TPO-8 Reading 3 阅读译文

Running Wateron Mars火星上的流水Photographic evidencesuggests thatliquid wateronce existedin greatquantity on thesurface ofMars.Two typesof flowfeatures areseen:runoff channelsand outflowchannels.Runoff channelsare foundin the southern highlands.These flowfeatures areextensivesystems—sometimes hundredsof kilometersin totallength—of interconnecting,twistingchannels thatseem tomerge intolarger,wider channels.They beara strongresemblance toriversystems onEarth,and geologiststhink thatthey aredried-up bedsof long-gone riversthatonce carriedrainfall on Mars fromthe mountainsdown into the valleys.Runoffchannels on Mars speakof atime4billion yearsago theage of the Martianhighlands,when theatmosphere wasthicker,the surfacewarmer,and liquid water widespread.照片证据显示，在火星的表面曾经存在过大量的液态水两种流动形式已经被发现径流沟渠和外流沟渠径流沟渠发现于南部的高地这些流动特征有着庞大的系统——有时竟有数百公里长，这些沟渠相互交错、扭转，并可能汇入更大更宽的沟渠中它们和地球上的河流系统非常相似，地质学家们认为它们是以前曾将火星上的雨水从高山携带到峡谷中的那些河流干涸后的遗迹火星上的径流沟渠存在于40亿年以前就是火星高地的年龄，那时候火星的大气层更厚，地表更暖和，并且液态水分布很广Outflow channelsare probablyrelics ofcatastrophic floodingonMarslong ago.■They appearonly inequatorial regionsand generallydo notform extensiveinterconnectednetworks.■Instead,they areprobably thepaths takenby hugevolumes ofwaterdraining fromthe southernhighlands into the northernplains.・The onrushingwaterarising fromthese flashfloods likelyalso formedthe oddteardrop-shaped“islands”resembling theminiature versionsseen in the wetsand ofour beachesat lowtide thathave been foundon theplains closetotheends of the outflowchannels.■Judging fromthewidth anddepth of the channels,the flowrates musthavebeentruly enormous—perhaps asmuchas ahundred timesgreater thanthe105tons persecond carriedby thegreat Amazonriver.Flooding shapedthe outflowchannels approximately3billion yearsago,about thesametimes asthe northernvolcanic plainsformed.外流沟渠可能是很久以前火星上洪灾的遗迹它们只形成于赤道附近，并一般没有形成广泛交错的网络相反，它们可能是携带大量水从南部高地到北部平原的排水系统由泛滥的洪水而产生的激流也可能形成奇怪的泪滴状小岛就像我们在海水低潮时中湿沙地或海滩上看到的微缩版本一样，已经在靠近外流沟渠末尾处的平原上被看到从这些沟渠的宽度和深度可判断，当时流速一定很大——有可能是亚马逊河每秒钟105吨的流量的一百多倍大约在30亿年以前，北部火山平原形成的同时，洪水改变了外流沟渠的形状Some scientistsspeculate thatMars may have enjoyedan extendedearly Periodduring which rivers,lakes,and perhapseven oceansadorned itssurface.A2003MarsGlobal Surveyorimage showswhat missionspecialists thinkmay bea delta—a fanshapednetworkof channelsand sedimentswhere ariver onceflowed intoa largerbody of water,inthis casea lakefilling acrater inthesouthernhighlands.Other researchersgo evenfurther,suggesting thatthe dataprovide evidence for largeopen expensesofwaterontheearlyMartian surface.A computer-generated viewof the Martian northpolar regionshows theextentof whatmayhavebeen an ancient oceancovering muchofthenorthern lowlands.The HellasBasin,which measuressome3,000kilometers acrossand hasa floorthat liesnearly9kilometers belowthe basinsrim,is anothercandidate foranancientMartian sea.一些科学家认为早期的火星上广泛存在着河流，湖泊甚至是海洋一份2003年的对火星全球的调查照片显示了一个科学家们认为是三角洲的构造——一个扇形的沉积物和水流沟渠的网络，河流可能是从这里流入了一个更大的水体；在这种情况下，它可能是南部高地的一个火山口湖泊其他研究者做了更大胆的猜测，他们认为那些数据表明，早期在火星表面存在大量的水一张关于火星北部极地地区的电脑图片说明有可能有一个古老的海洋覆盖了北部大部分的低洼处那座有大约3,000公里宽，9公里深的希腊盆她也可能是火星海洋These ideasremain controversial.Proponents pointto featuressuch asthe terraced“beaches shownin oneimage,which couldconceivably havebeen leftbehind asa lakeorocean evaporatedand theshoreline receded.But detractorsmaintain thatthe terracescouldalso havebeen createdby geologicalactivity,perhaps relatedtothegeologic forcesthatdepressed theNorthern Hemispherefar belowthe levelofthesouth,in whichcase theyhavenothing whateverto dowith Martianwater.Furthermore,Mars GlobalSurveyor datareleasedin2003seem toindicate thattheMartiansurface containstoo fewcarbonate rocklayers—layers containingcompounds ofcarbon andoxygen—that shouldhave beenformedin abundancein anancient ocean.Their absencesupports thepicture ofa cold,dryMars thatnever experiencedthe extendedmild periodrequired toform lakesand oceans.However,more recentdata implythat atleast someparts ofthe planetdid infact experiencelongperiods inthe pastduringwhichliquid waterexisted onthe surface.这些观点仍然有争议支持者们指出照片里显示的台地“海滩”是由湖泊或者海洋蒸发干涸之后或者海岸线退去之后形成的但是反对者认为这些台地也可能是由于地质活动造成的，也许与使得北半球比南半球地势更低的地质力量有关，在这种情况下，它们就和火星水系没有任何关系此外，2003发布的火星全球调查数据也表明火星表面含有太少的碳化岩层——含有碳氧化合物的岩层——它们应该是在古代海洋中大量形成的这些岩层的缺失支持了火星是一个又冷又干燥的星球，并且不可能拥有形成湖泊和海洋的温和气候这一说法然而，更新的数据表明，至少该星球上的一些部分表面的确在过去很长时间内存在液态水Aside fromsome small-scale gullieschannels foundsince2000,which areinconclusive,astronomers haveno directevidenceforliquidwateranywhere onthe surfaceofMars today,and theamount ofwater vaporintheMartian atmosphereis tiny.Yet evensettingaside theunproven hintsof ancientoceans,the extentofthepast.Where didall thewatergo Theanswer maybe thatvirtually allthe wateronMarsis nowlocked inthepermafrost layerunder thesurface,with morecontained inthe planefspolar caps.除了在2000年发现了一些小规模的、不确定的溪谷以外，宇航员到目前为止还没有在星球的任何地方找到液态水存在的直接证据而且火星大气中水蒸气的含量也微乎其微然而就算不考虑尚未证明的古代海洋存在的线索，外流沟渠的广泛存在就足以证明在火星上曾有大量的水体，水都去了哪里呢？答案可能是实际上火星上所有的水现在已经封存在其地下的永久冻层中，并且在极地地区最多。