Ironically, it was the ambitious reach of NASA's Viking spacecraft that set back the exploration of Mars for so many years. As proffered by such enthusiastic visionaries as Carl Sagan, the question that Viking would answer seemed not to be whether Mars was home to life but to what kind. Would it be bacteria? Algae? Lichen? Or other, more complex forms? The two landers carried suites of astrobiological life detection apparatuses that were marvels to behold: tiny growing chambers packed with nutrients to awaken ancient Martian spores, radioactive tracers to identify the metabolic activities of microbes, and chemical analysis systems to identify the expected respiratory byproducts.
Alas, save for some narrowly held dissenting opinions, no interpretation of the data supported the existence of viable life forms on Mars. Instead, the probes found an atmosphere so harshly oxidizing that biotic matter, as then understood, could scarcely survive. And so, like a rebuffed suitor retreating across the room to collect his composure, the American exploration of space was left hunting for new directions to explore. Mars was dead.
But time heals all shame and the allure of the red planet could not long remain at bay. It took a series of events to bring Martian exploration back into the limelight. The discovery of extremophiles, forms of life here on Earth that existed in conditions previously considered completely inhospitable to any biological process, combined with a new understanding of the limitations of Viking's sensors (which, it turned out, had been somewhat oversold in an effort to secure backing for the missions) to awaken the possibility that life could still exist on Mars, albeit perhaps in forms we would scarcely recognize. The competitive spirit of the Reagan presidency then provided the necessary political will to return to Mars, for the Russians had suffered no shame from the American frustration and were then pursuing an ambitious program of Martian exploration.
These factors combined to bring about the launch of Mars Observer, a mission almost as grandiose as Viking had been. Technical shortsightedness caused the Mars Observer craft to explode while preparing to enter orbit around Mars. But by then the spirit was relit and a sequence of missions, some humble and some ambitious, some successful and some not, flew throughout the late 1990's and into the new millennium. Today's goals are less dramatic. No surefire detection of life is promised or looked for. Instead, a methodical tracing of the biologic, climatologic, and geologic history of Mars is slowly expanding our understanding of our close planetary neighbor. This systematic exploration may even one day progress to a reexamination of the great question that has haunted man's imagination for centuries: Is there life on Mars?
1 : Based on the information in the passage, which of the following best characterizes the results of the Viking missions?
a) A methodical understanding of the biologic, climatologic, and geologic history of Mars.
b) Undisputed proof that no life could possibly exist on Mars.
c) Widely disputed and inconclusive results regarding the biological potential of Mars.
d) A general belief that life, as then recognized, was unlikely to exist on Mars.
e) Widespread enthusiasm towards continued Martian exploration.
2: The passage discusses which of the following as a reason why the Viking landers failed to detect signs of life on Mars?
a) Their life detection apparatus was not designed to detect traces of the sort of life now believed to exist on Mars.
b) Subsequent investigations proved that there was no life present for them to detect.
c) The Viking landers only surveyed two small areas of the planet and might have missed locations more favorable to biological activity.
d) The instruments were not as sensitive as originally claimed and, if life on Mars does exist, it may do so in a form they would not have correctly identified.
e) The Viking landers could only identify complex forms of life such as bacteria and algae.
3 : Which of the following would most effectively and accurately title this article?
a) Viking and Mars Observer - Two Studies in Hubris
b) Back to the Red Planet, One Step at a Time
c) Beat the Russians!
d) Astrobiological Possibilities of Martian Extremophiles
e) Moving On - Why Space Exploration Must Abandon a Dead Mars
4. According to the passage, the competitive spirit of the Reagan presidency played what role in the exploration of Mars?
a) It provided political impetus to move forward with the launch of the Viking Landers.
b) It ensured the flight of a sequence of missions from the late 1990's through the new millennium.
c) It led to the opposition of Russian efforts to explore Mars.
d) It was like a rebuffed suitor retreating across the room.
e) It contributed to the launch of the Mars Observer mission.
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发表于 2021-10-13 17:03:13
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