It's quite possible there's as much lightning on Venus as on Earth.

We don't know that Venus had oceans, but there's every reason to believe it did.

Venus and Mars are our next of kin: they are the two most Earth-like planets that we know about. They're the only two other very Earth-like planets in our solar system, meaning they orbit close to the sun; they have rocky surfaces and thin atmospheres.

The story of our species is one of overcoming existential risk through new forms of cooperation and innovation.

I think a lot of people interested in space exploration tend to hear stories about the great missions, how they work technically, what we learned. But they don't really hear the story of what it takes to get a mission from scratch to the launch pad and into space.

A lot of the science fiction that I grew up reading was written when we still thought that Venus might be an oceanic planet.

Even as our unwitting alterations to Earth's carbon and hydrological cycles slowly make storms more damaging, our ability to monitor our planet from space and make reliable short-term forecasts have equipped us enormously to withstand them.

Even as a kid enthralled with science fiction, I wondered about the role of people in the long-term evolution of the Earth, the far future and the fate of humanity.

We're going to stop looking at Earth from orbit because we don't like what we are seeing and the conclusions that leads us to? That's nonsense.

Certainly for me, as an astrobiologist, science fiction has played an important role. One of the quandaries of our field is that we are trying to study and search for something - life - that we can't define in a rigorous way. We only have one example of a biosphere, so we can't really give a good definition.

It's quite possible that the end of us will not be the end of the Earth. Even if we really screw things up and things go badly for us and our civilization, the Earth is pretty resilient.

Earth's biosphere gave birth to humans and our thoughts, which are now reshaping its planetary cycles. A planet with brains? Fancy that.

As long as we can imagine a better path, of course we are obligated to seek it. This is why unwarranted pessimism about our future is actually irresponsible.

The basic ability to not wipe oneself out, to endure, to use your technological interaction with the world in such a way that has the possibility of the likelihood of lasting and not being temporary - that seems like a pretty good definition of intelligence.

Seriously, we should start taxing churches and have tax-exempt places for worship and study of nature and art. Charge ten bucks for Sunday services and make the Botanic Gardens free.

NASA, and all the other spacefaring nations of the world, have agreed to a set of 'planetary-protection' principles, aimed at preventing the accidental contamination of another habitable world with organisms from Earth.

Literally, my earliest memory, my earliest vivid memory, is the Apollo 11 landing on the Moon. Yeah, I was in fourth grade, and I was just so captivated. And I think you'll find a lot of space scientists of my generation will say the same thing. Apollo was a big event for them.

I'm a strong advocate of new missions to Venus.

When you think about alien intelligences making art, you then have to think about what art is and how bound up it is in the nature of consciousness. Why do we make art? And what can we expect to have in common with other creatures in universe?

Part of the point of SETI has always been a search for answers about our own cosmic potential and destiny. If 'they' are out there, it means that there may be hope for us.

Why should we consider defining intelligence as something global and as something that hasn't actually yet appeared on Earth? It may be useful for envisioning the future of our own civilization and any others that may be out there among the stars. It might give us something to strive for.

If we gutted NASA Earth Science, it wouldn't be NOAA or some other agency that would take the lead. It would be the Chinese and the Europeans and the Japanese.

It's OK to pursue speculative ideas because we don't want to be too cozy and safe and assume that we know everything about life in the universe. However, we have to be rigorous and careful and honest and logical and scientifically meticulous when we speculate.

I was a science fiction geek from an early age, enthralled by the questions of life in the universe. As I got older, I learned that space exploration was real. I wanted to get involved in that. I knew I wanted to be a scientist.