ISS Science: Collisions Into Dust Experiment 2 (COLLIDE-2) Results

Results

COLLIDE-2
was returned to Earth by STS-108 on Monday, December 17, 2001. The research
team began de-integrating the hardware, which includes removing the experiment
from its container, removing the videotape, cameras, and data logger,
on January 18, 2002. A visual inspection of the interior revealed that
significant amount of target material had come out of the target chambers,
indicating that the doors had worked. (During COLLIDE, the granular target
material interfered with door function.) The science team reported three
types of impacts: impact with no rebound and no ejecta, impact with no
rebound, but some ejecta, and impact with rebound and ejecta. They were
pleased with COLLIDE-2’s performance and expect good data return.

Applications

Researchers
have conducted collision experiments in ground-based laboratories. However,
to allow material strength rather than gravity to control the experiment
outcome, they have used hypervelocity (several km/s) to simulate dust/particle
collisions. Hypervelocity impacts may have played a role in the creation
of small planetary satellites and planetary rings, but planetary physicists
believe that low-velocity impacts play a crucial role in creating planetary
systems. Dusty regoliths covering particles may have help to dissipate
collisional energy, reducing the rate of mass loss during collisions and
promoting accretional growth of rings, protoplanetary disks, and planetisimals.
Although researchers cannot exactly duplicate dust collisions that naturally
occur in space, microgravity allows them to simulate these conditions
and derive information on the amount, speed, and direction of dust particles
ejected from a deep regolith as a result of low-velocity collisions.

COLLIDE,
and soon COLLIDE-2, has provided the first data on this unexplored area
of collisional parameter space. The data will be placed in the context
of the vast set of ground-based data on high-energy collisions and impacts,
and used to constrain theoretical and numerical models of dust ring evolution
and planetisimal formation. These models help us understand the physical
forces that help create small solar system bodies, planets, and their
rings—objects that populate our solar system and solar systems in
the distant reaches of the universe.

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