Properties of the 67P/Churyumov-Gerasimenko interior revealed by CONSERT radar

Kofman, W.; Hérique, Alain; Barbin, Yves; Barriot, J. P.; Ciarletti, Valérie; Clifford, Stephen M.; Edenhofer, P.; Elachi, C.; Eyraud, Christelle; Goutail, J. P.; Heggy, E.; Jordá, L.; Lasue, J.; Levasseur-Regourd, Anny Chantal; Nielsen, E.; Pasquero, Pierre; Preusker, Frank; Puget, P.; Plettemeier, Dirk; Rogez, Yves; Sierks, H.; Statz, Christoph; Svedhem, H.; Williams, I. P.; Zine, Sonia; Zyl, Jakob van

doi:10.1126/science.aab0639

Cited by 208 publications

(216 citation statements)

References 39 publications

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“…It therefore seems reasonably safe to conclude that in the hypothesis of a homogeneous nucleus, the dielectric constant value would be lower than 1.35, consistent with a 80% porosity and a dust-to-ice ratio lower than 1.5 (Brouet et al 2015). This value is consistent with the average value of about 1.27 that has been estimated by Kofman et al (2015) after a study performed on a homogeneous nucleus and based on the propagation delays measured by CONSERT.…”

Section: Qualitative Comparison With Consert Data and Discussionsupporting

confidence: 78%

“…Even if the orbit configuration resulting from the final landing site location did not allow us to perform any measurement in visibility that could have been used as reference, the measurements that were performed show that signal was clearly received (Kofman et al 2015) throughout both FSS-W and FSS-E. Given the geometrical configurations during these two sequences of the FSS, only the sounding of the smaller lobe of the cometary nucleus was possible then.…”

Section: Qualitative Comparison With Consert Data and Discussionmentioning

confidence: 99%

“…Even if the Philae location is still not known with accuracy, triangulation performed with the delays measured with CONSERT have allowed narrowing down the uncertainty on its location (Kofman et al 2015) to 20 m × 200 m. The work presented here assumes that Philae is located at the current best estimate of the actual Philae location at Abydos that is shown in Fig. 1 with a black dot on the 3D shape model of the nucleus.…”

Section: D Nucleus Shape and Geometrical Configurationmentioning

confidence: 99%

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CONSERT suggests a change in local properties of 67P/Churyumov-Gerasimenko’s nucleus at depth

Ciarletti

Levasseur-Regourd

Lasue

et al. 2015

A&A

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Context. After the successful landing of Philae on the nucleus of 67P/Churyumov-Gerasimenko, the Rosetta mission provided the first opportunity of performing measurements with the CONSERT tomographic radar in November 2014. CONSERT data were acquired during this first science sequence. They unambiguously showed that propagation through the smaller lobe of the nucleus was achieved. Aims. While the ultimate objective of the CONSERT radar is to perform the tomography of the nucleus, this paper focuses on the local characterization of the shallow subsurface in the area of Philae's final landing site, specifically determining the possible presence of a permittivity gradient below the nucleus surface. Methods. A number of electromagnetic simulations were made with a ray-tracing code to parametrically study how the gradient of the dielectric constant in the near-subsurface affects the ability of CONSERT to receive signals. Results. At the 90 MHz frequency of CONSERT, the dielectric constant is a function of porosity, composition, and temperature. The dielectric constant values considered for the study are based on observations made by the other instruments of the Rosetta mission, which indicate a possible near-surface gradient in physical properties and on laboratory measurements made on analog samples. Conclusions. The obtained simulated data clearly show that if the dielectric constant were increasing with depth, it would have prevented the reception of signal at the CONSERT location during the first science sequence. We conclude from our simulations that the dielectric constant most probably decreases with depth.

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Section: Qualitative Comparison With Consert Data and Discussionsupporting

confidence: 78%

Section: Qualitative Comparison With Consert Data and Discussionmentioning

confidence: 99%

Section: D Nucleus Shape and Geometrical Configurationmentioning

confidence: 99%

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CONSERT suggests a change in local properties of 67P/Churyumov-Gerasimenko’s nucleus at depth

Ciarletti

Levasseur-Regourd

Lasue

et al. 2015

A&A

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“…Therefore, to release one kilogram of carbon monoxide, a cavity with a volume greater than 1000 m 3 is required. The size of such a cavity is close to the limiting evaluation of interior heterogeneities obtained by CONSERT (Kofman et al 2015). Second, the cavity scenario requires that the gas should remain in the pre-existing cavity for a long time, i.e., a time at least comparable to the typical lifetime of comets in the inner solar system.…”

Section: Subsurface Geysermentioning

confidence: 90%

A model of short-lived outbursts on the 67P from fractured terrains

Skorov

Rezac

Hartogh

et al. 2016

A&A

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Aims. We develop a physical model to explain the potent outbursts that occurred in the fractured terrain of comet 67P near perihelion, and predict its temporal characteristics. Methods. The feasibility of the proposed mechanism is studied using a numerical model accounting for the relevant microscopic/macroscopic processes. We rely on the thermophysical, compositional, and geo-morphological data from the published measurements of respective instruments on board Rosetta. Results. The key idea of this novel mechanism is built around observations of fractures/cracks in the region of interest. It is argued that as the stresses on the nucleus increased during the perihelion approach, a crack deepening event occurred reaching the deeper material containing super-volatile ices in equilibrium with the surrounding. This sudden opening lead to a violent sublimation of the super-volatile ices. The time scales and mass release of this process are modeled and reported. In our modeling we pay attention to the question of the existence of super-volatile ices in the deeper interior for a long time, and the thermal equilibrium in the interior. Conclusions. The deepening of pre-existing cracks (fracture) into the material containing highly volatile ices can explain the observed outburst features. The sudden disequilibration of the steady-state reservoir of highly volatile ices results in a violent release of gas and dust. The proposed mechanism also explains the rapid shut down of this activity in accordance with the observations. The proposed mechanism is independent of solar illumination history of a given region, or the pre-existance of large sealed nucleus cavities.

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“…Electromagnetic waves are absorbed in a dielectric medium, such as rocks and ices, and can be scat-tered by cracks, voids and other irregularities at scales comparable to the wavelength. However, assuming the results of the CONSERT experiment on board Rosetta can be used to predict the expected bulk dielectric properties of MBCs, then both dielectric attenuation and volume scattering should be low (Kofman et al 2015).…”

Section: In Situ Detection Of Watermentioning

confidence: 99%

The Main Belt Comets and ice in the Solar System

Snodgrass

Agarwal

Combi

et al. 2017

Astron Astrophys Rev

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We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies.

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Properties of the 67P/Churyumov-Gerasimenko interior revealed by CONSERT radar

Cited by 208 publications

References 39 publications

CONSERT suggests a change in local properties of 67P/Churyumov-Gerasimenko’s nucleus at depth

CONSERT suggests a change in local properties of 67P/Churyumov-Gerasimenko’s nucleus at depth

A model of short-lived outbursts on the 67P from fractured terrains

The Main Belt Comets and ice in the Solar System

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