SGER: Fracture Processes on Small Extraterrestrial Bodies in the Solar System

SGER：太阳系中小型外星天体的断裂过程

• 批准号: 0202058
• 负责人: Leonid Germanovich
• 金额: $ 5.3万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-02-01 至 2004-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0202058&HistoricalAwards=false
• 关键词: SGER; Fracture; Processes; Small; Extraterrestrial

Leonid GermanovichGeorgia Institute of TechnologySGER: Fracture Processes on Small Extraterrestrial Bodies in the Solar System"Traditionally, asteroids and comets are considered to be an important source of information on the early Solar System. The defense against asteroids and comets has become a popular media and research topic. They pose a risk to life on Earth, but also represent a potential source of metals and other raw materials in the near-Earth space. The vast majority of data concerning asteroids and comets has been obtained via remote observations based on the assumed surface properties, which are functions of former and ongoing geomechanical processes. Yet, there has been no or hardly any quantification and mathematical treatment of the possible role of these processes in the evolution of asteroids and comets.The goal of this proposal is to incorporate principles of terrestrial geomechanics in the framework of mechanical processes that occur on asteroids and comets. Geomechanical processes on terrestrial planets (i.e., Mercury, Venus, Earth, Moon, and Mars) are significantly affected by such factors as gravitation, tectonics, volcanism, and erosion, which are considered absent, or of no consequence, on small extraterrestrial bodies. In essence, asteroids represent the simplest geomechanical systems (no air, no water, extremely low gravity, "primitive" rocks) and studying this extreme case would not only assist astronomical developments but could also provide valuable feedback for conventional (terrestrial) geomechanics.The proposed research consists of three parts: (1) devising a new mathematical model accounting for various temporal and spatial scales associated with fracture processes on asteroids; (2) investigating mechanics of the formation of the soil (regolith) on asteroids; and (3) developing a new model of cometary outbursts associated with fractional sublimation of nucleus material. It is suggested that thermal stresses induced by the "seasonal" periodic heating due to the motion of the asteroid around the Sun in elliptical orbits coupled with short "daily" rotations around the axis of inertia are primarily responsible for the disintegration of asteroid material. Furthermore, the regolith/soil formation is an ongoing process caused by thermal space weathering, which is an effective means of erosion even in the airless, waterless, and low-gravity environment. Finally, sublimation of cometary material caused by crystallization of amorphous ice produces large hydraulic fractures. Propagation of these fractures transports pressurized vapor-dust emulsions to the surface of the comet nucleus resulting in catastrophic vapor-dust outbursts.

Leonid Germanovichgeorgia Technologysger研究所：太阳系中小型外星机体上的断裂过程“传统上，小行星和彗星被认为是早期太阳系的重要信息来源。针对小行星和彗星的防御能力已成为一种受欢迎的媒体和研究主题。他们在地球上构成了生命的风险，但也代表了近地的金属和其他原材料的来源。属性是以前和正在进行的地质力学过程的功能。在小行星和彗星上发生的机械过程框架中的地质力学。在小的外星人身上被认为没有或没有后果。本质上，小行星代表了最简单的地质力学系统（没有空气，没有水，极低的重力，“原始”岩石），研究这种极端情况不仅可以帮助天文学发展，而且还可以为常规（地面）地质力学提供宝贵的反馈。拟议的研究包括三个部分：（1）设计一个新的数学模型，该模型占了与小行星上的断裂过程相关的各种时间和空间尺度； （2）研究小行星上土壤（雷果）形成的力学； （3）开发一种与核材料分数升华相关的彗星爆发的新模型。有人建议，由于“季节性”周期性加热引起的热应力，由于小行星在太阳周围运动椭圆形轨道以及围绕惯性轴围绕的短“每日”旋转的旋转，主要是造成小行星材料的瓦解。此外，岩石/土壤形成是由热空间风化引起的持续过程，即使在无空，无水和低重力环境中，这也是一种有效的侵蚀手段。最后，由无定形冰的结晶引起的彗星材料的升华会产生大型液压裂缝。这些裂缝的传播将加压的蒸气盘乳液传递到彗星核表面，从而导致灾难性的蒸气蒸发。