A lot of my role is advocacy, and as a scientist, you're an advocate, too, because you are coming up with a theory and having to convince your fellow scientists that you're right.

One of the big things about space exploration is that it is as expensive as it is complicated, and you need all the countries of the world to help if you want to accomplish big goals.

With the mission to Mars, the whole world wants to get involved. So we actually have 13 different space agencies from around the world working on the global exploration road map.

My key aim is to get man on the surface of Mars by the mid-2030s.

I don't believe that there is anybody who denies climate change in the Democratic caucus. Everybody accepts that it is a real problem.

For me, going vegan was an ethical and environmental decision. I'm doing the right thing by the animals.

Lady Bird Johnson did more than plant flowers in public places. She served the country superbly by planting environmental values in the minds of the nation's leaders and citizens.

The environmental crisis is a global problem, and only global action will resolve it.