Question

    NASA’s Curiosity vehicle recently recorded the largest level of methane(甲烷) ever measured during its seven-year Mars mission. The discovery is exciting because the existence of methane gas could support the case for life on Mars.

Methane has no color or smell. A special instrument on Curiosity’s Mars Science Laboratory recorded the increased gas level. The device, called a laser spectrometer, measures levels of chemical elements and gases in the Martian atmosphere. In addition to methane, the instrument can record levels of water and CO2. Nearly all the methane gas found in Earth’s atmosphere is produced by biological activity. It usually comes from animal and plant life. But it can also be formed by geological(地质的) processes, such as interactions between rocks and water. NASA said the increased methane was measured to be about 21 parts per billion by volume (ppbv). One ppbv means that if you take a volume of air on Mars, one billionth of the volume of air is methane.

It was not the first time Curiosity has found methane gas in the Martian atmosphere. About a year ago, NASA announced that Curiosity had discovered sharp seasonal increases in the gas. This time, NASA said the measured methane gas level was clearly larger than any others observed in the past. NASA officials even temporarily stopped Curiosity’s other activities to investigate further.

“It’s exciting because microbial(微生物的) life is an important source of methane on Earth,” NASA said in a statement announcing the discovery. However, Curiosity’s team carried out a follow-up methane experiment that showed a sharp drop in levels of the gas. The second examination found the level was less than one part per billion by volume. That number was close to the background levels Curiosity sees all the time. The rise and fall of the methane gas levels left NASA scientists with more questions than answers. The scientists are continuing to study possible causes for the sudden increase. The methane mystery continues.

Curiosity does not have instruments that can exactly identify whether the source of the methane is biological or geological. One leading theory is that methane is being released from underground areas created by possible life forms that disappeared long ago. Even though Mars has no active volcanoes, scientists believe it is also possible that methane is being produced by reactions involving carbon materials and water.

A clearer understanding of methane levels over time could help scientists determine where they’re located on Mars. Scientists hope this understanding will come as Curiosity continues to collect methane data in its search for possible life.

1.Curiosity discovered.

A.the largest methane gas level ever observed on Mars

B.the existence of life on Mars

C.the reason for the increased methane

D.interactions between rocks and water

2.Why did NASA officials once stop Curiosity’s other activities?

A.To further examine the methane gas level on Mars.

B.To seek possible life existing on Mars.

C.To check the quality of Curiosity’s mission.

D.To find seasonal increases in the methane gas.

3.What can we learn from the last three paragraphs?

A.Causes for the change of methane have been proved by Curiosity.

B.Curiosity has proved the location of methane by instruments.

C.Scientists think reactions involving carbon materials and water may produce methane.

D.Identifying the source of methane has helped scientists search for possible life on Mars.

4.The passage is probably taken from .

A.a geography textbook B.a science newspaper

C.a health magazine D.a travel brochure

Answer

1.A

2.A

3.C

4.B

【解析】

本文是一篇科学类新闻报道，文中报道了好奇号在火星上探测到有记录以来大气中的最高甲烷含量，并由此引发火星上是否存在或曾经存在生命的一系列讨论和更进一步科学探索的新闻。

1.细节理解题。根据原文第一段“NASA’s Curiosity vehicle recently recorded the largest level of methane ever measured during its seven-year Mars mission.”及原文第三段“This time, NASA said the measured methane gas level was clearly larger than any others observed in the past.”可知此次探测到的火星大气甲烷含量是有观测历史以来最高的，A项与原文表述契合，故选A。

2.细节理解题。根据第三段内容，一年前好奇号就曾探测到火星大气甲烷含量的季节性剧烈升高，而这次则直接探测到有记录以来的最高含量，并结合该段最后一句“NASA officials even temporarily stopped Curiosity’s other activities to investigate further.”可知，暂时停止其它工作，是为了集中精力更深入地检查、探测、研究火星大气中的甲烷含量，A符合题意；本题干扰项为D，根据文章内容，甲烷含量季节性升高的发现，已经是一年前的成果和事实了，故应排除该选项。综上所述，故选A。

3.细节理解题。根据第五段内容“Even though Mars has no active volcanoes, scientists believe it is also possible that methane is being produced by reactions involving carbon materials and water.”可知，即使火星上没有活跃的火山，但甲烷也可能由碳材料与水反应产生，C符合题意；甲烷含量改变的原因、甲烷产生并释放的位置都还是一个谜团，A、B选项应排除；本题D为干扰项，根据原文“Curiosity does not have instruments that can exactly identify whether the source of the methane is biological or geological.”可知好奇号上根本没有能够准确辨认出甲烷是生物来源还是地质来源的仪器，故以此帮助了科学家寻找火星上可能存在的生命更不可能，D应予排除。综上所述，故选C。

4.推理判断题。本题要求分析文章的可能出处，本文是一篇新闻，报道了好奇号在火星上探测到有记录以来大气中的最高甲烷含量这一新闻，并进行了拓展讨论。因此本文属于科学、天文范畴，且具有前沿性，不可能来源于健康杂志或旅游指南，排除C、D选项；教科书一般没有在第一时间紧跟前沿、刊登实时新闻的条件，且地理教科书一般讲解的是地球情况，排除A选项。本文来自科学科技类报纸最为合理，故选B。