GRE阅读高频机经原文：火星的风蚀
<p> 39. 火星的风蚀</p><p> <span word="One">One</span> <span word="reason">reason</span> <span word="researchers">researchers</span> <span word="have">have</span> <span word="long">long</span> <span word="believed">believed</span> <span word="that">that</span> <span word="Mars">Mars</span> <span word="never">never</span> <span word="enjoyed">enjoyed</span> <span word="an">an</span> <span word="extensive">extensive</span> <span word="period">period</span> <span word="of">of</span> <span word="warm">warm</span> <span word="and">and</span> <span word="wet">wet</span> <span word="climate">climate</span> <span word="is">is</span> <span word="that">that</span> <span word="much">much</span> <span word="of">of</span> <span word="the">the</span> <span word="surface">surface</span> <span word="not">not</span> <span word="covered">covered</span> <span word="by">by</span> <span word="wind">wind</span>-<span word="borne">borne</span> <span word="dust">dust</span> <span word="appear">appear</span> <span word="to">to</span> <span word="be">be</span> <span word="composed">composed</span> <span word="of">of</span> <span word="unweathered">unweathered</span> <span word="material">material</span>. <span word="If">If</span> <span word="water">water</span> <span word="flowed">flowed</span> <span word="for">for</span> <span word="an">an</span> <span word="extended">extended</span> <span word="period">period</span>, <span word="researchers">researchers</span> <span word="reasoned">reasoned</span>, <span word="it">it</span> <span word="should">should</span> <span word="have">have</span> <span word="altered">altered</span> <span word="and">and</span> <span word="weathered">weathered</span> <span word="the">the</span> <span word="volcanic">volcanic</span> <span word="minerals">minerals</span>, <span word="creating">creating</span> <span word="clays">clays</span> <span word="or">or</span> <span word="other">other</span> <span word="oxidized">oxidized</span>, <span word="hydrated">hydrated</span> <span word="phases">phases</span> .</p><p> <span word="It">It</span> <span word="turns">turns</span> <span word="out">out</span>, <span word="though">though</span>, <span word="that">that</span> <span word="the">the</span> <span word="scientists">scientists</span> <span word="were">were</span> <span word="not">not</span> <span word="looking">looking</span> <span word="closely">closely</span> <span word="enough">enough</span>. <span word="New">New</span> <span word="high">high</span>-<span word="resolution">resolution</span> <span word="mapping">mapping</span> <span word="data">data</span> <span word="and">and</span> <span word="close">close</span>-<span word="up">up</span> <span word="surface">surface</span> <span word="studies">studies</span> <span word="have">have</span> <span word="revealed">revealed</span> <span word="clays">clays</span> <span word="and">and</span> <span word="other">other</span> <span word="hydrated">hydrated</span> <span word="minerals">minerals</span> <span word="in">in</span> <span word="many">many</span> <span word="regions">regions</span>. <span word="The">The</span> <span word="clay">clay</span> <span word="deposits">deposits</span> <span word="are">are</span> <span word="scattered">scattered</span> <span word="all">all</span> <span word="over">over</span>, <span word="in">in</span> <span word="ancient">ancient</span> <span word="volcanic">volcanic</span> <span word="surfaces">surfaces</span> <span word="and">and</span> <span word="heavily">heavily</span> <span word="cratered">cratered</span> <span word="highland">highland</span> <span word="regions">regions</span>, <span word="some">some</span> <span word="of">of</span> <span word="which">which</span> <span word="have">have</span> <span word="apparently">apparently</span> <span word="been">been</span> <span word="exposed">exposed</span> <span word="by">by</span> <span word="erosion">erosion</span> <span word="only">only</span> <span word="recently">recently</span>.</p><p> </p>
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