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Could life have existed during earths early history

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Could life have existed during Earth’s early history? The vast majority of these collisions occurred in the first few hundred million years of our solar system’s history (heavy bombardment) On planets and moons with solid surfaces, such collisions leave impact craters as visible scars
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The most heavily cratered regions are the lunar highlands, where craters are so abundant that we see overlapping crater boundaries and craters on top of other craters We see relatively few craters in the regions known as the lunar maria Late heavy bombardment around 3.9 billion years ago Planetary scientists can use simple counts of craters on other worlds to estimate the ages of the surfaces Given the evidence of continents and oceans all the way back to 4.4 to 4.5 billion years ago, there seems no reason why life could not have arisen during the Hadean Impact of an asteroid more than about 350-400 km across would provide surface temperature to as high as 2,000 degrees C (3,600 degrees F) It is unlikely that any life could survive such effects, so we conclude that an impact of that size would be a sterilizing impact – one that would kill off all life on the planet Conclusion: While conditions may have allowed life to arise during the Hadean, perhaps even as far back as 4.4 to 4.5 billion years ago, most or all of this life would have been wiped out by major impacts. What is the Earth like in the inside? Only been 6,400 km to Earth’s center Learn much about Earth’s internal structure from study of seismic waves Precise speed and direction of seismic waves depend on the composition, density, pressure, temperature, and phases of the material they pass through Core: the highest-density material, consisting primarily of nickel and iron Inner core and outer core Mantle: rocky material of moderate density Crust: lowest-density rock Earth’s outer layer – lithosphere – cool and rigid rock Mantle rock flows with a characteristic pattern called convection, in which hot material expands and rises while cooler material contracts and falls Convection creates convection cells Differentiation: materials separate according to their density Conclusion: Internal heat allows the mantle rock to convect slowly. How does play tectonics shape Earth’s surface? Earth is the only planet with ongoing plate tectonics According to the theory, the lithosphere fractured because of stresses generated by mantle convection, and the resulting plates now essentially “float” over the mantle, gradually moving over, under, and around each other as convection moves Earth’s interior rocks GPS measurements offer most direct evidence of plate motion Evidence of past continental motion, evidence that plates spread apart on seafloors, and a difference between the nature of the Earth’s crust on the seafloors and the continents Wegener – continental drift Seafloor spreading and continental motion
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Could life have existed during Earths early history The...

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