英语听力：探索发现 科学新发现：我们的大气层-7

 To discover why these twin planets followed separate paths and to explore what gave us our precious atmosphere, we have to travel back, back four and a half billion years to the birth of the solar system itself. 

 

The birth of the solar system created Earth’s earliest atmosphere. Huge quantities of materials orbiting the Sun fused together into proto-planets. Jupiter and Saturn¹ formed into gassy spheres. But on Earth, most of the material condensed into a molten core. The remaining gases bubbled forth² from the liquid rock, forming the first atmosphere. 

 

Our planet’s gravity stopped these gases from drifting off into space. But Earth now had to face the ravages³ of the solar wind, a stream of charged particles thrown out by the Sun. This same wind had a catastrophic effect on Mars. It has stripped the air from the planet’s surface, blasting it deep into space. The Red Planet’s atmosphere is now only a hundredth as thick as Earth’s. 

1 Saturn   

n.农神，土星

参考例句：

• Astronomers used to ask why only Saturn has rings.天文学家们过去一直感到奇怪，为什么只有土星有光环。
• These comparisons suggested that Saturn is made of lighter materials.这些比较告诉我们，土星由较轻的物质构成。

2 forth   

adv.向前；向外，往外

参考例句：

• The wind moved the trees gently back and forth.风吹得树轻轻地来回摇晃。
• He gave forth a series of works in rapid succession.他很快连续发表了一系列的作品。

3 ravages   

劫掠后的残迹，破坏的结果，毁坏后的残迹

参考例句：

• the ravages of war 战争造成的灾难
• It is hard for anyone to escape from the ravages of time. 任何人都很难逃避时间的摧残。