Life in the Cosmos

A rigorous and scientific analysis of the myriad possibilities of life beyond our planet.

“Are we alone in the universe?” This tantalizing question has captivated humanity over millennia, but seldom has it been approached rigorously. Today the search for signatures of extraterrestrial life and intelligence has become a rapidly advancing scientific endeavour. Missions to Mars, Europa, and Titan seek evidence of life. Laboratory experiments have made great strides in creating synthetic life, deepening our understanding of conditions that give rise to living entities. And on the horizon are sophisticated telescopes to detect and characterize exoplanets most likely to harbour life.

Life in the Cosmos offers a thorough overview of the burgeoning field of astrobiology, including the salient methods and paradigms involved in the search for extraterrestrial life and intelligence. Manasvi Lingam and Abraham Loeb tackle three areas of interest in hunting for life “out there”: first, the pathways by which life originates and evolves; second, planetary and stellar factors that affect the habitability of worlds, with an eye on the biomarkers that may reveal the presence of microbial life; and finally, the detection of technological signals that could be indicative of intelligence. Drawing on empirical data from observations and experiments, as well as the latest theoretical and computational developments, the authors make a compelling scientific case for the search for life beyond what we can currently see.

Meticulous and comprehensive, Life in the Cosmos is a master class from top researchers in astrobiology, suggesting that the answer to our age-old question is closer than ever before.

Preface

1. Some Intrinsic Properties of Life
      1.1. Defining life: Does it matter?
      1.2. The requirements for life
      1.3. The Anna Karenina principle

I. The Origin and Evolution of Life on Earth
2. The Pathways to the Origin of Life on Earth
      2.1. When did life originate on Earth?
      2.2. The basic building blocks of life
      2.3. Synthesis of the basic building blocks of life
      2.4. The polymerization of monomers
      2.5. The RNA world
      2.6. Did metabolism arise first?
      2.7. What are the plausible sites for abiogenesis?
      2.8. Mathematical models relating to the origin of life
      2.9. Conclusion
3. The Evolutionary History of Life on Earth
      3.1. The origin of life
      3.2. The diversification of bacteria and archaea
      3.3. Oxygenic photosynthesis
      3.4. The rise of oyxgen and the Great Oxygenation Event
      3.5. Eukaryotes
      3.6. Complex multicellularity
      3.7. Intelligence in animals
      3.8. Technological intelligence
      3.9. Paradigms for major evolutionary events
      3.10. The critical steps model
      3.11. Conclusion

II. Aspects of Extraterrestrial Biospheres
4. Habitability: Stellar Factors
      4.1. The habitable zone and its extensions
      4.2. Stellar winds
      4.3. Stellar electromagnetic radiation
      4.4. Stellar flares and associated space weather phenomena
      4.5. Conclusion
5. Habitability: Planetary Factors
      5.1. The myriad roles of temperature
      5.2. Plate tectonics and habitability
      5.3. Tidal locking and its consequences
      5.4. Atmospheric composition
      5.5. The extent of landmasses and oceans on the surface
      5.6. The distribution of landmasses and oceans
      5.7. Life in the atmosphere
      5.8. Conclusion
6. The Quest for Biosignatures
      6.1. Transiting planets
      6.2. Non-transiting planets
      6.3. Alternative observational constraints on habitability
      6.4. Gaseous biosignatures
      6.5. Surface biosignatures
      6.6. Temporal biosignatures
      6.7. False positives versus real biosignatures
      6.8. Assessing the plausibility of life detection
      6.9. Conclusion
7. Life in Subsurface Oceans
      7.1. Worlds with subsurface oceans within our solar system
      7.2. Temperature profiles of the ice envelopes
      7.3. The habitats for subsurface ocean worlds
      7.4. The routes to abiogenesis on subsurface ocean worlds
      7.5. Ecosystems in planets with subsurface oceans
      7.6. Bioessential elements and subsurface ocean worlds
      7.7. Evolutionary trajectories on subsurface ocean worlds
      7.8. Number of subsurface ocean worlds and the implications for detection
      7.9. Conclusion

III. Aspects of Extraterrestrial Technospheres
8. The Drake Equation and Fermi’s Paradox
      8.1. The Drake equation
      8.2. The great silence: Where is everybody?
      8.3. Conclusion
9. The Quest for Technosignatures
      9.1. Radio technosignatures
      9.2. Optical and infrared technosignatures
      9.3. Modality of interstellar signaling
      9.4. On the classification of technological agents
      9.5. Artifact technosignatures
      9.6. The relative prospects for detecting ETIs
      9.7. Conclusion
10. The Propagation of Life in the Universe
      10.1. History and principles of panspermia
      10.2. Interplanetary and interstellar panspermia
      10.3. Seeking potential signatures of panspermia
      10.4. Interstellar travel via rockets
      10.5. Interstellar travel without onboard fuel
      10.6. Conclusion

Epilogue: Sic Itur Ad Astra
References
Acknowlegments
Index