Assessing the risk of potentially hazardous asteroids through mean motion resonances analyses

Abstract

Planetary research on the Near-Earth objects (NEOs) has always been a relevant and meaningful topic. Investigating the dynamical behaviour and physical properties of NEOs is significant for understanding the evolution and origin of the solar system. On the other hand, the study of some of these NEOs is crucial for Earth inhabitants because they experience sufficiently close approaches to our planet and are large enough to cause significant damage in the event of an impact. Potentially hazardous asteroids (PHAs) are those having a minimum orbital intersection distance (MOID) with Earth of less than 0.05 AU and an absolute magnitude of 22 or brighter; some of them could impact the Earth within the next century, causing damage on a regional or larger scale. About 1900 PHAs are currently known, of them only 20 to 30 percent have been found, from estimated amounts to $4700\pm 1500$ . They have orbits which could bring them to collide with our planet except those excluded by protective resonance. Because mean motion resonances can protect the planet-crossing objects from disruptive close encounters or collision with the planets, they provide us a practical approach to assess and mitigate the risk of some PHAs. We introduce a numerical technique STD criterion to seek the PHAs in resonance conveniently. A systematic survey of all the discovered PHAs in mean motion resonance with Earth is presented. The resonant configurations of some PHAs in different orders are depicted to illustrate our results further. We identified 176 PHAs (about 9.3% of discovered PHAs) trapped in resonances with Earth, 70 PHAs among them are currently in resonances while others will be captured into particular resonant configurations. Theoretically, the risk of these 176 PHAs is lower and can be neglected for the 22 PHAs in the long-term stable resonant state. We provide a new approach to assess the risk of PHAs. Our conclusions may provide a significant reference for the space missions devoted to PHAs. We indicate some PHAs in co-orbit resonance with Earth and resonances characterized by asymmetric libration. Our findings also highlight some essential properties of resonant dynamics and provide a number of real examples for the research on resonant configurations and resonance capture.