Binary Near-Earth Asteroid Formation from Rotational Disruption of Gravitational Aggregates

引力聚集体旋转破坏形成的双星近地小行星

• 批准号: 0708110
• 负责人: Derek Richardson
• 金额: $ 24.1万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2010-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0708110&HistoricalAwards=false
• 关键词: Binary; Near; Earth; Asteroid; Formation

AST 0708110RichardsonDr. Derek Richardson, University of Maryland, will carry out a research program aimed at understanding the origin and evolution of binary near-Earth asteroids (NEAs). In previous NSF funded work, the research team established the binary NEA formation efficiency based on tidal encounters of fragile asteroids with Earth over a wide range of encounter parameters. They established that the steady-state number of binaries formed in this way is at most 2% of the total number of NEAs, compared to the observed 15%. This is motivation to determine whether improvements to the model or a new model entirely (such as thermally induced spin-up) is required to fully explain the observations. Four tasks will be carried out: 1) long-term integration of simulated binaries, including study of component shape effects, tidal evolution, and effect of realistic NEA orbits, to improve the sophistication of the steady-state model; 2) investigation of the effect of particle size/shape and aggregate strength on binary formation following rotational disruption, to assess which aspects enhance and which suppress binary formation; 3) determination of the efficiency of binary formation, incorporating results from Tasks 1 and 2; and 4) maintenance and dissemination of a public database of observations and simulations. The research team has developed a tool that quickly provides predictions of steady-state populations of binaries, including pre-existing binaries migrating in from the Main Belt, on the basis of inputs from other simulations. As new simulations are performed, the results are easily incorporated into the predictive algorithm. This provides a powerful way of testing the relative importance of a myriad of physical effects on binary production and evolution. No other group possesses the combination of high-performance simulation tools for gravity and collisions with analysis methods that can address the proposed research. In light of rapidly improving observations and new data from recent and forthcoming spacecraft missions, this theoretical study is an important component of understanding the nature and evolution of small bodies in the solar system.Results from this research are giving insight into the internal structure of NEAs and have implications for hazard mitigation strategies. If the properties of most if not all NEA binaries are consistent with a rotational disruption origin (so far at least some can be accounted for in this way), it will be established that NEAs in general must have very low tensile strength. Overall, a better understanding of NEAs in particular will lead to a better understanding of asteroids in general, and will therefore give insight into the formation and evolution of the building blocks of planets. If NEAs are indeed fragile assemblages of reaccumulated fragments, strategies for mitigating the hazard of such bodies colliding with Earth will be affected, and doubly so now that about 15% of NEAs are known to be binaries. Thus, this study has implications beyond just understanding the origin of binary NEAs. As an outreach component, a public repository of observed binary small bodies will be maintained along with educational resources to explain not only the research at the layman and student levels but also related aspects of small bodies in. The data will be updated on an ongoing basis and submitted to the NASA Planetary Data System annually. At least one new graduate student will join the team over the work period. The research will also build and strengthen partnerships between the Southwest Research Institute (through collaborator Bottke), University of Michigan (through collaborator Scheeres), and the University of Maryland.***

AST 0708110理查森博士马里兰大学的德里克·理查森将开展一项研究计划，旨在了解双星近地小行星(NEA)的起源和演化。在之前美国国家科学基金会资助的工作中，研究小组基于脆弱的小行星与地球在广泛的相遇参数范围内的潮汐相遇，建立了双星近地天体的形成效率。他们确定，以这种方式形成的双星的稳态数量至多占近地天体总数的2%，而观察到的比例为15%。这就是决定是需要对模型进行改进还是需要一个新模型(如热诱导自旋)来完全解释观测结果的动机。将执行四项任务：1)模拟双星的长期积分，包括研究成分形状效应、潮汐演变和实际近地天体轨道的影响，以改进稳态模式的复杂性；2)调查旋转扰动后颗粒大小/形状和聚集强度对双星形成的影响，以评估哪些方面促进双星形成，哪些方面抑制双星形成；3)结合任务1和2的结果，确定双星形成的效率；4)维护和传播观测和模拟公共数据库。研究小组开发了一种工具，可以根据其他模拟的输入，快速预测双星的稳态种群，包括从主带迁入的先前存在的双星。当执行新的模拟时，结果很容易被合并到预测算法中。这提供了一种强有力的方法来测试无数物理效应对双星产生和进化的相对重要性。没有其他小组拥有高性能的重力和碰撞模拟工具与分析方法相结合，可以解决拟议的研究。鉴于来自最近和即将进行的航天器飞行任务的迅速改进的观测和新数据，这项理论研究是了解太阳系小天体的性质和演化的重要组成部分。如果大多数近地天体双星的性质(如果不是全部的话)与旋转破裂起源一致(到目前为止，至少有一些可以用这种方式解释)，就可以确定近地小行星通常具有非常低的抗拉强度。总体而言，尤其是更好地了解近地小行星将有助于更好地了解小行星的一般情况，从而有助于洞察行星的构成要素的形成和演化。如果近地天体确实是再积累的碎片的脆弱组合，那么减轻这类天体与地球碰撞的危险的战略将受到影响，现在已知约15%的近地天体是双星，情况将加倍。因此，这项研究的意义不仅仅在于理解双星近地天体的起源。作为一个外展部分，将与教育资源一起维持一个观察到的双星小体的公共储存库，以不仅解释非专业人员和学生层面的研究，而且还说明小体的相关方面。这些数据将不断更新，并每年提交给美国宇航局行星数据系统。在工作期间，至少有一名新的研究生将加入团队。这项研究还将建立和加强西南研究院(通过合作者Bottke)、密歇根大学(通过合作者Schees)和马里兰大学之间的伙伴关系。