VOA慢速英语--研究称冰云可能允许火星上有流动的水

A new study suggests icy clouds above early Mars¹ could have provided² the warmth to permit flowing water on the Red Planet³.

American researchers used a computer model to predict that icy clouds in the Mars atmosphere may have created a greenhouse⁴ effect. Earth also experiences a greenhouse effect, which happens when gases in the atmosphere trap in heat from the sun.

Today, Mars enjoys a cold, desert climate. Any existing water is believed to be in the form of ice because of the planet's extremely cold temperatures. There is, however, a rich amount of evidence suggesting that rivers, lakes and even oceans once existed on Mars.

In fact, scientists announced in February they had created a new map designed to identify the best sources of water ice on Mars.

Scientists have long sought to explain what made it possible for Mars to have the large rivers and lakes they believe existed in the planet's ancient past.

Researchers involved in the latest study were interested in coming up with a possible explanation. They created a three-dimensional, or 3D, model of the Martian atmosphere.

The study was led by Edwin Kite, a professor and planetary scientist at the University of Chicago. He said the research resulted in a major discovery – that ice on the surface of Mars likely caused the greenhouse effect. The study was recently published in Proceedings⁵ of the National Academy⁶ of Sciences.

When water or ice on the surface of a planet evaporates⁷ – which happens when it turns from solid form into a vapor⁸ – it creates humidity⁹. Humidity forms when a high level of water vapor exists in the atmosphere. The vapor helps clouds form.

The researchers say high clouds provide more of a warming effect than low clouds. High clouds would have been more likely to form if only small areas were covered with ice, such as the poles or on mountaintops. They believe this was the case on Mars.

Kite said past studies had considered similar theories, but the research was based on ideas linked to the behavior of our own planet. "In the model, these clouds behave in a very un-Earth-like way," Kite said in a statement.

"Building models on Earth-based" understandings will just not work he said, adding, "this is not at all similar to Earth's water cycle, which moves water quickly between the atmosphere and the surface."

Kite said his team's model suggests that once water moved into the early Martian atmosphere, it likely remained for a much longer time. "And that creates the conditions for long-lived high-altitude clouds."

The team said it hopes the new theory can help scientists resolve¹⁰ a huge "disconnect" between existing evidence about water on Mars and the ability to back it up with physics and chemistry.

Kite added that NASA's Mars explorer Perseverance¹¹ should be able to test the theory in several ways. For example, small rock material could be collected and examined in an effort to recreate past atmospheric¹² pressure on Mars.

The latest study and future research on how Mars gained and lost its warmth could also help scientists identify other habitable worlds, Kite said. "Mars is important because it's the only planet we know of that had the ability to support life -- and then lost it."

Words in This Story

three-dimensional (3D) – adj. having or appearing to have length, depth and height

vapor – n. small drops of liquid in the air

habitable – adj. able to support life

1 Mars   

n.火星，战争

参考例句：

• As of now we don't know much about Mars.目前我们对火星还知之甚少。
• He contended that there must be life on Mars.他坚信火星上面一定有生物。

2 provided   

conj.假如，若是；adj.预备好的，由...供给的

参考例句：

• Provided it's fine we will have a pleasant holiday.如果天气良好，我们的假日将过得非常愉快。
• I will come provided that it's not raining tomorrow.如果明天不下雨，我就来。

3 planet   

n.行星

参考例句：

• Neptune is the furthest planet from the sun. 海王星是离太阳最远的行星。
• Rubbish, however, is only part of the problem of polluting our planet. 然而, 垃圾只是我们这个星球的污染问题的一个方面。

4 greenhouse   

n.花房，温室，玻璃暖房

参考例句：

• Behind the green house was a greenhouse.在那所绿房子后面是一个花房。
• The tomatoes were grown in the greenhouse.这些西红柿是在温室栽培的。

5 proceedings   

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 academy   

n.(高等)专科院校；学术社团，协会，研究院

参考例句：

• This is an academy of music.这是一所音乐专科学院。
• I visited Chinese Academy of Sciences yesterday.我昨天去访问了中国科学院。

7 evaporates   

v.（使某物）蒸发掉( evaporate的第三人称单数 )；消失，不复存在；使脱水

参考例句：

• Heat evaporates water into steam. 水受热变成水蒸气。 来自《简明英汉词典》
• As the water evaporates, a crust of salt is left on the surface of the soil. 随着水分的蒸发，地面上留下了一层结晶盐。 来自辞典例句

8 vapor   

n.蒸汽，雾气

参考例句：

• The cold wind condenses vapor into rain.冷风使水蒸气凝结成雨。
• This new machine sometimes transpires a lot of hot vapor.这部机器有时排出大量的热气。

9 humidity   

n.湿度，潮湿，湿气

参考例句：

• The house is not comfortable tonight ,because of the high humidity.由于湿度高，今晚屋子里不舒服。
• It's difficult to work because of the humidity.由于空气潮湿，工作很困难。

10 resolve   

vt.解决，解除；决定，决心

参考例句：

• It's up to him to resolve this problem.这个问题应由他来解决。
• This did not shake his resolve.这事并未动摇他的决心。

11 perseverance   

n.坚持不懈，不屈不挠

参考例句：

• It may take some perseverance to find the right people.要找到合适的人也许需要有点锲而不舍的精神。
• Perseverance leads to success.有恒心就能胜利。

12 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。