U.S.-France Cooperative Research: Computing the Real Hazard to the Earth from Comets and Asteroids

这个为期三年的奖项支持美国西南研究所的威廉·F·博特克和尼斯天文台的亚历山德罗·莫比德利在天文学方面的美法合作。该项目研究近地天体或近地天体的起源和演化，近地天体是一群穿过或接近穿过地球轨道的小行星和彗星。目前关于近地天体群体的轨道和大小分布的知识是有限的，因为地球已知的近地天体受到复杂的观测选择效应的影响，而且只发现了整个近地天体群体中的一小部分。美国和法国的研究人员通过开发近地天体无偏轨道和绝对星等分布的量化模型解决了第一个问题。这种合作扩展到新的问题：设计近地天体观测，以确定如何以及在哪里找到最危险或最难找到的近地天体；计算撞击地球和其他类地天体的频率作为撞击能量的函数；计算月球和类地行星上的相对碰撞速率；以及计算长周期和哈雷型彗星数量的上限。法国研究人员为这次合作带来了小行星和彗星动力学以及碰撞碎片物理学方面的专业知识。此外，美国在快速积分代码、大规模数值模拟和轨道演化统计方面的专业知识也起到了补充作用。

0128350BottkeThis three-year award supports U.S.-France collaboration in astronomy between William F. Bottke of the Southwest Research Institute and Alessandro Morbidelli of the Observatory of Nice. The project addresses the origin and evolution of near earth objects or NEOs, a population of asteroids and comets crossing or nearly crossing the Earth's orbit. Present knowledge of orbital and size distributions of the NEO population is limited, because the NEOs known to the Earth are biased by complicated observational selection effects and because only a modest fraction of the entire NEO population has been discovered. US and French researchers addressed the first problem through development of quantitative models of debiased orbital and absolute magnitude distribution of NEOs. This collaboration is extended to new problems: design of NEO surveys to determine how and where to find the most hazardous or hard to find NEOs; computation of frequency of impacts on Earth and other terrestrial bodies as a function of the impact energy; computation of the relative collision rate on the moon and terrestrial planets; and computation of the upper limits on long-period and Halley-type comet population. The French investigators bring to this collaboration expertise in asteroid and cometary dynamics and the physics of collision fragmentation. This is complemented by US expertise in fast integration codes; large scale numerical simulations and statistics on orbital evolution.