Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgments
- PART ONE THE ASTRONOMICAL PLANET: EARTH'S PLACE IN THE COSMOS
- PART TWO THE MEASURABLE PLANET: TOOLS TO DISCERN THE HISTORY OF EARTH AND THE PLANETS
- PART THREE THE HISTORICAL PLANET: EARTH AND SOLAR SYSTEM THROUGH TIME
- PART FOUR THE ONCE AND FUTURE PLANET
- 21 Climate Change Over the Past 100,000 Years
- 22 Human-Induced Global Warming
- 23 Limited Resources: The Human Dilemma
- 24 Coda: The Once and Future Earth
- Index
- Plate section
24 - Coda: The Once and Future Earth
from PART FOUR - THE ONCE AND FUTURE PLANET
- Frontmatter
- Contents
- Preface
- Acknowledgments
- PART ONE THE ASTRONOMICAL PLANET: EARTH'S PLACE IN THE COSMOS
- PART TWO THE MEASURABLE PLANET: TOOLS TO DISCERN THE HISTORY OF EARTH AND THE PLANETS
- PART THREE THE HISTORICAL PLANET: EARTH AND SOLAR SYSTEM THROUGH TIME
- PART FOUR THE ONCE AND FUTURE PLANET
- 21 Climate Change Over the Past 100,000 Years
- 22 Human-Induced Global Warming
- 23 Limited Resources: The Human Dilemma
- 24 Coda: The Once and Future Earth
- Index
- Plate section
Summary
The origin and evolution of Earth involved physical processes that operate on all matter and energy in the universe. The formation of stars is a common phenomenon in galaxies, and we are on the threshold of confirming that the formation of planetary systems is a common result of star formation. Planets, most likely, are extremely common throughout the universe, and the technology to detect planets around other stars is just now available. In the year between October 1995 and September 1996, for example, planets were discovered around six other stars similar to the Sun in our galactic neighborhood.
In our solar system, three rocky planets had the potential early on for supporting life. Venus, Earth, and Mars were all endowed with carbon dioxide atmospheres, and at least Earth and Mars received large influxes of organic materials and water. The presence of a watery ocean was a key early step toward regulating and retaining the atmosphere. The absence or early demise of an ocean on Venus is causal to its present state: With no sink for carbon dioxide in the form of carbonates, all of the carbon dioxide remained as a massive atmosphere supporting a supergreenhouse warming: perpetually too hot to ever permit liquid water to exist.
The evidence is abundant that Mars had a mild, wet climate early on; the absence of plate tectonic recycling of carbon dioxide allowed carbonate formation to permanently lock up carbon dioxide in the crust, progressively cooling the surface and atmosphere until liquid water froze completely.
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- EarthEvolution of a Habitable World, pp. 309 - 310Publisher: Cambridge University PressPrint publication year: 1998