In some cases, they can only be seen with the latestmapping techniques,like this one in Brazil.

有时候需要专家的绘图技术 才能揭示一个陨石坑的存在比如这个位于巴西的

But even with this technology,less than 200 impactcraters have been found across the entire planet.

但即使是用最精密的设备 在整个地球上 找到的陨石坑也不超过200个

This is partly because erosion continually rubs out the evidence of past impacts,

部分原因是因为腐蚀现象 不断抹去过去冲击的证据

but it's also because of the atmosphere's protective role.

但是也是因为大气层发挥了保护作用

To understand how something as intangible as thin air protects us from meteors,

为了理解像空气这样薄稀的事物 如何保护我们不受陨石侵害

you need to find a meteorite that has survived its fall to Earth.

你需要寻找一个成功掉到地球上来的陨石

Meteorites are rare, so you need to go to great lengths to track one down.

陨石很稀少所以你需要费很大的劲去寻找

Dr Phil Bland is a planetary scientist on just such a mission,

菲尔·布兰德就是一个执行该使命的科学家

leading an expedition out onto the barren NuHarbor Plain

我跟他一起踏上了征程

in Western Australia, three days' drive from the nearest town.

到澳大利亚西部有三天的车程