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VOA科学技术2022--据研究火星岩石含有可能与生命有关的碳“信号”

时间：2022-02-20 23:23:53

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Study: Mars Rock Contains Carbon ‘Signals’ Possibly Linked to Life

A new study has found that rock material collected on Mars contains the same kinds of carbon "signals" linked to living organisms on Earth.

Scientists say the presence of carbon may suggest evidence of ancient biological life on Mars. But they also note that the finding could be related to nonbiological processes.

The study is based on rock samples collected by the American space agency NASA's Curiosity explorer. The explorer, or rover, landed on Mars in 2012. It has been exploring areas around the planet's Gale1 Crater2.

The rover used a robotic arm to collect rock material from below the surface of Mars. The samples were subjected to high heat inside a chemistry laboratory on Curiosity, NASA explained. This resulted in a release of gas from the rock material.

One of the rover's instruments then measured isotopes4 from carbon released during the heating process. Results of the experiment were examined by scientists on Earth. Their findings were recently reported in a study in Proceedings5 of the National Academy of Sciences (PNAS).

Carbon is an important element because it is present in all life on Earth. Carbon has two naturally occurring isotopes, 12 and 13. Measuring these isotopes can provide researchers with signals about carbon-related activities from the past.

The study found that the collected samples had large amounts of carbon 12. This kind of carbon is used by living creatures on Earth to get energy from food or the sun, NASA noted6.

Christopher House is a Curiosity scientist based at Pennsylvania State University. He led the study.

House said in a statement that on Earth, "processes that would produce the carbon signal we're detecting on Mars are biological." He added: "We have to understand whether the same explanation works for Mars, or if there are other explanations, because Mars is very different."

The biological explanation involves the idea that bacteria may have released methane7 gas into the atmosphere. Ultraviolet light could have converted this gas into larger, more complex molecules8 that settled on the surface. These molecules could have remained in the Martian rocks collected by Curiosity.

In 2019, NASA researchers reported that Curiosity had measured levels of methane on the surface of Mars. While the team said this could also be a sign of ancient life, NASA has not been able to confirm whether the methane resulted from biological causes.

Two other theories – both nonbiological – are identified in the new study.

One explanation suggests the carbon signals might have resulted from an interaction of ultraviolet light and carbon dioxide gas in the Martian atmosphere. This process could have produced carbon-containing molecules that settled on the surface.

The other theory is that the carbon could have resulted from an event hundreds of millions of years ago. In that event, the solar system passed through a huge cloud of dust that could have been rich in the kind of carbon discovered in the rock samples.

"All three explanations fit the data," House said. "We simply need more data to rule them in or out.

Andrew Steele is a Curiosity scientist based at the Carnegie Institution for Science in Washington D.C. He noted that Curiosity is the first rover to be equipped with the tools to study carbon isotopes on the surface of Mars.

"Defining the carbon cycle on Mars is absolutely key to trying to understand how life could fit into that cycle," Steele said. "We have done that really successfully on Earth, but we are just beginning to define that cycle for Mars," he added.

Words in This Story

sample – n. a small amount of something that gives you information about the thing it was taken from

isotope3 – n. a form of atom that has a different atomic weight from other forms of the same atom but the same chemical structure

occur – v. to happen

convert – v. to change the appearance, form or purpose of something

cycle – n. a series of events that happen in a particular order and are often repeated

absolutely – adv. completely

key – adj. very important in influencing or achieving something


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1 gale Xf3zD     
n.大风，强风，一阵闹声（尤指笑声等）
参考例句：
  • We got our roof blown off in the gale last night.昨夜的大风把我们的房顶给掀掉了。
  • According to the weather forecast,there will be a gale tomorrow.据气象台预报，明天有大风。
2 crater WofzH     
n.火山口，弹坑
参考例句：
  • With a telescope you can see the huge crater of Ve-suvius.用望远镜你能看到巨大的维苏威火山口。
  • They came to the lip of a dead crater.他们来到了一个死火山口。
3 isotope isotope     
n.同位素
参考例句：
  • The isotope ratio is directly used for comparing oils or gases.同位素比率直接用于比较各种石油或天然气。
  • How to apply a radio isotope?如何运用放射性同位素？
4 isotopes 92848c3160703e48dc3b552ac6f54115     
n.同位素；同位素( isotope的名词复数 )
参考例句：
  • the many isotopes of carbon 碳的诸多同位素
  • Tritium is one of the mildest radioactive isotopes. 氚是最和缓的放射性同位素之一。 来自《简明英汉词典》
5 proceedings Wk2zvX     
n.进程，过程，议程；诉讼(程序)；公报
参考例句：
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
6 noted 5n4zXc     
adj.著名的，知名的
参考例句：
  • The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
  • Jim is noted for arriving late for work.吉姆上班迟到出了名。
7 methane t1Eyx     
n.甲烷，沼气
参考例句：
  • The blast was caused by pockets of methane gas that ignited.爆炸是由数袋甲烷气体着火引起的。
  • Methane may have extraterrestrial significance.甲烷具有星际意义。
8 molecules 187c25e49d45ad10b2f266c1fa7a8d49     
分子( molecule的名词复数 )
参考例句：
  • The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
  • Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

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