Hints: Volcano Mars Earth the Grand Canyon carbon, oxygen, nitrogen lights-are-on-but-nobody's-home

Volcanoes and explosions had clearly once torn across this planet, leaving the surface pockmarked and scarred. Far from being dead, Mars had all the features of once being very much alive. We started seeing all these incredible things. It has mountains there bigger than any mountains on Earth. It's got canyons that are bigger than the Grand Canyon. All these volcanoes, parts of Mars was cratered, parts weren't. It's got tremendous altitude variations over the surface of the planet. It's just a very rich environment. So that was a very exciting, exciting time. I was surprised by almost everything. It wasn't just the geology of Mars that was surprising. It also contained all the basic ingredients for life. Here was a planet that had all the elements needed for life, carbon, oxygen, nitrogen, sunlight. And yet there was no clear evidence of life. To me this was a mystery story; it was a sort of lights-are-on-but-nobody's-home result. So life could form on Mars. There's nothing there preventing it. We do have the basic building blocks.

这篇材料你能听出多少？点击这里做听写，提高外语水平>>