar System bodies. The density of impact craters indicates the surface dates from the formation of the Solar System. The two lobes of the contact binary have closely aligned poles and equators, constraining their accretion mechanism.

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Section: Supplementary Text Expected Impact Crater Morphologiesmentioning

confidence: 75%

Section: Comparison To Jupiter Family Cometsmentioning

confidence: 95%

The geology and geophysics of Kuiper Belt object (486958) Arrokoth

Spencer¹,

Stern²,

Moore³

et al. 2020

Science

208

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“…9 (top panel), along with a map identifying the different regions of the nucleus (bottom panel). The distribution of solar irradiance is calculated on a polyhedral shape model representing the nucleus of 67P with 499,902 facets (Preusker et al 2017). For each epoch, the Sun's position in the Cheops body-fixed frame of the comet (as defined in Preusker et al 2015) is derived from the reconstructed ephemeris and rotational status of 67P using the SPICE tool-kit (Acton 1996).…”

Section: Discussionmentioning

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

A&A

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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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“…Possible outliers are the cold classical Borasisi and the 2:1 resonant body 2002 WC 19 ; those may have higher densities but uncertainties are huge. For comparison, precise measurement of the 67P/Churyumov Gerasimenko nucleus by the Rosetta mission yields a density of 537.8±0.7 kg/m 3 , and a large porosity (70-80%, Sierks et al 2015;Pätzold et al 2016;Preusker et al 2017). Vilenius et al (2014) also found that the sizes of the binaries components for objects smaller than 400 km are not significantly different from each other.…”

Section: Ring Thermal Emissionmentioning

confidence: 97%

Trans-Neptunian objects and Centaurs at thermal wavelengths

Müller

Lellouch

Fornasier

2020

The Trans-Neptunian Solar System

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The thermal emission of transneptunian objects (TNO) and Centaurs has been observed at mid-and far-infrared wavelengths -with the biggest contributions coming from the Spitzer and Herschel space observatories-, and the brightest ones also at sub-millimeter and millimeter wavelengths. These measurements allowed to determine the sizes and albedos for almost 180 objects, and densities for about 25 multiple systems. The derived very low thermal inertias show evidence for a decrease at large heliocentric distances and for high-albedo objects, which indicates porous and low-conductivity surfaces. The radio emissivity was found to be low ( r =0.70±0.13) with possible spectral variations in a few cases. The general increase of density with object size points to different formation locations or times. The mean albedos increase from about 5-6% (Centaurs, Scattered-Disk Objects) to 15% for the Detached objects, with distinct cumulative albedo distributions for hot and cold classicals. The color-albedo separation in our sample is evidence for a compositional discontinuity in the young Solar System. The median albedo of the sample (excluding dwarf planets and the Haumea family) is 0.08, the albedo of Haumea family members is close to 0.5, best explained by the presence of water ice. The existing thermal measurements remain a treasure trove at times where the far-infrared regime is observationally not accessible. Radiometric techniques 3.1 Models to interpret thermal measurementsRadiometry is a powerful technique to derive size, albedo, and thermal properties from thermal infrared measurements. The technique consists in the exploitation and interpretation of thermal data (see Section 2) in combination with data in the visible. The visible data are mainly obtained from the ground and include the object's absolute magnitude and estimates for the phase integral q. The most accurate radiometric properties are determined when objects are observed close to their thermal emission peaks, preferentially shortwards and longwards of the peak. For Centaurs and TNOs these peaks are located in the FIR regime between ≈50 and 100 µm (accessible from space only).There are different thermal models to obtain size and albedo of atmosphereless small bodies: simple models like the Standard Thermal Model (STM), the Fast Rotating Thermal Model (FRM), or the near-Earth asteroid thermal model (NEATM) or more complex thermophysical models (TPM) are used (see Delbo' et al. 2015 for a detailed discussion). For Centaurs and TNOs, mostly the NEATM are applied. In cases where the object is lacking shape or spin properties, the NEATM is often used. The beaming factor η is then either fitted to multi-band thermal measurements or a default value is applied. The STM/NEATM concepts can also handle elongated shapes (Brown 1985;Lellouch et al. 2017;Vilenius et al. 2018), but have severe limitations when thermal measurements cover different aspect angles 14 .In cases where the rotation period is known, the TPM concepts have the advantage that in addition to the stan...

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The global meter-level shape model of comet 67P/Churyumov-Gerasimenko

Cited by 124 publications

References 9 publications

The geology and geophysics of Kuiper Belt object (486958) Arrokoth

The geology and geophysics of Kuiper Belt object (486958) Arrokoth

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

Trans-Neptunian objects and Centaurs at thermal wavelengths

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