Mars does not belong to 'America,' nor to Earth, nor to human beings.
— David Grinspoon
Responsible global behaviour is ultimately an act of self-preservation of, by, and for the global beast that modern technological humanity has become.
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.
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.
We're going to get off fossil fuels, no question. We may not do it quickly enough to avoid some pain, and I'm quite worried about that. But by the 22nd century, there's no way we'll be on fossil fuels.
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.
If you were on the surface of Venus, assuming you could see the Sun, which, you know, would be hard because it's so cloudy there, but the Sun would actually rise in the west and set in the east. And, it would do so very, very slowly, because the planet rotates incredibly slowly.
I'd been politically active ever since my parents wheeled me in a stroller in a 'ban the bomb' march in Boston in 1963.
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.
In order to have a decent chance to be a communicating species, you would have to learn to think and plan and act over time scales of a century or a millennium.
We're pretty sure there's plenty of organic material on Pluto. The atmosphere is largely methane, and in sunlight, methane builds organic molecules. We see reddish stuff on the surface that we think is organic material.
There are other planets besides the Earth and Mars. I'd like to remind you that studying Venus is vital to understanding life elsewhere.
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.
The story of our species is one of overcoming existential risk through new forms of cooperation and innovation.
Mars does not have an atmosphere and does not have a magnetic field today, so the planet doesn't have the protection from radiation that our atmosphere and magnetic fields provide us on Earth.
I'm an astrobiologist, and I come from a planetary science background, so in a very broad sense, I study the evolution of planetary environments.
I'm a strong advocate of new missions to Venus.
The future peopling of Mars is much more than a scientific endeavor. It is a step of historic and spiritual importance for the human race.
The mature Anthropocene begins when we acquire the ability to live sustainably and become a lasting presence on this world.
Through space-based climate studies, my colleagues and I have learned that a stable and comfortable climate is not something to take for granted.
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.
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.
It turns out one of my dad's best friends was Carl Sagan when I was little. They were both Harvard professors.
Titan has rivers and lakes of liquid methane and ethane, methane weather systems of clouds and storms that mirror Earth's hydrologic cycle, and seasonal cycles that rival Earth's in complexity.
Ever since the environmental movement was sparked by photos of the whole Earth taken by astronauts onboard Apollo Lunar Modules, I've seen planetary exploration as an extension of a reverence and care for Earth.
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.
What we should really be thinking about is what it would look like for a truly intelligent technological species to be interacting with their planet's atmosphere.
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.
I will defend the NASA Earth Science Division with everything I've got.
You cannot study other planets without referring to Earth and without applying the techniques and the insights of Earth science. And you cannot really do a good job understanding the Earth without the insights from planetary exploration.
Now, humans have become a dominant force of planetary change and, thus, we may have entered an eon of post-biological evolution in which cognitive systems have gained a powerful influence on the planet.
Radiation is one of the important factors in evolution. It causes mutation, and some level of mutation is actually good for evolution.
Earth is going to lose its oceans in the future, just as Venus did in the past. How long planets retain their oceans is a function of distance from the sun, all other things being equal.
We don't know that Venus had oceans, but there's every reason to believe it did.
Once we become a multiplanet species, our chances to live long and prosper will take a huge leap skyward.
Humanity has at least a dim, and growing, cognisance of the effects of its presence on this planet. The possibility that we might integrate that awareness into how we interface with the Earth system is one that should give us hope.
Humans are possessed, to some degree, with the power of foresight. Yet we so often learn things the hard way, through disaster.
Even cynical, selfish people will realize, one way or the other, that it's not in their self-interest to act in self-destructive ways.
I do a lot of work with NASA and am involved in research projects studying planetary evolution, Earth-like planets, and potential conditions for life elsewhere.
A lot of the science fiction that I grew up reading was written when we still thought that Venus might be an oceanic planet.
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.
I think that an advanced planetary civilization will modify their own planets to be more stable, to prevent asteroid impacts and dangerous climate fluctuations.
We have all this very clever technology and all these abilities to manipulate the world in all these ways, yet we are faced with the very real question of whether we can be sustainable on this planet - whether or not, in fact, we can endure.
I think Pluto has to be considered among the places in the solar system that are possible homes for life.
There was a long history of people believing there was life on Venus. It was about the same size as Earth. It had clouds. It was commonly believed it was tropical - wet, hot and steamy.
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.
We need to have a vision of the world we want to create so that we can see ourselves as collaborators with future generations in the project of shaping it.
What I wonder most about the Anthropocene is not when did it start - but when, and how, will it end? Will it end? Or is it possible that our own growing awareness of our role on Earth can itself play a pivotal role in shaping the outcome toward one that we would desire?
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.
As a young planet, Venus was losing hydrogen rapidly to space. The oceans boiled off, and after some period of time, perhaps 600 million years, there was no surface water.
