With one linear centimeter of your lower colon there lives and works more bacteria (about 100 billion) that all humans who have ever been born. Yet many people continue to assert that it is we who are in charge of the world

If you want to assert a truth, first make sure it's not just an opinion that you desperately want to be true.

The tenacity of life is mind-boggling. We keep finding it where no one thought it could be.

Mars once was wet and fertile. It's now bone dry. Something bad happened on Mars. I want to know what happened on Mars so that we may prevent it from happening here on Earth.

But to carve the Grand Canyon, Earth required millions of years. To excavate Meteor Crater, the universe, using a sixty-thousand-ton asteroid traveling upward of twenty miles per second, required a fraction of a second. No offense to Grand Canyon lovers, but for my money, Meteor Crater is the most amazing natural landmark in the world.

I see myself in pop culture. I listen to pop music, I do pop things, and I'm also a scientist.

Just before I said I wanted to be an astronomer I said I wanted to be a baseball player. I was quite athletic at the time, probably because I was bigger than other kids, and if you're bigger than other kids and you're 11 you win everything.