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EXPERIMENT TO SIMULATE IMPACT INTO LOW-DENSITY ASTEROIDS

模拟低密度小行星撞击的实验

基本信息

批准号：
12640412
负责人：
FUJIWARA Akira
金额：
$ 2.24万
依托单位：
THE INSTITUTE OF SPACE AND ASTRONAUTICAL SCIENCE (ISAS)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640412/
关键词：
ASTEROID HYPERVELOCITY IMPACT REGOLITH 低密度物質衝突クレーター

项目摘要

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.

进行实验和理论研究是为了了解小行星表面是否存在风化层。风化层是由陨石体高速撞击喷出的碎片堆积而成的。其速度低于逃逸速度。我们通过实验和理论确定了撞击所喷射碎片的速度。特别是由于最近来自太空任务的报告表明存在密度非常低的小行星，我们考虑到了这一点。靶体由加热烧结的玻璃珠制成。通过改变烧结时间，可以得到约4％至80％的孔隙率。直径2毫米至7毫米的尼龙弹丸以3-★公里/秒的速度撞击目标。高速摄像机记录了撞击现象。大多数碎片沿着目标表面法线喷射，并测量了它们在地板上的着陆位置和目标上的弹坑形状。根据前面的测量，获得了速度小于约 20 m/s 时的片段速度-尺寸分布。定量结果表明，碎片速度随着孔隙率的增加而降低。同时还发现，在孔隙率约为40%时，弹坑直径达到最大值。根据这些结果，建立了速度-尺寸分布的比例定律，并利用这次的数值方法研究了小行星风化层厚度的发展。结果发现，即使在10-1公里大小的小行星上也存在风化层，为弱强度物质。这些结果与最近近舒梅克航天器获得的事实相符，即 433 Eros 表面有风化层。