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 Appolo astronauts rocketed to the moon in a dramatic show of 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 as humanitys next great terra incognita. 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 planets 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 mctcorite 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.

　　36.According to the passage, the chief purpose of explorers in going to unknown places in the past was .

　　A) to display their countrys military might C) to find new areas for colonization

　　B) to accomplish some significant science D) to pursue commercial and state interests

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

　　A) international cooperation C) scientific research

　　B) nationalistic reasons D) long-term profits

　　38. 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.

　　39. By saying With Mars the scientific stakes are arguably higher than they have ever been , 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

　　40. 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 travelled to Earth on a meteorite

　　C) reveal the kind of conditions under which life originates

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

　　36.D 37.C 38.A 39.B 40.C

　　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 Appolo astronauts rocketed to the moon in a dramatic show of 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 as humanitys next great terra incognita. 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 planets 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 mctcorite 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.

　　36.According to the passage, the chief purpose of explorers in going to unknown places in the past was .

　　A) to display their countrys military might C) to find new areas for colonization

　　B) to accomplish some significant science D) to pursue commercial and state interests

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

　　A) international cooperation C) scientific research

　　B) nationalistic reasons D) long-term profits

　　38. 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.

　　39. By saying With Mars the scientific stakes are arguably higher than they have ever been , 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

　　40. 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 travelled to Earth on a meteorite

　　C) reveal the kind of conditions under which life originates

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

　　36.D 37.C 38.A 39.B 40.C