Observational studies of small solar system bodies: origins, dynamics and structure

太阳系中的小天体(小行星、彗星、半人马和跨海王星天体)是我们太阳系形成阶段的遗迹。在许多情况下，它们含有未经实质性加工的原始材料。它们的物理结构、化学和动力学演化为了解早期太阳系提供了一个独特的窗口，为我们的太阳系和其他行星系统的形成模型提供了信息。 这些天体的碎片偶尔会撞击地球大气层，以流星的形式产生电离、辐射和冲击。通过研究碎片(流星体)如何在大气中消融，我们可以重建其性质(体积密度、强度、颗粒大小)，进而了解其母体。 这一提议的方法是通过记录它们的光、电离和激波产生来观察大小从尘埃颗粒到巨石的流星体与大气的相互作用。通过测量它们的质量和各种大小的数量，我将准确地估计这些天体到地球的流量。对于较小的流星体，这将有助于精炼地球积累的流星物质的数量。对于较大的物体(米-分米尺度)，我将测量它们的冲击效果，特别是冲击强度，因为这是限制火球如何在地面造成破坏的关键。2015年2月15日车里雅宾斯克空难发生在俄罗斯上空后，迫切需要更好的地面破坏模型，以便在撞击前检测到另一个多米大小的近地物体时，帮助告知民防官员。对于这些较大的事件，陨石的发现也为前兆天体的成分和结构提供了“地面真相”。如果我们能够同时记录大气层中的火球，这种更大的撞击器也构成了对进入模型的最终校准。通过模拟大气中各种大小的碎裂行为，我将测量大量流星体的强度和体积密度，并将其与撞击前的轨道相关联。结果将是尘埃到巨石大小的物体与地球碰撞的强度/结构和轨道起源的详细协调图片。最终，这将从尘埃和较大的近地天体(NEO)两个方面建立起一幅近地空间小型天体的起源和目前生态的图景。由此产生的尘埃数量和物理特征与地球附近巨石大小的流星体有关的“路线图”对于行星防御和保护航天器免受流星体撞击具有实际意义。这些信息也需要用于即将到来的航天器任务，如NASA小行星重定向任务，该任务旨在将一块巨石大小的岩石从近地小行星返回月球轨道。

The small bodies in the solar system (asteroids, comets, centaurs and trans-Neptunian objects) are relics from the formation stage of our solar system. In many cases they contain primitive material which has not experienced substantial processing. Their physical structure, chemistry and dynamical evolution offer a unique window into the early solar system informing formation models of our solar system and other planetary systems. Fragments of these bodies occasionally impact the Earth’s atmosphere, producing ionization, radiation and shocks in the form of “meteors”. By studying how the fragment (meteoroid) ablates in the atmosphere we can reconstruct its properties (bulk density, strength, grain sizes) and by extension learn about its parent body. The approach of this proposal is to observe meteoroids ranging in size from dust grains to boulders interacting with the atmosphere by recording their light, ionization and shock production. By measuring their mass and numbers at all sizes I will accurately estimate the flux of these bodies to Earth. For smaller meteoroids this will help in refining the amount of meteoritic material accumulated by the Earth. For larger objects (meter-decameter-scale) I will measure their impact effects, particularly shock strength, as this is critical to constraining how fireballs can cause damage at the ground. In the wake of the Feb 15, 2015 Chelyabinsk airburst over Russia there is a pressing need for better ground damage models to help inform civil defence officials in the event another multi-meter sized near-Earth object is detected just prior to impact. For these larger events, recovery of meteorites also provides “ground-truth” for precursor body composition and structure. Such larger impactors also form the ultimate calibration for entry models, if we are able to simultaneously document the fireball in the atmosphere. Through modelling of the breakup behavior in the atmosphere at all sizes I will measure the strength and bulk density of a large number of meteoroids and correlate this with their pre-impact orbits. The result will be a detailed coordinated picture of the strength/structure and orbital origins for dust-to-boulder sized objects colliding with the Earth. Ultimately this will build up a picture of the origins and present ecology of small bodies in near-Earth space both in terms of dust and larger Near-Earth Objects (NEOs). The resulting “road-map” of the number and physical characteristics of dust to boulder sized meteoroids near Earth is of practical importance for planetary defence and for the protection of spacecraft from meteoroid impacts. This information is also needed for upcoming spacecraft missions such as the NASA Asteroid Redirect Mission, which seeks to return a boulder-sized rock to lunar orbit from a near-Earth asteroid.