Experimental Studies on the Aggregation Properties of Ice and Dust in Planet-Forming Regions
- Paper number
IAC-07-A2.1.02
- Author
Mr. Daniel Heißelmann, Technical University of Braunschweig, Germany
- Coauthor
Helen J. Fraser, University of Strathclyde, United Kingdom
- Coauthor
Jürgen Blum, Germany
- Year
2007
- Abstract
To investigate the second stage of formation of protoplanets up to kilometre size which is still not understood, we built a setup for collision experiments with millimetre-sized, highly porous dust aggregates. The experiments, which were successfully conducted at ambient temperature during ESA’s 45 th Parabolic Flight Campaign, are the first in a series of at least three parabolic flight campaigns. The recent experiment probed the sticking and collision behaviour of dust aggregates (composed of 1.5 µm-sized monodisperse SiO 2 grains) from which planetesimals and cometary nuclei are considered to have formed. In the parabolic flights, pairs of fragile dust aggregates were collided under microgravity conditions at relative velocities between ∼ 25 cm/ s and ∼ 40 cm/ s using a set of pistons driven at constant acceleration. Additionally, fragile aggregates were impacted on a dusty target screen, simulating protoplanetary collisions with larger bodies. The collision events happened at random impact angle and were recorded by ESA’s IMPACT Camera and Digital Recording System, a high–speed, high–resolution digital camera.
The majority of both the particle-target and aggregate-aggregate collisions showed a quasi-elastic rebounding behaviour. Whereas ∼ 10 % of the particle-target collisions resulted in sticking (of sub-millimetre-sized fragments only), the other key effect in ∼ 10 % of the aggregate-aggregate collisions was fragmentation. The measured coefficient of restitution for the bouncing collisions indicates that the residual translational energy is ∼ 5 % of the primal energy of the aggregates’ motion for central collisions and increases with increasing impact parameter.
During future Parabolic Flight Campaigns, the experimental work will be extended to collisions of dust aggregates at lower temperatures (80−220 K) and of solid ice particles and icy aggregates at cryogenic temperatures (below ∼ 140 K) corresponding to the conditions found in the outer solar nebula at 5−30 AU.
- Abstract document
- Manuscript document
IAC-07-A2.1.02.pdf (🔒 authorized access only).
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