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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,Unit 3 Astronomy,What Caused the Late Heavy Bombardment?,1/23,Enjoy the beauty and magnificence of the Universe,2/23,3/23,4/23,Discussion,Are you interested in the Universe and what do you know about it?,Do you know anything about the Late Heavy Bombardment?,5/23,Late Heavy Bombardment,also known as,Lunar Cataclysm,.,6/23,About,4 to 3.8 billion years ago,a period of intense comet and asteroid bombardment is thought to have,pepper,ed all the planets including the Earth.Many of the numerous craters found on the Moon and other bodies in the Solar System record this event.,7/23,One theory holds that a,gravitational surge,caused by the,orbital interaction(轨道相互作用),of,Jupiter,and,Saturn,sent,Neptune,careen,ing,(倾斜),into the,ring of comets(彗星环),in the outer Solar System.The disrupted comets were sent in all directions and collided with the planets.These water-rich objects,may have provided much of the water in the Earths oceans,.,8/23,Introduction,Impact crater,撞击坑、陨石坑,Impact basin 撞击盆地,9/23,asteroid 小行星 comet 彗星,Difference?,小行星主要沿椭圆形轨道运行；彗星除了椭圆形轨道，还能够沿抛物线和双曲线运行。,小行星较稳定，不太轻易挥发物质；彗星在距离太阳较近时，会挥发气体。（彗星成份多为尘埃和冰块）,10/23,meteor/meteorite 流星/流星体,比小行星和彗星更小天体流星体。,Note:,流星是一个天文现象，流星体是太阳系内，小至沙尘，大至巨砾，成为颗粒状碎片。,11/23,Inner solar system,内太阳系，多指太阳、水星(Mercury)、金星(Venus)、地球和火星(Mars)。,Hot water system (,task,:find out the correct translation of the term),12/23,Asteroid belt,(主)小行星带,The,asteroid belt,is the region of the Solar System located roughly,between,the orbits of the planets,Mars and Jupiter,.It is occupied by numerous,irregularly shaped bodies,called asteroids or minor planets.The asteroid belt is,also termed the main asteroid belt or main belt.,13/23,14/23,Near-Earth asteroids(,NEA,s)近地小行星,近地天体(,near-Earth Objects,NEO,)一个。NEO是是轨道距离地球轨道太近(最近距离1.3个天文单位)并所以有可能产生撞击危险小行星、彗星以及大型流星体总称。,天文单位,(astronomical unit)，长度靠近于日地平均距离。,15/23,He has long suspected that two different projectile,population,s have been responsible for cratering inner solar system surfaces.,(stellar)population 星族，指星系中在年纪、化学组成、空间分布、运动特征等方面相近大量天体集合。,16/23,Spacewatch,太空监测计划,SPACEWATCH is the name of a group at the University of Arizonas,Lunar and Planetary Laboratory,founded in,1980,.The primary goal of Spacewatch is,to explore the various populations of small objects in the solar system,and study the statistics of asteroids and comets in order to investigate the,dynamical evolution,(动力学演化)of the solar system.,17/23,Sloan Digital Sky Survey,斯隆数字巡天,The Sloan Digital Sky Survey(SDSS)is one of the most ambitious and influential surveys in the history of astronomy.Over eight years of operations,it obtained deep,multi-color images covering more than a quarter of the sky and created 3-dimensional maps containing more than 930,000 galaxies and more than 120,000,quasars,(类星体).,18/23,Gas Giant Planet 气体巨行星,又名,类木行星,，是不以岩石和固态物质组成巨行星。太阳系有,4,个气体巨行星,木星(Jupiter)、土星(Saturn)、天王星(Uranus)与海王星(Neptune)。,普通大于十倍地球质量行星即为,19/23,Cosmochemistry 宇宙化学,宇宙化学是,研究宇宙物质化学组成及其演化规律,学科，,研究对象,包含陨石、月球、行星系天体、行星际物质、太阳、恒星、星际物质、星系等。,主要,研究内容,有：确定组成宇宙物质元素、同位素和分子，测定其含量。探讨宇宙物质化学演化。这对研究天体起源和生命起源都有主要意义。,20/23,Marine Hydrothemal System深海热泉生态系统,生命起源,可能与热泉生态系统相关。20世纪70年代末，科学家在加拉帕戈斯群岛附近发觉了几处,深海热泉,，在这些热泉里生活着众多生物，这些生物群落生活在,高温,、,高压,、,缺氧,、,偏酸,和,无光,环境中。,部分学者认为，热泉喷口附近环境不但能够为生命出现以及其后生命延续提供所需能量和物质，而且还能够防止地球外物体撞击地球时所造成有害影响，所以热泉生态系统是孕育生命理想场所。,21/23,Yarkovsky Effect 雅克夫斯基效应,这一效应是指小天体因为不均热辐射而取得动能现象。当小行星暴露于太阳光照之下时，其一面,受热升温，热量辐射对应增强，这将产生微弱推进力,。这种力虽小，但作用于小天体，足以对其轨道产生重大影响。,科学家认为，对火星和木星之间小行星带里一些小行星，雅科夫斯基效应会拉近它们与地球距离，增加它们对地球威胁。,22/23,Extensionsomething for fun,阿西莫夫 基地系列,刘慈欣 三体系列,Stargate,Stargate:Atlantis,Battlestar Galactica,23/23,
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