资源描述：
《职称英语理工类必考》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、阅读理解*第三＋八篇"LifeFormFound"onSaturn'sTitanScientistssaytheyhavediscoveredhintsofalienlife1ontheSaturn'smoon2.ThediscoveryofasortoflifewasannouncedafterresearchersattheUSspaceagency,NASA3,analyzeddatafromspacecraftCassini4,whichpointedto,theexistenceofmethane-b
2、asedformoflifeonSaturn'sbiggestmoon.Scientistshavereportedlydiscoveredcluesshowingprimitivealienbeingsare"breathing"inTitan'sdenseatmospherefilledwithhydrogen.TheyarguethathydrogengetsabsorbedbeforehittingTitan'splanet-likesurfacecoveredwithmethanelakesandri
3、vers.This,theysay,pointstotheexistenceofsome"bugs"5consumingthehydrogenatthesurfaceofthemoonlessthanhalfthesizeoftheEarth."Wesuggestedhydrogenconsumptionbecauseit'stheobviousgasforlifetoconsumeonTitan,similartothewayweconsumeoxygenonEarth,"saysNASAscientistC
4、hrisMcKay."Ifthesesignsdoturnouttobeasignoflife,itwouldbedoublyexcitingbecauseitwouldrepresentasecondformoflifeindependentfromwater-basedlifeonEarth."Todate,scientistshavenotyetdetectedthisformoflifeanywhere,thoughthereareliquid-water-basedmicroorganismsonEa
5、rththatgrowwellonmethaneorproduceitasawasteproduct.OnTitan,wheretemperaturesarearound90Kelvin6(minus290degreesFarenheit),amethanebasedorganismwouldhavetouseasubstancethatisliquidasitsmediumforlivingprocesses,butnotwateritself.WaterisfrozensolidonTitan'ssurfa
6、ceandmuchtoocoldtosupportlifeasweknowit.ScientistshadexpectedtheSun'sinteractionswithchemicalsintheatmospheretoproduceacoatingofacetyleneonTitan'ssurface.ButCassinidetectednoacetyleneonthesurface.TheabsenceofdetectableacetyleneontheTitan'ssurfacecanverywellh
7、aveanon-biologicalexplanation,saidMarkAllen,aprincipalinvestigator7oftheNASATitanteam."Scientificconservatismsuggeststhatabiologicalexplanationshouldbethelastchoiceafterallnon-biologicalexplanationsareaddressed,"Allensaid."Wehavealotofworktodotoruleout8possi
8、blenon-biologicalexplanations.Itismorelikelythatachemicalprocess,withoutbiology,canexplaintheseresults."练习：1.WhathavescientistsfoundaboutSaturn?CTheyhavefoundmethane-basedlifeonTitan.2.Whatdosci
