| Project/Area Number |
12640412
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体地球物理学
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| Research Institution | THE INSTITUTE OF SPACE AND ASTRONAUTICAL SCIENCE (ISAS) |
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Principal Investigator |
FUJIWARA Akira THE INSTITUTE OF SPACE AND ASTRONAUTICAL SCIENCE, PROFESSOR, 惑星研究系, 教授 (70173482)
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| Co-Investigator(Kenkyū-buntansha) |
ABE Masanao THE INSTITUTE OF SPACE AND ASTRONAUTICAL SCIENCE, RESEARCH ASSOCIATE, 惑星研究系, 助手 (00270439)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2001: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2000: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | ASTEROID / HYPERVELOCITY IMPACT / REGOLITH / 低密度物質 / 衝突 / クレーター |
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| Research Abstract |
Experimental and theoretical studies were performed to understand whether regolith exists or not on the asteroid surface. The regolith is formed by accumulation of the fragments wliich are ejected by high-velocity impacts of meteoritic bodies but. whose velocity is lower than the escape velocity. We determined velocity of the fragments ejected by the impact both experimentally and theoretically. Especially since recent reports from space missions shows the existence of asteroids of very low density, we take this point into account. Target bodies were made of glass beads sintered by heating. Porosity of about 4 to 80 per cent was made by changing the sintering period. Nylon projectiles of 2 mm to 7 mm in diameter were impacted to the targets at velocity 3-★km/s. Impact phenomena were recorded by high-speed cameras. Most of fragments were ejected along the target surface normal, and the location of their landing site on the floor and crater shape on the targets were measured. From the former measurement fragment velocity-size distribution at the velocity less than about 20 m/s was obtained. It was shown quantitatively that fragment velocity decreases with increasing of porosity.
Also found was that the crater diameter has a maximum at porosity of about 40 per cent. From these results a scaling law of velocity-size distribution was constructed and using this time development of asteroid regolith thickness was pursued by numerical method. As the result it was found that, regolith exists even on the asteroids of 10 - 1 km in size for the weak strength material. These results are compatible with the fact obtained by recent Near-Shoemaker spacecraft that 433 Eros has regolith on its surface.
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