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 could
Was the Red Planet once a wet planet? A plucky Martian rover finally delivers some hard evidence. Giovanni Schiaparelli could
admin
2020-05-01
29
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 H
2
O, 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.
The fact that there was water on Mars brings NASA the following with the exception of______.
选项
A、relief
B、fatigue
C、excitement
D、pleasure
答案
B
解析
由第四段和第五段可知,火星上有水这一事实让科学家们激动不已,快乐无比,也让科学家们松了一口气,所以排除选项A、C和D,故B为正确答案。
转载请注明原文地址:https://kaotiyun.com/show/bgbK777K
0
专业英语八级
相关试题推荐
A、Theadvantagesoflivinginvacationrentals.B、Theadvantagesoflivinginhotels.C、Theaccommodationconditionduringatri
ReadingTipsI.Three【T1】______phasesofreading【T1】______—beforereading—duringreading—afterreadingⅡ.Pre-readingt
ReadingTipsI.Three【T1】______phasesofreading【T1】______—beforereading—duringreading—afterreadingⅡ.Pre-readingt
ReadingTipsI.Three【T1】______phasesofreading【T1】______—beforereading—duringreading—afterreadingⅡ.Pre-readingt
ReadingTipsI.Three【T1】______phasesofreading【T1】______—beforereading—duringreading—afterreadingⅡ.Pre-readingt
ChineseAmericansI.EarlyimmigrationA.thefirstgroupofChineseimmigrants—cameto【T1】______【T1】______—becamethe【T2】__
ChineseAmericansI.EarlyimmigrationA.thefirstgroupofChineseimmigrants—cameto【T1】______【T1】______—becamethe【T2】__
PASSAGEONEWhydoestheauthormentionthemonumentinBostoninPara.5?
随机试题
组织
目前认为关于肺气肿发生的机理,下列哪项不正确
以TPP为辅助因子的酶是
【背景资料】某公司中标承建中压A燃气管线工程,管道直径DN30mm,长26km,合同价3600万元。管道沟槽开挖过程中,遇到地质勘查时未探明的废弃砖沟,经现场监理工程师口头同意,施工项目部组织人员、机具及时清除了砖沟,进行换填级配砂石处理,使工程
出口危险货物包装检验包括性能检验和使用鉴定。( )
开设跨学科课程或建立跨学科专业体现了高等教育课程发展的()。
InancientEgypt(古埃及),peoplebelievedthatthecatwasagod.Whena【C1】______dieditsownersshowedtheirsadnessbythestra
设f(χ)在[0,1]上连续,在(0,1)内可导,f(0)=0,f()=1,f(1)=0.证明:(1)存在η∈(,1),使得f(η)-η;(2)对任意的k∈(-∞,+∞),存在ξ∈(0,η),使得f′(ξ)-k[f(ξ)-ξ]=1.
某高校为了使学生更好地进行职场定位和职业准备,提高就业能力,该校学工处将于2013年4月29日(星期五)19:30-21:30在校国际会议中心举办题为“领慧讲堂一一大学生人生规划”就业讲座,特别邀请资深媒体人、著名艺术评论家赵蕈先生担任演讲嘉宾。请根据上述
Isthat______newcar?
最新回复
(
0
)