Astrobiology - Charles S. Cockell - E-Book

Astrobiology E-Book

Charles S. Cockell

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A guide to understanding the formation of life in the Universe The revised and updated second edition of Astrobiology offers an introductory text that explores the structure of living things, the formation of the elements required for life in the Universe, the biological and geological history of the Earth, and the habitability of other planets. Written by a noted expert on the topic, the book examines many of the major conceptual foundations in astrobiology, which cover a diversity of traditional fields including chemistry, biology, geosciences, physics, and astronomy. The book explores many profound questions such as: How did life originate on Earth? How has life persisted on Earth for over three billion years? Is there life elsewhere in the Universe? What is the future of life on Earth? Astrobiology is centered on investigating the past and future of life on Earth by looking beyond Earth to get the answers. Astrobiology links the diverse scientific fields needed to understand life on our own planet and, potentially, life beyond. This new second edition: * Expands on information about the nature of astrobiology and why it is useful * Contains a new chapter "What is Life?" that explores the history of attempts to understand life * Contains 20% more material on the astrobiology of Mars, icy moons, the structure of life, and the habitability of planets * New 'Discussion Boxes' to stimulate debate and thought about key questions in astrobiology * New review and reflection questions for each chapter to aid learning * New boxes describing the careers of astrobiologists and how they got into the subject * Offers revised and updated information throughout to reflect the latest advances in the field Written for students of life sciences, physics, astronomy and related disciplines, the updated edition of Astrobiology is an essential introductory text that includes recent advances to this dynamic field.

