Experimental studies on the aggregation properties of ice and dust in planet-forming regions

Heißelmann, Daniel; Fraser, Helen J. and Blum, Jürgen (2007). Experimental studies on the aggregation properties of ice and dust in planet-forming regions. In: 58th International Astronautical Congress, 24-28 Sep 2007, Hyderabad, India.

URL: http://www.iafastro.net/iac/archive/

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 45th 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.

Viewing alternatives

Item Actions

Export

About

Recommendations