American - Scientist | 1959 -
In my Ph.D. thesis, written in 1989, I discussed the fact that when a civilization develops the technology to prevent catastrophic asteroid impacts, it marks a significant moment in the evolution of the planet.
David Grinspoon
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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.
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It will be a long time, if ever, before we get to study Earth-like planets orbiting around other stars, so really, the study of Venus and Mars is the best opportunity that we have, and can imagine having anytime in the future, to understand the evolution of Earth-like planets.
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We don't know that Venus had oceans, but there's every reason to believe it did.
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I'm a strong advocate of new missions to Venus.
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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.
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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.
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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.
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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.
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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.
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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?
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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.
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