David Grinspoon

My high-school friends and I felt part of a community of smart, forward-looking space and technology freaks.

We've almost been wiped out as a species many times, going back millions of years, and we've survived by reinventing ourselves and enlarging our circles of awareness, inventing new technologies and social structures.

In environments that are energy-rich but liquid-poor, like near the surface of Titan, natural selection may favor organisms that use their metabolic heat to melt their own watering holes.

I think chemists always think they know more than they know, because nature has a lot of possible pathways it can try.

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.

I do comparative studies of climate evolution, and the interactions between planetary atmosphere and surfaces and their radiation environment, and try to understand the environmental factors that can affect a planet's habitability and how they change over time.

The more we look at the kinds of soils and the nature of the atmosphere and the polar caps, it all adds up to tell us that some liquid, which we very much believe was water, did flow in abundance on Mars in the past.

As Earth's climate changes, we can expect more destructive hurricanes. As sea level and surface temperatures rise, more solar energy is trapped in the atmosphere, revving up the hydrological cycle of evaporation and precipitation and sometimes manifesting in terrifying storms.

Humans are possessed, to some degree, with the power of foresight. Yet we so often learn things the hard way, through disaster.

The hallmark of the human species is great adaptability.

Thinking about the new epoch - often called the Anthropocene, or the age of humanity - challenges us to look at ourselves in the mirror of deep time, measured not in centuries or even in millennia, but over millions and billions of years.

We definitely don't want to go through another Ice Age or another natural cycle of global warming. Both happen over a long period of time. It would be disastrous for our civilization, and not just for us but many other species.