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Table of Contents

Cover

Acknowledgments

About the Companion Website

1 Astrobiology

1.1 Introductory Remarks

1.2 The Major Questions of Astrobiology and the Content of the Textbook

1.3 Some Other Features of the Textbook

1.4 A Brief History of Astrobiology

1.5 Conclusions

Bibliography

2 What Is Life?

2.1 The Concept of “Life”

2.2 What Is Life? The Historical Perspective

2.3 Spontaneous Generation

2.4 More Modern Concepts

2.5 Schrödinger and Life

2.6 Life as a Dissipative Process

2.7 Life: Just a Human Definition?

2.8 Does It Matter Anyway?

2.9 Conclusions

Bibliography

3 Matter and Life

3.1 Matter and Life

3.2 Life Is Made of “Ordinary” Matter

3.3 The Atomic Nucleus

3.4 Electrons, Atoms, and Ions

3.5 Types of Bonding in Matter

3.6 Ionic Bonding

3.7 Covalent Bonding

3.8 Metallic Bonding

3.9 Van der Waals Interactions

3.10 Hydrogen Bonding

3.11 An Astrobiological Perspective

3.12 The Equation of State Describes the Relationship Between Different Types of Matter

3.13 Other States of Matter

3.14 The Interaction Between Matter and Light

3.15 Conclusions

Bibliography

4 The Molecular Structure of Life

4.1 Building Life

4.2 The Essential Elements: CHNOPS

4.3 Carbon Is Versatile

4.4 The Chains of Life

4.5 Proteins

4.6 Chirality

4.7 Carbohydrates (Sugars)

4.8 Lipids

4.9 The Nucleic Acids

4.10 The Solvent of Life

4.11 Alternative Chemistries

4.12 The Structure of Life and Habitability

4.13 Conclusions

Bibliography

5 The Cellular Structure of Life

5.1 From Molecules to Cells

5.2 Types of Cells

5.3 Shapes of Cells

5.4 The Structure of Cells

5.5 The Structure of Cellular Membranes

5.6 The Information Storage System of Life

5.7 Eukaryotic Cells

5.8 The Reproduction of Cells

5.9 Why Did Sexual Reproduction Evolve?

5.10 The Growth of Populations of Cells

5.11 Moving and Communicating

5.12 Viruses

5.13 Prions

5.14 Conclusions

Bibliography

6 Energy for Life

6.1 Energy and Astrobiology

6.2 Life and Energy

6.3 The Central Role of Adenosine Triphosphate

6.4 Chemiosmosis and Energy Acquisition

6.5 What Types of Electron Donors and Acceptors Can Be Used?

6.6 Aerobic Respiration

6.7 Anaerobic Respiration

6.8 Fermentation

6.9 Chemoautotrophs: Changing the Electron Donor

6.10 Energy from Light: Photosynthesis

6.11 Oxygenic Photosynthesis

6.12 Anoxygenic Photosynthesis

6.13 Rhodopsins and Photosynthesis

6.14 Evolution of Photosynthesis

6.15 Global Biogeochemical Cycles

6.16 Microbial Mats – Energy-Driven Zonation in Life

6.17 The Thermodynamics of Energy Acquisition and Life

6.18 Energy and Life in Extremes

6.19 Conclusions

Bibliography

7 The Limits of Life

7.1 The Limits of Life

7.2 The Importance of the Limits of Life for Astrobiology

7.3 The Most Extreme Conditions are Dominated by Microbes

7.4 Life at High Temperatures

7.5 Life at Low Temperatures

7.6 Salt-Loving Organisms

7.7 pH Extremes

7.8 Life Under High Pressure

7.9 Tolerance to High Radiation

7.10 Life in Toxic Brews

7.11 Rocks as a Habitat

7.12 Polyextremophiles – Dealing with Multiple Extremes

7.13 Life Underground

7.14 Dormancy in Extreme Conditions

7.15 Eukaryotic Extremophiles

7.16 Are There Other Biospheres with Different Limits?

7.17 The Limits of Life: Habitability Revisited

7.18 Conclusions

Bibliography

8 The Tree of Life

8.1 A Vast Quantity of Life

8.2 Evolution and a “Tree of Life”

8.3 Classifying Organisms

8.4 The Tree of Life and Some Definitions

8.5 Problems with Classification: Homology and Analogy

8.6 Building a Phylogenetic Tree Using Genetic Material

8.7 Types of Phylogenetic Trees

8.8 A Modern View of the Tree of Life

8.9 Using Phylogenetic Trees to Test Hypotheses

8.10 Complications in Building Trees

8.11 Origin of Eukaryotes

8.12 The Last Universal Common Ancestor

8.13 Multiple Origins of Life?

8.14 Alien Life

8.15 Conclusions

Bibliography

9 The Universe, the Solar System, and the Elements of Life

9.1 Our Cosmic Situation

9.2 In the Beginning: The Formation of the Universe

9.3 Stellar Evolution: Low-Mass Stars

9.4 Stellar Evolution: High-Mass Stars

9.5 The Elements of Life

9.6 The Hertzsprung–Russell Diagram

9.7 The Sun Is a Blackbody

9.8 The Formation of Planets

9.9 Types of Objects in Our Solar System

9.10 Meteorites and Their Classification

9.11 Laws Governing the Motion of Planetary Bodies

9.12 Conclusions

Bibliography

10 Astrochemistry: Carbon in Space

10.1 Astrochemistry: Carbon Molecules in Space

10.2 Observing Organics

10.3 In the Beginning

10.4 Different Environments for Chemistry

10.5 How Do Chemical Reactions Occur?

10.6 Forming Carbon Compounds

10.7 Formation of Water

10.8 Interstellar Grains

10.9 Polycyclic Aromatic Hydrocarbons

10.10 Even More Carbon Diversity

10.11 Comets and Organic Molecules

10.12 The Origin of Chirality

10.13 Laboratory Experiments

10.14 Observing Organic Molecules

10.15 Conclusions

Bibliography

11 Early Earth: The First Billion Years

11.1 The First Billion Years of Earth

11.2 Earth Forms and Differentiates

11.3 The Formation of the Moon

11.4 The Early Oceans

11.5 The Early Crust

11.6 The Early Atmosphere

11.7 The Temperature of Early Earth

11.8 The Late Heavy Bombardment

11.9 Implications of the Early Environment for Life

11.10 Conclusions

