英语六级考试备考晨读美文——MARS
<p> <span word="MARS">MARS</span></p><p> <span word="Mars">Mars</span> <span word="According">According</span> <span word="to">to</span> <span word="the">the</span> <span word="best">best</span> <span word="evidence">evidence</span> <span word="gathered">gathered</span> <span word="by">by</span> <span word="space">space</span> <span word="probes">probes</span> <span word="and">and</span> <span word="astronomers">astronomers</span>, <span word="Mars">Mars</span> <span word="is">is</span> <span word="an">an</span> <span word="inhospitable">inhospitable</span> <span word="planet">planet</span>, <span word="more">more</span> <span word="similar">similar</span> <span word="to">to</span> <span word="Earths">Earths</span> <span word="Moon">Moon</span> <span word="than">than</span> <span word="to">to</span> <span word="Earth">Earth</span> <span word="itself">itself</span> - <span word="a">a</span> <span word="dry">dry</span>, <span word="stark">stark</span>, <span word="seemingly">seemingly</span> <span word="lifeless">lifeless</span> <span word="world">world</span>. <span word="Mars">Mars</span> <span word="air">air</span> <span word="pressure">pressure</span> <span word="is">is</span> <span word="equal">equal</span> <span word="to">to</span> <span word="Earths">Earths</span> <span word="at">at</span> <span word="an">an</span> <span word="altitude">altitude</span> <span word="of">of</span> 100,000 <span word="feet">feet</span>. <span word="The">The</span> <span word="air">air</span> <span word="there">there</span> <span word="is">is</span> 95% <span word="carbon">carbon</span> <span word="dioxide">dioxide</span>. <span word="Mars">Mars</span> <span word="has">has</span> <span word="no">no</span> <span word="ozone">ozone</span> <span word="layer">layer</span> <span word="to">to</span> <span word="screen">screen</span> <span word="out">out</span> <span word="the">the</span> <span word="Suns">Suns</span> <span word="lethal">lethal</span> <span word="radiation">radiation</span>. <span word="Daytime">Daytime</span> <span word="temperatures">temperatures</span> <span word="may">may</span> <span word="reach">reach</span> <span word="above">above</span> <span word="freezing">freezing</span>, <span word="but">but</span> <span word="because">because</span> <span word="the">the</span> <span word="planet">planet</span> <span word="is">is</span> <span word="blanketed">blanketed</span> <span word="by">by</span> <span word="the">the</span> <span word="mere">mere</span> <span word="wisp">wisp</span> <span word="of">of</span> <span word="an">an</span> <span word="atmosphere">atmosphere</span>, <span word="the">the</span> <span word="heat">heat</span> <span word="radiates">radiates</span> <span word="back">back</span> <span word="into">into</span> <span word="space">space</span>. <span word="Even">Even</span> <span word="at">at</span> <span word="the">the</span> <span word="equator">equator</span>, <span word="the">the</span> <span word="temperature">temperature</span> <span word="drops">drops</span> <span word="to">to</span> 50 ℃ <span word="at">at</span> <span word="night">night</span>. <span word="Today">Today</span> <span word="there">there</span> <span word="is">is</span> <span word="no">no</span> <span word="liquid">liquid</span> <span word="water">water</span>, <span word="although">although</span> <span word="valleys">valleys</span> <span word="and">and</span> <span word="channels">channels</span> <span word="on">on</span> <span word="the">the</span> <span word="surface">surface</span> <span word="show">show</span> <span word="evidence">evidence</span> <span word="of">of</span> <span word="having">having</span> <span word="been">been</span> <span word="carved">carved</span> <span word="by">by</span> <span word="running">running</span> <span word="water">water</span>. <span word="The">The</span> <span word="polar">polar</span> <span word="ice">ice</span> <span word="caps">caps</span> <span word="are">are</span> <span word="made">made</span> <span word="of">of</span> <span word="frozen">frozen</span> <span word="water">water</span> <span word="and">and</span> <span word="carbon">carbon</span> <span word="dioxide">dioxide</span>, <span word="and">and</span> <span word="water">water</span> <span word="may">may</span> <span word="be">be</span> <span word="frozen">frozen</span> <span word="in">in</span> <span word="the">the</span> <span word="ground">ground</span> <span word="as">as</span> <span word="permafrost">permafrost</span>. <span word="Despite">Despite</span> <span word="these">these</span> <span word="difficult">difficult</span> <span word="conditions">conditions</span>, <span word="certain">certain</span> <span word="scientists">scientists</span> <span word="believe">believe</span> <span word="that">that</span> <span word="there">there</span> <span word="is">is</span> <span word="a">a</span> <span word="possibility">possibility</span> <span word="of">of</span> <span word="transforming">transforming</span> <span word="Mars">Mars</span> <span word="into">into</span> <span word="a">a</span> <span word="more">more</span> <span word="Earth">Earth</span> <span word="like">like</span> <span word="planet">planet</span>. <span word="Nuclear">Nuclear</span> <span word="reactors">reactors</span> <span word="might">might</span> <span word="be">be</span> <span word="used">used</span> <span word="to">to</span> <span word="melt">melt</span> <span word="frozen">frozen</span> <span word="gases">gases</span> <span word="and">and</span> <span word="eventually">eventually</span> <span word="build">build</span> <span word="up">up</span> <span word="the">the</span> <span word="atmosphere">atmosphere</span>. <span word="This">This</span> <span