Gas flow in near surface comet like porous structures: Application to 67P/Churyumov-Gerasimenko

Christou, Chariton; Dadzie, S. Kokou; Thomas, N.; Marschall, Raphael; Hartogh, P.; Jordá, L.; Kührt, Ekkehard; Wright, I. P.; Rodrigo, R.

doi:10.1016/j.pss.2018.06.009

Cited by 14 publications

(12 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This additional complexity stands in the way of more sophisticated numerical solutions. We A20, page 5 of 14 A&A 655, A20 (2021) have ignored the influence of heating of gas through collision with a hotter dust mantle, such as Christou et al (2018), in the present model, considering that these additional effects probably only result in relatively small changes in the position of the sublimation front due to the exponential change in sublimation rate with temperature. However, we have set a test with larger surface temperatures as an approximation for such physical processes.…”

Section: Thermal Modelmentioning

confidence: 99%

The effect of thermal conductivity on the outgassing and local gas dynamics from cometary nuclei

Pinzón-Rodríguez

Marschall

Gerig

et al. 2021

A&A

View full text Add to dashboard Cite

Aims. The aim of this work is to investigate the parameters influencing the generation of the inner comae of a comet with a spherical nucleus and to model the gas activity distribution around its nuclei. Here, we investigate the influence of thermal conductivity combined with sub-surface H2O and CO2-ice sources on insolation-driven sublimation and the resulting gas flow field. In the process, we adopted some of the rotational and surface properties of the target of the Rosetta mission, comet 67P/Churyumov-Gerasimenko (67P/CG). Methods. We used a simplified model of heat transport through the surface layer to establish sublimation rates from a H2O- and CO2-ice sub-surface into a vacuum. We then applied the 3D Direct Simulation Monte Carlo method to model the coma as a sublimation-driven flow. The free parameters of the model were used to test the range of effects arising from thermal inertia and the depth of the source on the gas outflow. Results. Thermal inertia and the depth of the sublimation front can have a strong effect on the emission distribution of the flow at the surface. In models with a thermal inertia up to 80 TIU (thermal inertia units: J m−2 K−1 s−1∕2), the H2O distribution can be rotated about the rotation axis by about 20° relative to models with no thermal lag. For CO2, the maximum activity can be shifted towards the sunset terminator with activity going far into the nightside for cases with low thermal diffusivity. The presence of a small amount of CO2 can reduce the presence of H2O by at least an order of magnitude on the nightside by blocking H2O flow. In addition, CO2 can also decrease the speed of the mixed flow in the same region up to 200 m s−1, compared to cases with no CO2 activity. Conclusions. Even low values of the thermal inertia can substantially modify the gas flow field. Including CO2 leads to strong variations in the local CO2/H2O density ratio between the dayside and nightside. CO2 can dominate the gas composition above the nightside and can also act to modify the H2O flow field close to the terminator.

show abstract

Section: Thermal Modelmentioning

confidence: 99%

The effect of thermal conductivity on the outgassing and local gas dynamics from cometary nuclei

Pinzón-Rodríguez

Marschall

Gerig

et al. 2021

A&A

View full text Add to dashboard Cite

show abstract

“…It is now the state-of-the-art method to represent porous medium structure with a resolution of a few microns. Christou et al (2018) and have directly applied the Direct Simulation Monte Carlo (DSMC) method to the computational mesh obtained from micro-CT images of highly porous rock samples. The flow of sublimating water ice from beneath the sample through the porous layer was studied.…”

Section: The Dust and Ice Boundary Layermentioning

confidence: 99%

“…Christou et al. ( 2018 ) and Christou et al. ( 2019 ) have directly applied the Direct Simulation Monte Carlo (DSMC) method to the computational mesh obtained from micro-CT images of highly porous rock samples.…”

Section: The Physics Of Developing Cometary Comaementioning

confidence: 99%

“…Figure adapted from Christou et al. ( 2018 )

Fig. 2 Gas pressure as function of porosity at 1 mm and 1 cm above the surface for two rock temperatures, , 330 K. Figure adapted from Christou et al.…”

Section: The Physics Of Developing Cometary Comaementioning

confidence: 99%

“…Gas temperature as function of porosity, , at 1 mm and 1 cm above the surface for two rock temperatures, T rock = 300 K, 330 K. The graphs were obtained by a polynomial interpolation from six different rock samples.Figure adaptedfromChristou et al (2018) …”

mentioning

confidence: 99%

See 2 more Smart Citations

Cometary Comae-Surface Links

et al. 2020

Self Cite

View full text Add to dashboard Cite

A comet is a highly dynamic object, undergoing a permanent state of change. These changes have to be carefully classified and considered according to their intrinsic temporal and spatial scales. The Rosetta mission has, through its contiguous in-situ and remote sensing coverage of comet 67P/Churyumov-Gerasimenko (hereafter 67P) over the time span of August 2014 to September 2016, monitored the emergence, culmination, and winding down of the gas and dust comae. This provided an unprecedented data set and has spurred a large effort to connect in-situ and remote sensing measurements to the surface. In this review, we address our current understanding of cometary activity and the challenges involved when linking comae data to the surface. We give the current state of research by describing what we know about the physical processes involved from the surface to a few tens of kilometres above it with respect to the gas and dust emission from cometary nuclei. Further, we describe how complex multidimensional cometary gas and dust models have developed from the Halley encounter of 1986 to today. This includes the study of inhomogeneous outgassing and determination of the gas and dust production rates. Additionally, the different approaches used and results obtained to link coma data to the surface will be discussed. We discuss forward and inversion models and we describe the limitations of the respective approaches. The current literature suggests that there does not seem to be a single uniform process behind cometary activity. Rather, activity seems to be the consequence of a variety of erosion processes, including the sublimation of both water ice and more volatile material, but possibly also more exotic processes such as fracture and cliff erosion under thermal and mechanical stress, sub-surface heat storage, and a complex interplay of these processes. Seasons and the nucleus shape are key factors for the distribution and temporal evolution of activity and imply that the heliocentric evolution of activity can be highly individual for every comet, and generalisations can be misleading.

show abstract

Gas Emissions Near the Nucleus

Thomas

2020

Astronomy and Astrophysics Library

View full text Add to dashboard Cite

Gas flow in near surface comet like porous structures: Application to 67P/Churyumov-Gerasimenko

Cited by 14 publications

References 40 publications

The effect of thermal conductivity on the outgassing and local gas dynamics from cometary nuclei

The effect of thermal conductivity on the outgassing and local gas dynamics from cometary nuclei

Cometary Comae-Surface Links

Gas Emissions Near the Nucleus

Contact Info

Product

Resources

About