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For centuries, explorers have risked their lives venturing into the unknown for reasons that were to varying degrees economic and nationalistic. Columbus went west to look for better trade routes to the Orient and to promote the greater glory of Spain. Lewis and Clark journeyed into the American wilderness to find out what the U.S. had acquired when it purchased Louisiana, and the Apollo astronauts rocketed to the moon in a dramatic show off technological muscle during the cold war.

Although their missions blended commercial and political-military imperatives, the explorers involved all accomplished some significant science simply by going where no scientists had gone before.

Today Mars looms（隐约出现）as humanity's next great terra incognita（未探明之地）. And with doubtful prospects for a short-term financial return, with the cold war a rapidly fading memory and amid a growing emphasis on international cooperation in large space ventures, it is clear that imperatives other than profits or nationalism will have to compel human beings to leave their tracks on the planet's reddish surface. Could it be that science, which has long played a minor role in exploration, is at last destined to take a leading role? The question naturally invites a couple of others: are there experiments that only humans could do on Mars? Could those experiments provide insights profound enough to justify the expense of sending people across interplanetary space?

With Mars the scientific stakes are arguably higher than they have ever been. The issue of whether life ever existed on the planet, and whether it persists to this day, has been highlighted by mounting evidence that the Red Planet once had abundant stable, liquid water and by the continuing controversy over suggestions that bacterial fossils rode to Earth on a meteorite（陨石）from Mars. A more conclusive answer about life on Mars, past or present, would give researchers invaluable data about the range of conditions under which a planet can generate the complex chemistry that leads to life. If it could be established that life arose independently on Mars and Earth, the finding would provide the first concrete clues in one of the deepest mysteries in all of science: the prevalence of life in the universe.

1.According to the passage, the chief purpose of explorers in going to unknown places in the past was______.

A.to display their country's military might　B.to accomplish some significant science

C.to find new areas for colonization　　　D.to pursue commercial and state interests

2.At present, a probable inducement for countries to initiate large-scale space ventures is______.

A.international cooperation　B.nationalistic reasons

C.scientific research　　　D.long-term profits

3.What is the main goal of sending human missions to Mars?

A.To find out if life ever existed there.

B.To see if humans could survive there.

C.To prove the feasibility of large-scale space ventures.

D.To show the leading role of science in space exploration.

4.By saying "With Mars the scientific stakes are arguably higher than they have ever been" (Line 1, Para. 4), the author means that______.

A.with Mars the risks involved are much greater than any previous space ventures

B.in the case of Mars, the rewards of scientific exploration can be very high

C.in the case of Mars, much more research funds are needed than ever before

D.with Mars, scientists argue, the fundamental interests of science are at issue

5.The passage tells us that proof of life on Mars would______.

A.make clear the complex chemistry in the development of life

B.confirm the suggestion that bacterial fossils traveled to Earth on a meteor

C.reveal the kind of conditions under which life originates

D.provide an explanation why life is common in the universe

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1.【答案】D。

【解析】细节题。选择依据为文章第一句话。该句中的reasons即问题所问的purpose。依据第二段前半句话也可知答案为D。该句中的imperative（n. & a.　必要的，紧急的，极重要的；命令的）与问题中的purpose对应。A项（显示军威）、C项（寻找新的殖民地）都只是经济和政治因素的一种，探险所肩负的经济、政治使命不一定就是显示军威或寻求新殖民地，所以可排除A、C项，可从第二段第一句话中看出：过去的探险虽然大都具有一定科学意义，但这只是探险活动的客观结果，而非探险的主观目的。

2.【答案】C。

【解析】推断题。回答依据为第三段第二、第三句话，尤其是第二句话。B、D两项都容易被排除，A项迷惑性较大。原文意思是：在短期内看不到经济效益、冷战结束、太空探索中日益强调国际合作的今天，显然促使人类踏上火星的原因不是利润和民族主义。

3.【答案】A。

【解析】细节题。选择依据为第四段第二句。文章中找不到B、C两项的意思。至于D项，科学目的在太空探索中具有重要意义，是其主要目的，但人类登陆火星并不是为了显示科学在太空探索中的重要意义。

4.【答案】D。

【解析】推断题。文章中找不到A、B、C三项的意思。要正确理解这句话的意思，必须联系上下文。上文中说：以前的探险主要是为着经济和民族主义原因，但火星探险却在近期内看不到经济效益，而且现在冷战结束、在太空探索中强调国际合作，那么，科学目的是否会在火星探索中占据主导地位呢？在火星探索中，科学家们比以往哪次探险都更积极地参与其中。由此可见，该句的意思是说：在火星探险中，科学家更多地参与其中是因为科学研究是探险的主要目的。D项与此意思相同。

5.【答案】D。

【解析】细节题。选择依据为文章最后一句话。文章中找不到A项的意思；B项的出题依据为第四段第二句话后半部分内容，但仔细阅读该句便可知B项内容与其不符；C项具有一定迷惑性，其出题依据是倒数第二句话。该句谓语部分（包括宾语）与C项意思类似，但主语的含义与题干中宾语从句的主语（proof of live on Mars）含义不同。