word="in">in</span> <span word="turn">turn</span> <span word="could">could</span> <span word="create">create</span> <span word="a">a</span> <span word="greenhouse">greenhouse</span> <span word="effect">effect</span> <span word="that">that</span> <span word="would">would</span> <span word="stop">stop</span> <span word="heat">heat</span> <span word="from">from</span> <span word="radiating">radiating</span> <span word="back">back</span> <span word="into">into</span> <span word="space">space</span>. <span word="Liquid">Liquid</span> <span word="water">water</span> <span word="could">could</span> <span word="be">be</span> <span word="thawed">thawed</span> <span word="to">to</span> <span word="form">form</span> <span word="a">a</span> <span word="polar">polar</span> <span word="ocean">ocean</span>. <span word="Once">Once</span> <span word="enough">enough</span> <span word="ice">ice</span> <span word="has">has</span> <span word="melted">melted</span>, <span word="suitable">suitable</span> <span word="plants">plants</span> <span word="could">could</span> <span word="be">be</span> <span word="introduced">introduced</span> <span word="to">to</span> <span word="build">build</span> <span word="up">up</span> <span word="the">the</span> <span word="level">level</span> <span word="of">of</span> <span word="oxygen">oxygen</span> <span word="in">in</span> <span word="the">the</span> <span word="atmosphere">atmosphere</span> <span word="so">so</span> <span word="that">that</span>, <span word="in">in</span> <span word="time">time</span>, <span word="the">the</span> <span word="planet">planet</span> <span word="would">would</span> <span word="support">support</span> <span word="animal">animal</span> <span word="life">life</span> <span word="from">from</span> <span word="Earth">Earth</span> <span word="and">and</span> <span word="even">even</span> <span word="permanent">permanent</span> <span word="human">human</span> <span word="colonies">colonies</span>. <span word="This">This</span> <span word="was">was</span> <span word="once">once</span> <span word="thought">thought</span> <span word="to">to</span> <span word="be">be</span> <span word="so">so</span> <span word="far">far</span> <span word="in">in</span> <span word="the">the</span> <span word="future">future</span> <span word="as">as</span> <span word="to">to</span> <span word="be">be</span> <span word="irrelevant">irrelevant</span>, <span word="said">said</span> <span word="Christopher">Christopher</span> <span word="McKay">McKay</span>, <span word="a">a</span> <span word="research">research</span> <span word="scientist">scientist</span> <span word="at">at</span> <span word="the">the</span> <span word="National">National</span> <span word="Aeronautics">Aeronautics</span> <span word="and">and</span> <span word="Space">Space</span> <span word="Administration">Administration</span>. <span word="But">But</span> <span word="now">now</span> <span word="its">its</span> <span word="starting">starting</span> <span word="to">to</span> <span word="look">look</span> <span word="practical">practical</span>. <span word="We">We</span> <span word="could">could</span> <span word="begin">begin</span> <span word="work">work</span> <span word="in">in</span> <span word="four">four</span> <span word="or">or</span> <span word="five">five</span> <span word="decades">decades</span>. <span word="The">The</span> <span word="idea">idea</span> <span word="of">of</span> <span word="terra">terra</span> <span word="forming">forming</span> <span word="Mars">Mars</span>, <span word="as">as</span> <span word="enthusiasts">enthusiasts</span> <span word="call">call</span> <span word="it">it</span>, <span word="has">has</span> <span word="its">its</span> <span word="roots">roots</span> <span word="in">in</span> <span word="science">science</span> <span word="fiction">fiction</span>. <span word="But">But</span> <span word="as">as</span> <span word="researchers">researchers</span> <span word="develop">develop</span> <span word="a">a</span> <span word="more">more</span> <span word="profound">profound</span> <span word="understanding">understanding</span> <span word="of">of</span> <span word="how">how</span> <span word="Earths">Earths</span> <span word="ecology">ecology</span> <span word="supports">supports</span> <span word="life">life</span>, <span word="they">they</span> <span word="have">have</span> <span word="begun">begun</span> <span word="to">to</span> <span word="see">see</span> <span word="how">how</span> <span word="it">it</span> <span word="may">may</span> <span word="be">be</span> <span word="possible">possible</span> <span word="to">to</span> <span word="create">create</span> <span word="similar">similar</span> <span word="conditions">conditions</span> <span word="on">on</span> <span word="Mars">Mars</span>. <span word="Dont">Dont</span> <span word="plan">plan</span> <span word="on">on</span> <span word="homesteading">homesteading</span> <span word="on">on</span> <span word="Mars">Mars</span> <span word="any">any</span> <span word="time">time</span> <span word="soon">soon</span>, <span word="though">though</span>. <span word="The">The</span> <span word="process">process</span> <span word="could">could</span> <span word="take">take</span> <span word="hundreds">hundreds</span> <span word="or">or</span> <span word="even">even</span> <span word="thousands">thousands</span> <span word="of">of</span> <span word="years">years</span> <span word="to">to</span> <span word="complete">complete</span>, <span word="and">and</span> <span word="the">the</span> <span word="cost">cost</span> <span word="would">would</span> <span word="be">be</span> <span word="staggering">staggering</span>.</p>
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