首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Was the Red Planet once a wet planet? A plucky Martian rover finally delivers some hard evidence. Giovanni Schiaparelli coul
Was the Red Planet once a wet planet? A plucky Martian rover finally delivers some hard evidence. Giovanni Schiaparelli coul
admin
2012-02-24
32
问题
Was the Red Planet once a wet planet? A plucky Martian rover finally delivers some hard evidence.
Giovanni Schiaparelli could have told you there had been water on Mars. It was Schiaparelli who peered through his telescope one evening in 1877 and discovered what he took to be the Red Planet’s famous canals. As it turned out, the canals were an optical illusion, but as more powerful telescopes and, later, spacecraft zoomed in for closer looks, there was no shortage of clues suggesting that Mars was once awash in water. Photographs shot from orbit show vast plains that resemble ancient sea floors, steep gorges that would dwarf the Grand Canyon and sinuous surface scars that look an awful lot like dry riverbeds.
Given all that, why were NASA scientists so excited last week to announce that one of their Mars rovers, having crawled across the planet for five weeks, finally determined that Mars, at some point in its deep past, was indeed "drenched"—to use NASA’s term—with liquid water?
Part of their excitement probably stems from sheer failure fatigue. NASA has had its share of setbacks in recent years—including a few disastrous missions to Mars. So it was with some relief that leading investigator Steve Squyres announced that the rover Opportunity had accomplished its primary mission. "The puzzle pieces have been falling into place," he told a crowded press conference, "and the last piece fell into place a few days ago."
But there was also, for the NASA team, the pleasure that comes from making a genuine contribution to space science. For despite all the signs pointing to Mars’ watery past, until Opportunity poked its instruments into the Martian rocks, nobody was really sure how real that water was. At least some of the surface formations that look water carved could have been formed by volcanism and wind. Just two years ago, University of Colorado researchers published a persuasive paper suggesting that any water on Mars was carried in by crashing comets and then quickly evaporated.
The experiments that put that theory to rest—and nailed down the presence of water for good—were largely conducted on one 10-in.-high, 65-ft.-wide rock outcropping in the Meridiani Planum that mission scientists dubbed El Capitan. The surface of the formation is made up of fine layers—called parallel laminations—that are often laid down by minerals settling out of water. The rock is also randomly pitted with cavities called vugs that created when salt crystals form in briny water and then fall out or dissolve away.
Chemical analyses of El Capitan, performed with two different spectrometers, support the visual evidence. They show that it is rich in sulfates known to form in the presence of water as well as a mineral called jarosite, which not only forms in water but also actually contains a bit of water trapped in its matrix.
The most intriguing evidence comes in the form of the BB-size spherules—or "blueberries," as NASA calls them—scattered throughout the rock. Spheres like these can be formed either by volcanism or by minerals accreting under water, but the way the blueberries are mixed randomly through the rock—not layered on top, as they would have been after a volcanic eruption—strongly suggests the latter.
None of these findings are dispositive, but their combined weight persuaded NASA scientists to summarize their findings in unusually explicit language. "We have concluded that the rocks here were soaked with liquid water," said Squyres flatly. "The ground would have been suitable for life."
Does that mean that there was—or still is—life on Mars? The fossil record on Earth suggests that given enough time and H20, life will eventually emerge, but there’s nothing in the current findings to prove that this happened on Mars. Without more knowledge of such variables as temperature, atmosphere and the length of time Martian water existed, we can’t simply assume that what happened on our planet would necessarily occur on another.
Opportunity and its twin robot Spirit are not equipped to search for life. Their mission is limited to looking for signs of water. But there’s still a lot for them to do. Just knowing that rocks were wet doesn’t tell you if the water was flowing or stationary, if it melted down from ice caps or seeped up through the ground. And if water was once there in such abundance, where did it go? Opportunity, which is very likely to exceed its planned 90-day mission, is already looking for those answers, toddling off to investigate other rocks farther and farther from its landing site. Spirit is conducting its own studies in Gusev Crater, on the opposite side of the planet.
The next step—the search for life—will have to wait until 2013 or so. That’s when NASA has tentatively scheduled the first round trip to Mars—a mission that will pluck selected rocks off the Red Planet and bring them back home for closer study. Whether humans will ever follow those machines—President Bush’s January announcement notwithstanding—is impossible to say.
According to the passage, the formations on the surface of Mars could have been formed by the following except ______.
选项
A、wind
B、volcanoes
C、earthquakes
D、water brought by comets
答案
C
解析
由第四段可知,选项A、B和D都被提及,而C没有被提及,故C为正确答案。
转载请注明原文地址:https://jikaoti.com/ti/bZjYFFFM
0
专业英语八级
相关试题推荐
A、BritainB、FranceC、FinlandD、SwitzerlandB
SamuelSlaterwasborninBelper,England,in1768.OncompletionofhissevenyearapprenticeshipinanEnglishspinningmill,
RainmakingScientificrainmakingwasstartedbyVincentJ.Schaeferaftertheyearof【1】.Alucky【2】broughthimtosuccess.
IstoodatthewirefenceintheedgeofHilario’spastureand【M1】______watchedtheRussiansforlongtime,untilmostoftheo
我的最大爱好是深思默想。我可以一个人长时间地独处而感到愉快。独享欢乐是一种愉快,独自忧伤也是一种愉快。孤独的时候,精神不会是一片纯粹的空白,它仍然是一个丰富多彩的世界。情绪上的大欢乐和大悲痛往往都在孤独中产生。孤独中,思维可以不依照逻辑进行。孤独更多地产生
Extraordinarycreativeactivityhasbeencharacterizedasrevolutionary,flyinginthefaceofwhatisestablishedandproducing
Theworldisinaself-destructionmode.BythisstatementImeanthatthepeopleoftheworldarebentonmakingthisplanetin
A、Adriver.B、Apassenger.C、Apoliceman.D、doctor.C
人生是由“渐”维持的。这在女人恐怕尤为必要:歌剧中,舞台上如花的少女,就是将来火炉旁边的老婆子,这句话骤听使人不能相信,少女也不肯承认,实则现在的老婆子都是由如花的少女“渐渐”变成的。人之能堪受境遇的变衰,,也全靠这“渐”的助力。巨富的纨绔子弟因屡
ThewetvolcanicashthatcoveredaMayavillageinCentralAmericainaboutAD595coatedandpreservedeverydayobjectsbeans,
随机试题
医疗事故的处理原则是
A.输血B.泼尼松C.睾酮D.切脾自身免疫性溶血性贫血首选
女患者,30岁,带下量多,色白质粘,无臭气,神疲肢倦,纳少便溏,面色萎黄,舌淡,苔白腻,脉缓弱,治疗最佳方剂是:
有关齿状线解剖意义的描述中,错误的是
图示刚架中,若将作用于B处的水平力P沿其作用线移至C处,则A、D处的约束力:
某建筑工程建筑面积25万m2,混凝土现浇结构,筏形基础,地下3层,地上12层,基础埋深12.4m,该工程位于繁华市区,施工场地狭小。工程所在地区地势北高南低,地下水流从北向南。施工单位的降水方案计划在基坑南边布置单排轻型井点。基坑开挖到设计标高后,施
下列关于归属于少数股东的外币报表折算差额在母公司合并资产负债表的列示方法中,不正确的有()。
公安机关执法勤务机构实行队建制,称为()。
电子商务交易必须具备抗抵赖性,目的在于防______。
有如下程序inta[10]={1,2,3,4,5,6,7,8,9,10};int*p=&a[3],b;b=p[5];则b的值是
最新回复
(
0
)