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Old 24th October 2018, 05:13 PM   #14
Sol88's Avatar
Join Date: Mar 2009
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Not actual rock, jd116.

It's just the word astronomers use to describe the mixture of MOSTLY dust with SOME ice's.


at 80 odd percent the comet nucleus is actually MOSTLY empty voids.

So, for want of a better word and thanks to Reality Check we can now use the word ROCK.

but we understand not actual ROCK but some majical mixture of NOTHING, DUST with some ice.

From the operation of the MUPUS thermal probe Spohn et al. (2015) concluded that the material of the nucleus of 67P/Churyumov–Gerasimenko is likely to have a high strength, at least locally at the Philae landing site. In this work we consider the derived strength of the material in order to constrain its granulation. For this purpose we performed numerical simulations of the long–term sintering of ice–dust granular mixtures of different granulation, covered by a dust mantle. The dust mantle has a thickness of 0 – 16 cm, and a (pore size and temperature–dependent) thermal conductivity. According to our simulations a hardened layer at least a meter thick forms beneath the dust only when the grains are tens of microns in radius, or smaller.
In order to better simulate the topography at the Philae landing site, we simulated the evolution of the material when the solar flux is reduced by
25%. In both cases, also when the illumination was deliberately overestimated, our simulations indicate that the coarse–grained material should not undergo significant sintering. However, the failed attempt to penetrate the subsurface later by MUPUS-PEN probably indicates high strength
Comet 67P/Churyumov-Gerasimenko:
hardening of the sub-surface layer

(c) What are comets made of?
At the simplest level, a very basic question is whether comets are mostly ice or mostly rock/dirt/refractory material. Whipple’s [2] model of the dirty snowball, the first quantitative model, envisioned cometary nuclei as mostly ice, although our understanding has been evolving more toward mostly rock, particularly for 67P/C-G for which refractory/volatile ratios as high as 6 have been cited [3,4]. Nevertheless, there is still considerable uncertainty about even this basic parameter, not least of which is that most measurements are subject to selection effects in removing refractories from the nucleus to the coma, where they are observed as dust.
Comets: looking ahead Michael F. A’Hearn

The mechanical properties of the surface in a number of different regions were constrained by comparing gravitational slopes and surface morphology [47],
where low slope (0-20°) terrains contained mainly fine material and few large isolated boulders (> 10 m), intermediate slope terrains (20°-45°) associated with fallen consolidated material, debris fields with numerous
intermediate size boulders (< 1m – 10m) and high-slope terrain (45-90°) being cliff regions with exposed consolidated material with no boulders or fine material. Here consolidated is used to refer to areas that appear
rocky in appearance and are cohesive enough to display lineaments and fractures.
The Rosetta mission orbiter Science overview – the comet phase M.G.G.T. Taylor (1), N. Altobelli (2), B. J. Buratti (3) and M. Choukroun

but not actual rock.
“No rock. Any charge separation is limited. The electric field is pointing in the wrong direction. Currents are doing nothing.” Jonesdave116.

“The 'electric comet' is physically IMPOSSIBLE to model using mainstream science! PERIOD! True story! End of story!” Indagator

Last edited by Sol88; 24th October 2018 at 05:26 PM.
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