Comparison between the findings of Deep Impact and our experimental results on large samples of gas-laden amorphous ice

Bar‐Nun, A.; Pat-El, I.; Laufer, D.

doi:10.1016/j.icarus.2006.06.019

Cited by 4 publications

(3 citation statements)

References 22 publications

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“…Hornung et al (2016) recently reported the collection of cometary dust particles at low-impact velocities using the COSIMA instrument on the ROSETTA spacecraft, from which they deduced the pressure required for fragmentation (i.e., the tensile strength) to be between~0.8 and 14 kPa. Other modeling and observational studies of cometary material tensile strengths on the 10-100 μm scale are in agreement with these values (Bar-Nun et al, 2007;Biele et al, 2009).…”

Section: Meteoroid Fragmentationsupporting

confidence: 82%

Meteoric Smoke Deposition in the Polar Regions: A Comparison of Measurements With Global Atmospheric Models

et al. 2017

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The accumulation rate of meteoric smoke particles (MSPs) in ice cores—determined from the trace elements Ir and Pt, and superparamagnetic Fe particles—is significantly higher than expected from the measured vertical fluxes of Na and Fe atoms in the upper mesosphere and the surface deposition of cosmic spherules. The Whole Atmosphere Community Climate Model with the Community Aerosol and Radiation Model for Atmospheres has been used to simulate MSP production, transport, and deposition, using a global MSP input of 7.9 t d−1 based on these other measurements. The modeled MSP deposition rates are smaller than the measurements by factors of ~32 in Greenland and ~12 in Antarctica, even after reanalysis of the Ir/Pt ice core data with inclusion of a volcanic source. Variations of the model deposition scheme and use of the United Kingdom Chemistry and Aerosols model do not improve the agreement. Direct removal of MSP‐nucleated polar stratospheric cloud particles to the surface gives much better agreement, but would result in an unfeasibly high rate of nitrate deposition. The unablated fraction of cosmic dust (~35 t d−1) would provide sufficient Ir and Pt to account for the Antarctic measurements, but the relatively small flux of these large (>3 μm) particles would lead to greater variability in the ice core measurements than is observed, although this would be partly offset if significant fragmentation of cosmic dust particles occurred during atmospheric entry. Future directions to resolve these discrepancies between models and measurements are also discussed.

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Section: Meteoroid Fragmentationsupporting

confidence: 82%

Meteoric Smoke Deposition in the Polar Regions: A Comparison of Measurements With Global Atmospheric Models

et al. 2017

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“…, where Ȳ is the effective yield strengths of the target material. We adopt a value of Ȳ ≈ 10P a, as determined for comet Temple 1 and also in agreement with laboratory experiments (Richardson et al 2007, Bar-Nun et al 2007. Under the assumptions used previously, the depth of this crater for an impactor of size 10µm is 600µm, i.e., roughly the penetration depth of the solar protons.…”

Section: Timescale Of Collisional Re-surfacingmentioning

confidence: 61%

Collisions, cosmic radiation and the colors of the Trojan asteroids

Melita¹,

Strazzulla²,

Bar‐Nun³

2009

Icarus

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a b s t r a c tThe Trojan asteroids orbit about the Lagrangian points of Jupiter and the residence times about their present location are very long for most of them. If these bodies originated in the outer Solar System, they should be mainly composed of water ice, but, in contrast with comets, all the volatiles close to the surface would have been lost long ago. Irrespective of the rotation period, and hence the surface temperature and ice sublimation rate, a dust layer exists always on the surface. We show that the timescale for resurfacing the entire surface of the Trojan asteroids is similar to that of the flattening of the red spectrum of the new dust by solar-proton irradiation. This, if the cut-off radius of the size distribution of the impacting objects is between 1 mm and 1 m and its slope is À3, for the entire size range. Therefore, the surfaces of most Trojan asteroids should be composed mainly of unirradiated dust.

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“…From laboratory experiments, it is possible to measure the strengths of cometary material analogs, with the strong limitation that we do not know well the nature of the cometary material, therefore the ground truth of the studied analogs. Various analogs made of water ice grains and/or dust grains have been studied, with an estimated tensile strength in the range 2 -4 kPa for pure 200 micron size water ice grains (Bar-Nun et al 2007) and in the range 1 -10 kPa for micrometre size siliceous grains (Blum et al 2006). The compressive strength has also been estimated to 0.3 -1 MPa by Jessberger and Kotthaus (1989) for micron size low density aggregates of water ice and dust grains.…”

Section: State Of the Art Before Rosettamentioning

confidence: 99%

The Thermal, Mechanical, Structural, and Dielectric Properties of Cometary Nuclei After Rosetta

et al. 2019

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The physical properties of cometary nuclei observed today relate to their complex history and help to constrain their formation and evolution. In this article, we review some of the main physical properties of cometary nuclei and focus in particular on the thermal, mechanical, structural and dielectric properties, emphasizing the progress made during the Rosetta mission. Comets have a low density of 480 ± 220 kg m -3 and a low permittivity of 1.9 -2.0, consistent with a high porosity of 70 -80 %, are weak with a very low global tensile strength <100 Pa, and have a low bulk thermal inertia of 0 -60 J K -1 m -2 s -1/2 that allowed them to preserve highly volatiles species (e.g. CO, CO2, CH4, N2) into their interior since their formation. As revealed by 67P/Churyumov-Gerasimenko, the above physical properties vary across the nucleus, spatially at its surface but also with depth. The broad picture is that the bulk of the nucleus consists of a weakly bonded, rather homogeneous material that preserved primordial properties under a thin shell of processed material, and possibly covered by a granular material; this cover might in places reach a thickness of several meters. The properties of the top layer (the first meter) are not representative of that of the bulk nucleus. More globally, strong nucleus heterogeneities at a scale of a few meters are ruled out on 67P's small lobe.

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Comparison between the findings of Deep Impact and our experimental results on large samples of gas-laden amorphous ice

Cited by 4 publications

References 22 publications

Meteoric Smoke Deposition in the Polar Regions: A Comparison of Measurements With Global Atmospheric Models

Meteoric Smoke Deposition in the Polar Regions: A Comparison of Measurements With Global Atmospheric Models

Collisions, cosmic radiation and the colors of the Trojan asteroids

The Thermal, Mechanical, Structural, and Dielectric Properties of Cometary Nuclei After Rosetta

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