If Earth ever suffers a runaway greenhouse effect (like what has happened on Venus), then our atmosphere would trap excess amounts of solar energy, the air temperature would rise, and the oceans would swiftly evaporate into the atmosphere as they sustained a rolling boil. This would be bad.
Some molecules - ammonia, carbon dioxide, water - show up everywhere in the universe, whether life is present or not. But others pop up especially in the presence of life itself. Among the biomarkers in Earth's atmosphere are ozone-destroying chlorofluorocarbons from aerosol sprays, vapor from mineral solvents, escaped coolants from refrigerators and air conditioners, and smog from the burning of fossil fuels. No other way to read that list: sure signs of the absence of intelligence.
Where did the concept of "without borders" come from? No one had that concept until you saw Earth from space, illustrated not by a mapmaker who's color-coding political boundaries; it's illustrated by nature itself and there's land, there's ocean, there's atmosphere.
If NASA were advancing a space frontier there would be challenges you've never seen before. You have to be creative and you have to patent some new idea. You get to Mars...well, how do we get the water from the soil? I gotta invent a new device that will do that. And the carbon dioxide in the atmosphere, how can we use that? Can we breathe the oxygen from the carbon dioxide?
I want to create the airplane that flies in the rarified atmosphere of Mars. This is what galvanizes a generation to want to become scientists and engineers in the first place, not we need a scientist to develop a plane that's 20 percent more fuel-efficient than the one your parents flew.
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