An asteroid can literally destroy 80 or 90 percent of the species that are alive on Earth. These are big events. I mean, this is called extinction.

In the short term, some deadly virus might be more important, but in the long run there is hardly anything more important than asteroids.

By preventing dangerous asteroid strikes, we can save millions of people, or even our entire species. And, as human beings, we can take responsibility for preserving this amazing evolutionary experiment of which we and all life on Earth are a part.

For the first time in history, we have the chance to change the path of a celestial body. Let's realize what we're talking about here. We would be slightly changing the mechanics of our solar system to enhance our survival. That is gigantic!

Anytime we can save lives or prevent the destruction of property, we should do it.

There's no accepted global policy on what to do about asteroid impacts.

While we didn't know the dinosaurs personally, we do know that they were wiped out by an asteroid impact.

So I just let go with one hand, and just sort of swung around, looked at the Earth below and the black space above and the sun over my shoulder. And, I mean, it was this incredible, spectacular view.

Asteroids have hit the Earth millions of times. We can see them as shooting stars every night. When they get bigger, things get complicated. It is only a matter of time until a big one hits us. And since we can do something about it, we should.

As you pass from sunlight into darkness and back again every hour and a half, you become startlingly aware how artificial are thousands of boundaries we've created to separate and define. And for the first time in your life you feel in your gut the precious unity of the Earth and all the living things it supports.

It would take an extremely large spacecraft to deflect a large asteroid that would be headed directly for the Earth.

You almost wish you could turn off the COMM and just appreciate the deafening quiet.

I am interested in climate change and other topics too. But this thing is so huge, in the worst case we are talking about the end of our civilization.

We need early warning systems, technologies to deflect an asteroid - and we need political preparedness as well. It needs to be clear who is to decide what, who launches the rockets, who presents which bills to its citizens. This is a planetary decision. We need to do this all together. Or it will not happen.

We can both prevent asteroid impacts and address climate change. It's not either-or.

If we do our homework right, never again should an asteroid that can do damage on the ground impact the Earth. We're living in a time-with our technology-we have the capability to eliminate that major shaper of evolution . . . the evolution of life on this planet.