Interpretation of Wild 2 dust fine structure: Comparison of Stardust aluminum foil craters to the three-dimensional shape of experimental impacts by artificial aggregate particles and meteorite powders
Article first published online: 26 JAN 2010
2009 The Meteoritical Society
Meteoritics & Planetary Science
Volume 44, Issue 10, pages 1489–1509, October 2009
How to Cite
Kearsley, A. T., Burchell, M. J., Price, M. C., Graham, G. A., Wozniakiewicz, P. J., Cole, M. J., Foster, N. J. and Teslich, N. (2009), Interpretation of Wild 2 dust fine structure: Comparison of Stardust aluminum foil craters to the three-dimensional shape of experimental impacts by artificial aggregate particles and meteorite powders. Meteoritics & Planetary Science, 44: 1489–1509. doi: 10.1111/j.1945-5100.2009.tb01188.x
- Issue published online: 26 JAN 2010
- Article first published online: 26 JAN 2010
- Received 11 March 2009; revision accepted 14 September 2009
Abstract— New experimental results show that Stardust crater morphology is consistent with interpretation of many larger Wild 2 dust grains being aggregates, albeit most of low porosity and therefore relatively high density. The majority of large Stardust grains (i.e. those carrying most of the cometary dust mass) probably had density of 2.4 g cm−3 (similar to soda-lime glass used in earlier calibration experiments) or greater, and porosity of 25% or less, akin to consolidated carbonaceous chondrite meteorites, and much lower than the 80% suggested for fractal dust aggregates. Although better size calibration is required for interpretation of the very smallest impacting grains, we suggest that aggregates could have dense components dominated by μm-scale and smaller sub-grains. If porosity of the Wild 2 nucleus is high, with similar bulk density to other comets, much of the pore space may be at a scale of tens of micrometers, between coarser, denser grains.
Successful demonstration of aggregate projectile impacts in the laboratory now opens the possibility of experiments to further constrain the conditions for creation of bulbous (Type C) tracks in aerogel, which we have observed in recent shots. We are also using mixed mineral aggregates to document differential survival of pristine composition and crystalline structure in diverse finegrained components of aggregate cometary dust analogues, impacted onto both foil and aerogel under Stardust encounter conditions.