演講資訊

摘要：

The planet crossing asteroids in the inner solar system have strongly chaotic orbits and the distributions of their angular elements are often regarded as uniform random. We quantified the level of intrinsic non-uniformities of the angular elements for the dynamical subgroups of Near Earth Objects (NEOs) and Mars Crossing Objects (MCOs). Using the methods of angular statistics, we found several statistically significant departures from uniform random angular distributions. These non-uniform distributions of the angular elements may affect the asteroidal impact fluxes on the planets. We developed a new approach that accounts for the non-uniform angular elements of planet crossing asteroids to investigate the impact flux and its seasonal variation on the Earth, the Moon, and Mars. The impact flux of NEOs on the Earth-Moon system is found to be not affected significantly by the non-uniform distribution of angular elements of NEOs. The impact flux on Mars, however, is found to be reduced by a factor of about 2 compared to the flux that would obtain from the assumption of uniform random distributions of the angular elements of MCOs. Moreover, the impact flux on Mars has a strong seasonal variation, with a peak when the planet is near aphelion. We found that the amplitude of this seasonal variation is a factor of 4-5 times smaller compared to what would be obtained with a uniform random distribution of the angular elements of MCOs. We calculate that the aphelion impact flux on Mars is about three times larger than its perihelion impact flux.

Reference URL：

http://www.astro.ncu.edu.tw/people/researcher_bio.php?id=14