shape and paricle distribution of rubble-pile asteroid
- Paper number
IAC-10.E1.5.8
- Author
Mr. Yusuke Zemba, University of Tokyo, Japan
- Year
2010
- Abstract
The spacecraft “HAYABUSA” observed an asteroid “ITOKAWA” by a high resolution camera. The observations found out that ITOKAWA was a rubble pile asteroid, which was made up of the rocks piled up. The shape and particle distribution are unique. There are small particles in central part and large particles in both ends. Its unique shape and regolith distribution are caused by composition of universal gravity, friction, centrifugal force by spin and impacts. The impacts are given by collisions of small falling particles. This research object is to reveal the process that “ITOKAWA” reached its present form and particle distribution. Particularly, Brazil nut effect is paid attention to in this research. The effect is one of the segregations of powder and granular material. When different size particles are mixed in a container and it is given vibration, the larger particles rise to the top of the smaller particles. This is because the smaller particle has higher fluidity than the larger one. Firstly, experiments on the ground are conducted. The experiments reveal the conditions that Brazil nut effect occurs. Two different size particles made from glass are put in a PET container. It is shaken by vibration-testing machine. The experiments show how long it takes to rise up to the surface. As the conditions of vibration, amplitude and oscillation period are changed. As the composition of particles, the radius ratio between the larger particles and the smaller ones is changed. Secondly, the behaviors of particles are analyzed by numerical simulation. In this simulation, when the particle is in contact with the other particles, mass-spring-damper model was applied. The results of the simulation are compared with the results of the experiments and the model is verified. Finally, the behaviors of particles shaken by impacts in the space are simulated. It is different from those on the ground. In the space, the particles are not restrained by a container and the earth gravity does not exist. The simulation results are compared with ITOKAWA and the internal structure and the constitution process is revealed.
- Abstract document
- Manuscript document
(absent)