VOA科学技术2024--Study: Moon's Thin Atmosphere Likely Formed by Meteorite Strikes

Scientists say new examinations of soil collected on the moon suggest its atmosphere might have been created by repeated meteorite¹ strikes.

Researchers studying the moon first used instruments to confirm it had an atmosphere in the early 1970s. The American space agency NASA explains the moon's atmosphere is "very thin and weak." It is technically² considered an "exosphere."

The newly examined soil was collected by NASA astronauts during America's Apollo program from 1969 to 1972. The trips resulted in astronauts capturing about 382 kilograms of rocks and soil, called samples.

Instead of attempting to measure the moon's atmosphere in a direct way, investigators³ looked to the old soil material. They theorized that the soil should contain residue⁴ material from atoms released into the lunar atmosphere over billions of years.

The research was led by scientists at the University of Chicago and Massachusetts Institute of Technology (MIT). Their results recently appeared in a study in the publication Science Advances. Nicole Nie was the lead writer of the study. She is a planetary scientist at MIT.

Meteorite impacts

Nie said that when meteorites⁵ impact, or hit, an object like the moon, they create very high temperatures. Such strikes can heat up the surface by 2,000 to 6,000 degrees Celsius⁶. These extreme temperatures melt and vaporize rocks at the surface and release atoms contained in dust and soil into the atmosphere.

Some of the atoms end up being pushed into space, while others remain just above the surface. The researchers said the soil examinations led to the discovery that the moon's atmosphere was formed through a process known as "impact vaporization."

Nie and her team centered their examinations on two main elements - potassium and rubidium. These substances were chosen because they can easily be vaporized by meteorite hits. The process involved studying the behaviors of different kinds of isotopes⁷ found in potassium and rubidium. That study persuaded the team that repeated meteorite strikes formed the atmosphere.

In the past, studies have shown the moon's atmosphere might have been created by either meteor activity or the solar wind. Solar wind describes a continuous flow of charged particles from the sun that spreads across the solar system.

The researchers said the latest study provides new evidence that most of the lunar atmosphere was likely formed by repeated meteorite hits over billions of years. After testing 10 samples of lunar soil, the team concluded that much more of the atmosphere is due to meteor activity than to the solar wind.

"At least 70 percent of the lunar atmosphere is created by these meteorite impacts," Nie said in a statement. "A much smaller percentage is created by the solar wind abrasion⁸ of the surface," she added.

Nicolas Dauphas is a professor of geophysical sciences at the University of Chicago. He helped lead the research. Dauphas said, "It turns out the answer to this longstanding question was right in front of us - preserved in lunar soil brought back to Earth by the Apollo missions."

Nie said understanding such processes can be extremely valuable to planning future missions to the moon, Mars and beyond. "If humans want to move to different planetary bodies someday, we will have to understand what's going on at the surface to be able to prepare." She added, "Each planetary body is different, and the more we understand about these processes, the more complete picture we'll have."

Words in This Story

meteorite - n. a piece of rock from outer space that has fallen to a planet's surface

exosphere - n. the outermost⁹ layer of a planet's atmosphere

residue - n. something that remains¹⁰ after most of a substance has disappeared or been removed

vaporize - v. to turn, or cause something to turn, from a solid or liquid state into a gas

abrasion - n. the process of rubbing away the surface of something

preserve - v. to keep something the same or prevent it from being damaged or destroyed

1 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。

2 technically   

adv.专门地，技术上地

参考例句：

• Technically it is the most advanced equipment ever.从技术上说，这是最先进的设备。
• The tomato is technically a fruit,although it is eaten as a vegetable.严格地说，西红柿是一种水果，尽管它是当作蔬菜吃的。

3 investigators   

n.调查者，审查者( investigator的名词复数 )

参考例句：

• This memo could be the smoking gun that investigators have been looking for. 这份备忘录可能是调查人员一直在寻找的证据。
• The team consisted of six investigators and two secretaries. 这个团队由六个调查人员和两个秘书组成。 来自《简明英汉词典》

4 residue   

n.残余，剩余，残渣

参考例句：

• Mary scraped the residue of food from the plates before putting them under water.玛丽在把盘子放入水之前先刮去上面的食物残渣。
• Pesticide persistence beyond the critical period for control leads to residue problems.农药一旦超过控制的临界期，就会导致残留问题。

5 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》

6 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

7 isotopes   

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》

8 abrasion   

n.磨（擦）破，表面磨损

参考例句：

• Diamonds have extreme resistance to abrasion.钻石极抗磨损。
• This analysis is helpful to the research of derailment and abrasion machenism.该分析有助于脱轨和磨耗机理的探讨。

9 outermost   

adj.最外面的，远离中心的

参考例句：

• He fired and hit the outermost ring of the target.他开枪射中了靶子的最外一环。
• The outermost electron is shielded from the nucleus.原子核对最外层电子的作用受到屏蔽。

10 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。