VOA慢速英语2021--研究称闪电可能有助于地球上生命的发展

Study: Lightning May Have Helped Life Develop on Earth

A new study suggests lightning strikes that hit Earth after its formation may have unlocked a necessary chemical element to support the beginning of life.

Researchers say the lightning may have supplied enough phosphorus to Earth during the first billion years after the planet was formed. Scientists believe life started on Earth about 3.5 to 4.5 billion years ago.

Phosphorus is an important element for the formation of life. It helps form cell structures and supports DNA¹, the material present in nearly all living organisms. But on early Earth, phosphorus is believed to have been locked inside minerals that cannot dissolve in water.

Until now, it was widely believed that meteorites³ that struck Earth were mainly responsible for the presence of "bioavailable" phosphorus. Some meteorites contain a phosphorus mineral called schreibersite, a highly reactive mineral that can form organic molecules⁴.

But when lightning strikes the ground, it can create glassy rocks called fulgurites by super-heating and sometimes vaporizing rocks on the surface. This process frees the phosphorus locked inside. As a result, these fulgurites can contain schreibersite, which is soluble⁵ in water, where life is thought to have formed.

Researchers in the United States and Britain estimated that early Earth saw 1 to 5 billion lightning strikes hit Earth each year - compared to about 560 million yearly today. That would add up to 1 quintillion strikes after a billion years, forming at least 1 billion fulgurites.

A study describing the research results recently appeared in the publication Nature Communications.

The researchers said phosphorus minerals caused by lightning strikes were found to have been higher by about 3.5 billion years ago. This is about the age of the earliest-known fossils widely accepted to be those of microorganisms, the researchers found.

"Lightning strikes, therefore, may have been a significant part of the emergence⁶ of life on Earth," said Benjamin Hess, a Yale University graduate student in earth and planetary sciences. He was the lead writer of the study.

Hess told Reuters news agency that unlike meteorite² hits that generally decrease over time, lightning strikes can happen continuously over a planet's history. He added that this means lightning strikes may also be a very important element for providing the phosphorus needed for the emergence of life on other Earth-like planets.

The researchers also examined an unusually large fulgurite formed when lightning struck near a home outside Chicago, Illinois in 2016. "Our research shows that the production of bioavailable phosphorus by lightning strikes may have been underestimated," study co-writer Jason Harvey told Reuters. He is a professor of geochemistry at Britain's University of Leeds.

Among the materials considered necessary for life are water, carbon, hydrogen, nitrogen, oxygen, sulfur⁷ and phosphorus, along with an energy source.

Scientists believe the earliest bacteria-like organisms were formed in Earth's early waters. But there is a debate over when this happened and whether it happened in warm and shallow waters or in deeper waters.

Hess said that new research does not completely cancel the theory that meteorites could have been another source of life-giving phosphorus.

"Meteor impacts around the time of the emergence of life are far less than thought a decade ago," Hess said. "But I don't see our work as a competition against meteorites as a source of phosphorus. The more sources, the better," he added.

Words in This Story

dissolve – v. to turn from a solid into a liquid

meteorite – n. a piece of rock or metal that has fallen to the ground from outer space: a meteor that reaches the surface of the Earth without burning up entirely⁸

quintillion – n. a number equal to 1 followed by 18 zeros

fossil – v. part of an animal or plant from thousands of year ago, preserved in rock

emerge – v. to appear from somewhere

source – n. something that provides what is wanted or needed

shallow – adj. not deep

impact – n. an act or event in which something strikes another thing

decade – n. a period of 10 years

1 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

2 meteorite   

n.陨石；流星

参考例句：

• The meteorite in Jilin Exhibition Hall is believed to be the largest in the world.吉林展览馆的陨石被认为是世界上最大的。
• The famous Murchison meteorite smashed into the Australian ground in 1969.1969年著名的默奇森陨石轰然坠落在澳大利亚。

3 meteorites   

n.陨星( meteorite的名词复数 )

参考例句：

• Small meteorites have left impact craters all over the planet's surface. 这个行星的表面布满了小块陨石留下的撞击坑。 来自《简明英汉词典》
• One theory about the existence of extraterrestrial life rests on the presence of carbon compounds in meteorites. 地球外存在生命的理论是基于陨星上存在碳化合物质这一事实的。 来自《简明英汉词典》

4 molecules   

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。

5 soluble   

adj.可溶的；可以解决的

参考例句：

• These tablets are soluble in water.这些药片可在水中溶解。
• Camphor is soluble in alcohol.樟脑在酒精中可以溶化。

6 emergence   

n.浮现，显现，出现，（植物）突出体

参考例句：

• The last decade saw the emergence of a dynamic economy.最近10年见证了经济增长的姿态。
• Language emerges and develops with the emergence and development of society.语言是随着社会的产生而产生，随着社会的发展而发展的。

7 sulfur   

n.硫，硫磺（=sulphur）

参考例句：

• Sulfur emissions from steel mills become acid rain.炼钢厂排放出的硫形成了酸雨。
• Burning may produce sulfur oxides.燃烧可能会产生硫氧化物。

8 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。