1998 Fiscal Year Final Research Report Summary
In-situ measurement of high velocoty impact fragments of icy planets
| Project/Area Number |
08454134
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
ARAKAWA Masahiko Institute of Low Temperature Science, Hokkaido University, Ins., 低温科学研究所, 助手 (10222738)
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| Co-Investigator(Kenkyū-buntansha) |
KOUCHI Akira Institute of Low Temperature Science, Hokkaido University, Prof., 低温科学研究所, 教授 (60161866)
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| Project Period (FY) |
1996 – 1998
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| Keywords | Icy satellite / Impact process / Shock-wave attenuation / Catastrophic disputation / Reaccumulation |
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| Research Abstract |
High velocity impact among icy planets is an important physical phenomenon related to the planetary accretion process in the outer solar system. Then, an impact experiment on water ice was made by using a micro two-stage light gas gun installed in a cold room (-10ﾟC) to clarify elementary processes of the collisional disruption and to study reaccumulation condition of the impact fragments. As a result, we clarified that the shock pressure attenuated in the ice target according to the relation of P = a (Lp/d)^2 irrespective of the mass ratio between 10^-3 to 10^-5, where Lp is a projectile size and d is a propagation distance. We also observed that the shock wave propagated with the velocity of 4.4 km/s at the shock pressure from 10 to 200 GPa ; 2.6 km/s at 200 MPa. Below 200 MPa, the shear fracture region expanded with the velocity of 1.7 km/s until the shock pressure decreased lower than 60 MPa. The reaccumulation condition of icy planets in the high velocity collisions was estimated to show that fragments disrupted from parent bodies with the radius larger than 500 km could reaccumulate at any conditions of the impact velocity from 500 m/s to 5 km/s and the mass ratio from 10^-2 to l0^-5.
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