VOA慢速英语--研究称月球上崎岖不平的地区可能会广泛形成水冰

Study: Rough Areas on Moon May Permit Water Ice to Widely Form

A new study suggests that rough areas on the moon's surface block sunlight and permit water ice to form across wide areas.

The U.S. space agency NASA already confirmed last year that results from two studies suggested water ice likely existed across much of the moon's surface, even during daytime.

One of those studies centered on so-called "cold traps" observed on the moon that hold frozen water. These areas exist in a state of permanent darkness because temperatures are below about minus 160 degrees Celsius¹.

Until now, scientists have not been sure what was permitting these traps to exist. Especially since the moon does not have a thick atmosphere to help water survive. One theory was that water molecules³ could be trapped on the lunar surface inside rock or other material that resulted from meteorite⁴ strikes.

But a new study by NASA researchers provides another possible explanation for how water ice could remain in many areas of the moon's surface. It presents evidence that the rough, rocky surface creates shadows that permit water ice to survive.

The researchers note that past observations suggested there were movements of water through the lunar day. A lunar day is the time it takes for one point on the Earth to make one complete rotation⁵ and end up at the same point in relation to the moon.

Studies have provided evidence that the amount of water decreased on the moon's surface when sunlight was brightest and increased with less sunlight.

The latest study was led by Björn Davidsson, a scientist at NASA's Jet Propulsion Laboratory (JPL) in California. He teamed up with another JPL researcher, Sona Hosseini, to carry out the research.

The team revised past computer modeling to include rough surface areas of the moon that can be seen in images collected from NASA's Apollo missions from 1969 to 1972. The research results recently appeared in the publication Monthly Notices of the Royal Astronomical⁶ Society.

The study suggests that as surface frost that forms in cold areas receives sunlight, it can then be "cycled into the moon's exosphere." The exosphere is the thin, outer area that forms around a planet or satellite object, such as the moon.

"Frost is far more mobile than trapped water," Davidsson said in a statement. "Therefore, this model provides a new mechanism⁷ that explains how water moves between the lunar surface and the thin lunar atmosphere."

The researchers say their study is the first to examine how shadows on the lunar surface can affect the ability of water molecules to survive as frost during the daytime.

They noted⁸ that such research is important to help scientists better understand how water enters and leaves the moon's exosphere.

Hosseini said understanding water as a resource is "essential" for future NASA missions or any possible private space exploration. She added if water ice is available in sunlit areas of the moon, future explorers could use it for fuel and drinking water.

"But first, we need to figure out how the exosphere and surface interact and what role that plays in the cycle," Hosseini said.

The researchers say they plan to test their theory by leading a team to develop small sensors⁹ to measure signals given off by a molecule² contained in water ice. The sensing device will be designed to be used on small landers or robotic explorers that could be sent to the moon in future missions.

Words in This Story

shadow – n. a dark shape that appears on a surface when someone or something moves between the surface and a source of light

revise – v. change something that has already been worked on

mission – n. a flight by an aircraft or spacecraft to perform a specific task

frost – n. a thin layer of ice that forms on surfaces, especially at night when it is cold

mobile – adj. able to move or be moved easily

mechanism – n. a part of a piece of equipment that does a particular job

essential – adj. very important and necessary

figure out – v. to understand or find something, such as a reason or a solution by thinking

1 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。

2 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

3 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。

4 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。

5 rotation   

n.旋转；循环，轮流

参考例句：

• Crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
• The workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。

6 astronomical   

adj.天文学的，（数字）极大的

参考例句：

• He was an expert on ancient Chinese astronomical literature.他是研究中国古代天文学文献的专家。
• Houses in the village are selling for astronomical prices.乡村的房价正在飙升。

7 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

8 noted   

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。

9 sensors   

n.传感器，灵敏元件( sensor的名词复数 )

参考例句：

• There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
• Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时，有很大变化。 来自辞典例句