How to Find a Habitable Planet

by Kasting, James F.

• ISBN13: 9780691138053
• ISBN10: 0691138052
• Format: Hardcover
• Copyright: 2009-12-28
• Publisher: Princeton Univ Pr

Summary

Ever since Carl Sagan first predicted that extraterrestrial civilizations must number in the millions, the search for life on other planets has gripped our imagination. Is Earth so rare that advanced life forms like us--or even the simplest biological organisms--are unique to the universe?How to Find a Habitable Planetdescribes how scientists are testing Sagan's prediction, and demonstrates why Earth may not be so rare after all.James Kasting has worked closely with NASA in its mission to detect habitable worlds outside our solar system, and in this book he introduces readers to the advanced methodologies being used in this extraordinary quest. He addresses the compelling questions that planetary scientists grapple with today: What exactly makes a planet habitable? What are the signatures of life astronomers should look for when they scan the heavens for habitable worlds? In providing answers, Kasting explains why Earth has remained habitable despite a substantial rise in solar luminosity over time, and why our neighbors, Venus and Mars, haven't. If other Earth-sized planets endowed with enough water and carbon are out there, he argues, chances are good that some of those planets sustain life. Kasting describes the efforts under way to find them, and predicts that future discoveries will profoundly alter our view of the universe and our place in it.This book is a must-read for anyone who has ever dreamed of finding other planets like ours--and perhaps even life like ours--in the cosmos.

Table of Contents

Preface	p. xi
Introduction	p. 1
Past Thinking about Earth-Like Planets and Life	p. 3
The Habitable Zone and the Importance of Liquid Water	p. 5
Carl Sagan and the Drake Equation	p. 9
Other Perspectives on Planetary Habitability: Rare Earth and Gaia	p. 11
Our Habitable Planet Earth	p. 15
Critical Updates on How Planets Are Built	p. 17
The Conventional Wisdom regarding Planet Formation	p. 18
Where Did Earth's Water Come From?	p. 21
New Models for Planetary Accretion and Delivery of Water	p. 23
Could Earth's Water Have Come from Comets?	p. 25
An Up-to-Date Simulation of Planetary Accretion	p. 28
Long-Term Climate Stability	p. 32
Solar Evolution Theory	p. 32
Solar Mass Loss?	p. 36
Electromagnetic Radiation and the Greenhouse Effect	p. 37
Planetary Energy Balance	p. 41
The Faint Young Sun Problem	p. 42
Possible Solutions to the Problem	p. 45
The Carbonate-Silicate Cycle and Controls on Atmospheric CO2	p. 49
The CO2-Climate Feedback Loop	p. 53
More Wrinkles in Earths Climate History	p. 57
The Phanerozoic Climate Record	p. 58
Precambrian Climate	p. 63
Geologic Evidence for the Rise of Atmospheric O2	p. 65
Cause of the O2 Rise: Cyanobacteria	p. 68
Methane, Methanogens, and the Universal Tree of Life	p. 71
The Archean Methane Greenhouse	p. 75
The Paleoproterozoic Glaciation	p. 77
Runaway Glaciation and "Snowball Earth"	p. 80
Milankovitch Cycles and the Recent Ice Ages	p. 81
Ice Albedo Feedback and Climatic Instability	p. 86
Evidence for Low-Latitude Glaciation	p. 88
Mechanisms for Explaining Low-Latitude Glaciation	p. 90
Snowball Earth	p. 92
Limits to Planetary Habitability	p. 97
Runaway Greenhouses and the Evolution of Venus' Atmosphere	p. 99
The History of Water on Venus	p. 100
The Classical Runaway Greenhouse Effect	p. 103
An Alternative Runaway Greenhouse Model	p. 106
Evolution of Venus' Atmosphere	p. 111
The Future Evolution of Earth	p. 116
High-CO2 Atmospheres and Temperature Limits for Life	p. 116
Future Solar Evolution and Lifetime of the Biosphere	p. 118
A Geoengineering Solution to Solar Luminosity Increases	p. 121
The Martian Climate Puzzle	p. 125
Evidence for Liquid Water near Mars' Surface	p. 126
CH4 in Mars' Atmosphere?	p. 130
Evidence That Water Flowed in Mars' Distant Past	p. 131
When Did the Martian Valleys Form?	p. 135
How Warm Was Early Mars?	p. 136
Mechanisms for Warming Early Mars	p. 138
Where Are the Carbonates?	p. 144
Is the Earth Rare?	p. 147
Planetary Size / Magnetic Fields	p. 147
Ozone and Ultraviolet Radiation	p. 152
Availability of Nitrogen and the Importance of N2	p. 155
Is Plate Tectonics Common?	p. 157
A Planets Impact Environment	p. 161
Stabilization of Earth's Obliquity by the Moon	p. 164
Habitable Zones around Stars	p. 171
Historical Attempts to Define the Habitable Zone	p. 171
A More Modern Model for the Habitable Zone around the Sun	p. 176
Hertzsprung-Russell Diagrams and Main Sequence Stars	p. 179
Habitable Zones around Other Stars	p. 181
Problems for Planets Orbiting Early-Type Stars	p. 185
Problems for Planets Orbiting Late-Type Stars	p. 188
Further Extensions of the Habitable Zone Concept	p. 191
The Galactic Habitable Zone	p. 192
How to Find Another Earth	p. 195
Indirect Detection of Planets around Other Stars	p. 197
Barnard's Star	p. 198
The Astrometric Method	p. 199
Pulsar Planets	p. 205
The Doppler Effect	p. 207
The Radial Velocity Method	p. 210
Gravitational Microlensing	p. 216
Finding and Characterizing Planets by Using Transits	p. 221
Transits of Mercury and Venus	p. 221
Transits of Extrasolar "Hot Jupiters"	p. 222
Space-Based Transit Searches: CoRoT and Kepler	p. 227
Observing Exoplanet Atmospheres during Transits	p. 229
Secondary Transit Spectroscopy	p. 233
Characterizing Earth-Like Planets around M Stars	p. 235
Direct Detection of Extrasolar Planets	p. 239
What Wavelength Region Should We Choose?	p. 240
Infrared Interferometers: TPF-I and Darwin	p. 245
Searching for Planets at Visible Wavelengths: TPF-C	p. 248
The Visible Occulter: TPF-O	p. 253
Nearby Target Stars	p. 254
The Spectroscopic Search for Life	p. 258
Spectral Resolution	p. 259
The Visible/Near-IR Region: TPF-C or -O	p. 260
The Thermal-IR Region: TPF-I or Darwin	p. 266
Looking for Life on Early Earth-Type Planets	p. 269
Possible False Positives for Life	p. 271
Polarization Measurements: Looking for the Glint of Surface Water	p. 274
The Holy Grail: Simultaneous Detection of O2 and Reduced Gases	p. 276
Prospects for the More Distant Future	p. 284
NASA's Life Finder Mission	p. 284
Using the Sun as a Gravitational Lens	p. 287
The Drake Equation Revisited: The Search for Extraterrestrial Intelligence	p. 290
Notes	p. 299
Index	p. 317
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