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.
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 ringsobjects that populate our solar system and solar systems in the distant reaches of the universe.