Physics of large-scale impacts and planetary evolution

我们的项目分为四组：（1）两个粒子绕太阳运动的碰撞几率研究。(2)实验研究碰撞产物及其碎片的质量、能量和转动分布。(3)结合碰撞实验和化学、同位素测量研究碰撞脱气和碰撞变质作用。(4)利用子项目（1）至（3）的结果研究行星和陨石的形成过程以及行星大气层的起源。在本项目开始之前，这方面的任何研究都没有开展，我们处于非常原始的调查阶段。因此，我们现在无法获得完整的、确定的结果。然而，在获得科学研究资助的三年中，我们得到了一些有趣的和有用的结果，对于子项目（1），我们成功地用数学方法描述了在太阳引力中运动的粒子的统计行为。我们现在正在进行轨道数值计算的研究;结合起来，我们很快就会得到粒子之间碰撞和散射几率的最终和广泛的结果。对于问题（2），我们已经得到了碰撞产物的碰撞行为和碰撞碎片质量分布的一般标度律。对碎片的转动频率分布也有了初步的结果。对于子项目（3），我们进行了初步的实验和化学测量，结果表明除气速率很小，与Ahrens等人的结果相反。最后，对于子项目（4），我们提出了行星大气、地球大气以及金星和火星大气起源的新设想。总的来说，我们现在对这一领域有了全面的了解，今后应该继续研究。

Our projects are divided into four groups:(1) Study on the collisional probability of two particles moving around the Sun.(2) Experimental Study on the products of collisions and mass, energy, and rotational distributions of their fragments.(3) Study on the collisional degassing and collisional metamorphisim combining collision experiments and chemical, isotopical measurements.(4) Studies on the formation processes of the planets and meteorites, and the origin of the planetary atmosphere using the results obtained in subprojects (1) to (3).Before the start of this project, any studies on this field have not been developed and we were in very primitive stage of investigations. Thus, we cannot now have the whole, well-established results. However, during 3 years within which we have been supported by the grant-in-aid for scientific research, we have interesting and useful results for the future studies.As for subproject (1), we have succeeded in formulating mathematically the statistical behavior of the particles moving in the solar gravity. We are now under investigations of numerical orbital calculations; combining we will soon have final and extensive results on the collisional and scattering probabilities between particles. For subject (2), we have already obtained the general scaling law on the collisional behavior of colliding products and on the mass distribution of the collisional fragments. Also we have a preliminary results on the distribution of rotational frequency of the fragments. As to subproject (3), preliminary experiments and chemical measurements have been made with the results that the degassing rate is very small contrary to the result obtained by Ahrens et al. Finally, for subproject (4), we have proposed new scenario on the origin of the planetary atmosphere; terrestrial atmosphere and those of Venus and Mars. As a whole we are now in the course of complete understanding on this field and should continue to investigate in the future.