What was the cooling rate of cometary dust particles when they were collected by the Stardust spacecraft ?

Details What was the cooling rate of cometary dust particles when they were collected by the Stardust spacecraft ? What was the cooling rate of cometary dust particles when they were collected by the Stardust spacecraft ?

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmmr13c1395r&link_type=abstract

American Geophysical Union, Fall Meeting 2007, abstract #MR13C-1395

Other

3652 Pressure-Temperature-Time Paths, 5120 Plasticity, Diffusion, And Creep, 5134 Thermal Properties, 6022 Impact Phenomena (5420, 8136), 6023 Comets: Dust Tails And Trails (6210)

Scientific paper

Cometary dust particles are considered as relicts of pristine materials that accreted to form primitive meteorites and eventually planets. Compared to other small primitive objects of the solar system, cometary grains are poorly known. In this respect, the first sample return of cometary materials, the Stardust mission, raised considerable expectations from astrophysicists, geologists and cosmochemists. Indeed, these dusts are the only undisputable comet samples available so far. The mission was a plain success but still had to face inherent problems related to the collect of samples itself. The grains were captured from the 81P/Wild 2 comet tail at a relative velocity of 6.1 km/s in a low density silica aerogel medium. During this hypervelocity impact, flash heating of dusts could not be avoided. This thermal event may hinder detailed understanding of dust mineralogy and geochemistry because the parameters of this flash heating are not well constrained. Models and experiments tend to indicate a high peak temperature, strong thermal gradients and a very fast quench (within a few microseconds). In this study we estimate the parameters of the flash heating based on the interdiffusion of MgO and SiO2 between molten MgO-rich cometary dust particles and the embedding molten aerogel. The presence of a miscibility gap in the MgO-SiO2 binary system precludes full mixing of the Mg-rich melt and the surrounding melted aerogel. The persistence of the two coexisting molten domains, the extend of the MgO contamination of the silica matrix and the shape of the inter-diffusion profile are then used to shed light on the thermal history of cometary dusts particles collected by the spacecraft. Comparison between the models and experimental work will be detailed, together with potential implications on the thermal alteration (intensity of heating and kinetics) of cometary grains during their capture.

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