听力文摘：月球地表形态的无限保质期

In 1969 when Neil Armstrong said "That's one small step…", he made a lasting¹ impression. On the moon, that is.

1969年阿姆斯特朗的那句"人类一小步。"给人留下了难以磨灭的印象。

Marks on the surface of the moon don't disappear the way marks on the Earth do; a great example is the impact craters² we can see dotting the moon's surface.

月球表面的记号不会像地球那样轻易地消失。最典型的例子就是我们肉眼可见的月球表面散布的陨石坑。

Many of them are billions of years old!

这些陨石坑中很多有数十亿年的历史。

But Why?

但为什么呢？

If you write your name in the sand at the beach, one day later there's no sign you were there. What's the difference?

如果你用沙子在沙滩上写下你的名字的话，一天过后，名字就会消失。差别在哪呢？

Here's an experiment you can do to find out. Take two pans and fill them with soil and sand mixed together.

你可以做个实验来找出这种差别。拿出两个平底锅，里面放满土和沙子并将土和沙子掺在一起。

Now have some young person press her or his hand down into the mixture to make an imprint³. One of these surfaces will represent the Earth, and one the moon.

然后找几个年轻人把手放在沙土中摁出手印。其中一个平底锅代表地球，另一个代表月球。

Leave your Earth pan outside. Take the moon pan inside and place a cardboard box over the top of it, weighted down with something heavy. Wait a couple days and check again.

把代表地球的平底锅放在户外，然后把代表月球的平底锅放在室内并在它的上面放上一个硬纸盒，再压上一些重物。几天过后再进行观察。

The moon pan will look the same. More than likely, though, the Earth pan won't. Maybe the wind blew the sand around. Maybe it rained or snowed.

你会发现代表月球的平底锅没有任何变化。但代表地球的平底锅却并非如此，也许是风把沙子吹得到处都是，也许是被雨雪冲刷过。

The point is that Earth has an atmosphere, which results in wind, rain, rivers and streams, lots of motion.

答案就在于地球有一层大气，大气可以产生风、雨、河流、小溪等引起运动的事物。

Of course, Earth is also volcanically⁴ active: the ground shakes, lava⁵ pours out, continents rise and fall.

当然，地球的火山运动是非常活跃的，会造成地震、岩浆喷发、大陆沉降。

By comparison, nothing much ever happens on the moon–except for the impacts that give rise to those craters–even across billions of years.

相比之下，月球在数十亿年里基本不会产生这些现象（形成火山坑的撞击除外）。

So an impression on the moon can be a lasting impression indeed!

因此，你在月球上留下的印记会一直留在那哦！

1 lasting   

adj.永久的，永恒的；vbl.持续，维持

参考例句：

• The lasting war debased the value of the dollar.持久的战争使美元贬值。
• We hope for a lasting settlement of all these troubles.我们希望这些纠纷能获得永久的解决。

2 craters   

n.火山口( crater的名词复数 )；弹坑等

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》
• The battlefield was full of craters made by exploding shells. 战场上布满弹坑。 来自《现代英汉综合大词典》

3 imprint   

n.印痕，痕迹；深刻的印象；vt.压印，牢记

参考例句：

• That dictionary is published under the Longman imprint.那本词典以朗曼公司的名义出版。
• Her speech left its imprint on me.她的演讲给我留下了深刻印象。

4 volcanically   

adv.火山似地，猛烈地

参考例句：

5 lava   

n.熔岩，火山岩

参考例句：

• The lava flowed down the sides of the volcano.熔岩沿火山坡面涌流而下。
• His anger spilled out like lava.他的愤怒像火山爆发似的迸发出来。