火星甲烷之谜：它意味着有生命存在吗？

赖丽霞

NASA是美國联邦政府的一个政府机构，负责美国的太空计划。最近，该机构称其在火星上发现甲烷的踪迹，这是否表明火星上已经有生命存在呢？让我们一起来看看吧！

难词探意

1. methane /?meθe?n/ n. 甲烷

2. device /d??va?s/ n. 装置

3. geological /?d?i???l?d??kl/ adj. 地质（学）的

4. microbial /ma??kr??b??l/ adj. 微生物的

The United States space agency， NASA， said its Mars exploration vehicle recently recorded a high level of methane gas on the planet. The discovery is exciting because the presence of methane gas could support the case for life on Mars.

NASAs Curiosity vehicle recently recorded the largest level of methane ever measured during its seven?year Mars mission. Methane has no color or smell. A special instrument on Curiositys 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 carbon dioxide. Nearly all the methane gas found in Earths atmosphere is produced by biological activity. It usually comes from animal and plant life. But it can also be formed by geological processes， such as interactions between rocks and water.

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 Curiositys other activities to investigate further. “Its exciting because microbial life is an important source of methane on Earth，” NASA said in a statement announcing the discovery.

However， Curiositys 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，” NASA said. 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，” said Ashwin Vasavada， Curiositys project scientist at NASAs Jet Propulsion Laboratory in Pasadena， California. “Were more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere.”

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 theyre located on Mars，” NASA said. Scientists hope this understanding will come as Curiosity continues to collect methane data in its search for possible life.

[Reading][Check]

1. What does the underlined word “discovery” refer to in paragraph 1？ （no more than 7 words）

2. What can the laser spectrometer do？ （no more than 20 words）

3. What is methane in Earths atmosphere mainly produced by？ （no more than 10 words）

4. Was it the first time Curiosity has found methane gas in the Martian atmosphere？（no more than 5 words）

5. Whats Ashwin Vasavada？ （no more than 5 words）

[Language][Study]

Difficult sentence

One leading theory is that methane is being released from underground areas created by possible life forms that disappeared long ago.

【翻譯】

【点石成金】第一个that引导表语从句，表语从句中主语为methane，第二个that引导定语从句，先行词为life forms。