Bibliography

12 The Origin of Life

12.1 The Origin of Life

12.2 The Synthesis of Organic Compounds on Earth

12.3 Delivery from the Extraterrestrial Environment

12.4 The RNA World

12.5 Early Cells

12.6 Where Did the Origin of Life Occur?

12.7 A Cold Origin of Life?

12.8 The Whole Earth as a Reactor?

12.9 Conclusions

Bibliography

13 Early Life on Earth

13.1 Early Life on Earth

13.2 Early Life – Metabolisms and Possibilities

13.3 Isotopic Fractionation

13.4 Measuring the Isotope Fractionation: The Delta Notation

13.5 Sulfur Isotope Fractionation

13.6 Using Isotopes to Look for Ancient Life

13.7 Morphological Evidence for Life

13.8 Biomarkers

13.9 Contamination Is a Problem

13.10 Instruments Used to Look for Life

13.11 A Brief Summary

13.12 The Search for Extraterrestrial Life

13.13 Conclusions

Bibliography

14 The Geology of a Habitable World

14.1 The Geological History of Earth: A Habitable World

14.2 Minerals and Glasses

14.3 Types of Rocks

14.4 The Rock Cycle

14.5 The Composition of Earth

14.6 Plate Tectonics

14.7 Dating the Age of the Earth (and Other Planetary Bodies)

14.8 Age-Dating Rocks

14.9 Geological Timescales

14.10 The Major Classifications of Geological Time

14.11 Some Geological Times and Biological Changes

14.12 Conclusions

Bibliography

15 The Co-evolution of Life and a Planet: The Rise of Oxygen

15.1 Dramatic Changes on Earth

15.2 Measuring Oxygen Through Time

15.3 It Was Not a Simple Rise

15.4 Summarizing the Evidence for the GOE

15.5 The Source of Oxygen

15.6 Sinks for Oxygen

15.7 Why Did Atmospheric Oxygen Concentrations Rise?

15.8 Snowball Earth Episodes

15.9 Other Biological Consequences of the Rise of Oxygen

15.10 Oxygen and the Rise of Animals

15.11 Oxygen and the Rise of Intelligence

15.12 Periods of High Oxygen

15.13 Conclusions

Bibliography

16 Mass Extinctions

16.1 Extinctions

16.2 What Is Extinction?

16.3 Five Major Mass Extinctions

16.4 Other Extinctions in Earth History

16.5 Causes of Mass Extinction

16.6 The End-Cretaceous Extinction

16.7 The Other Four Big Extinctions of the Phanerozoic

16.8 Do Microorganisms Go Extinct?

16.9 Recovery from Extinction

16.10 Can We Avoid Extinction?

16.11 The Sixth Mass Extinction?

16.12 Conclusions

Bibliography

17 The Habitability of Planetary Bodies

17.1 What Is “Habitability”?

17.2 The Habitable Zone

17.3 Maintaining Temperature Conditions on a Planet Suitable for Water and Life

17.4 Plate Tectonics and Habitability

17.5 Does the Moon Play a Role in Habitability?

17.6 Other Planetary Factors that Influence Habitability

17.7 Surface Liquid Water, Habitability, and Intelligence

17.8 Habitable Environments Need Not Always Contain Life

17.9 Worlds More Habitable than Earth?

17.10 The Anthropic Principle and Habitability

17.11 The Fate of Earth

17.12 The Galactic Habitable Zone

17.13 The Right Galaxy?

17.14 Conclusions

Bibliography

18 The Astrobiology of Mars

18.1 Mars and Astrobiology

18.2 Martian Geological History: A Very Brief Summary

18.3 The Environmental Deterioration of Mars

18.4 Missions to Mars

18.5 Mars and Life

18.6 Trajectories of Martian Habitability

18.7 The Viking Program and the Search for Life

18.8 Searching for Life by Investigating Gases

18.9 Martian Meteorites

18.10 Mars Analog Environments

18.11 Panspermia: The Transfer of Life between Planets?

18.12 Conclusions

Bibliography

19 Ocean Worlds and Icy Moons

19.1 The Astrobiology of Moons

19.2 The Moons of Jupiter: Europa

19.3 The Moons of Jupiter: Ganymede and Callisto

19.4 The Moons of Jupiter: Io

19.5 The Moons of Saturn: Enceladus

19.6 The Moons of Saturn: Titan

19.7 Other Icy Worlds

19.8 Planetary Protection

19.9 Conclusions

Bibliography

20 Exoplanets and the Search for Life

20.1 Exoplanets and Life

20.2 Detecting Exoplanets

20.3 Exoplanet Properties

20.4 Detecting Life

20.5 Surface Biosignatures

20.6 How Likely Are These Signatures?

20.7 Other Ways to Find Life

20.8 Missions to Detect Biosignatures

20.9 Conclusions

Bibliography

21 The Search for Extraterrestrial Intelligence

21.1 The Search for Extraterrestrial Intelligence (SETI)

21.2 Methods in the Search for Extraterrestrial Intelligence

21.3 Communication with Extraterrestrial Intelligence (CETI)

21.4 The Drake Equation

21.5 The Fermi Paradox

21.6 Classifying Civilizations

21.7 Policy Implications

21.8 Conclusions

Bibliography

22 Our Civilization

22.1 Astrobiology and Human Civilization

22.2 The Emergence of Human Society

22.3 Threats to a Civilization

22.4 Climate Change and the Challenge to Civilization

22.5 The Human Future Beyond Earth

22.6 Settling the Solar System

22.7 Avoiding Extinction or Collapse: A Multiplanet Species

22.8 Environmentalism and Space Exploration as a Single Goal?

22.9 Sociology: The Overview Effect

22.10 Will We Become Interstellar?

22.11 Conclusions

Bibliography

Appendix

A.1 The Astrobiology Periodic Table

A.2 Units and Scales

A.3 Temperature Scale Conversion

A.4 Composition of the Sun

A.5 Some of the Major Star Types, Temperatures, and Colors

A.6 Three- and One-Letter Designations of Amino Acids

A.7 Codon Table for the Genetic Code Associated with mRNA (also shown in Chapter 5; Figure 5.12)

A.8 Planetary Data

A.9 Geological Time Scale

Glossary

Index

End User License Agreement

List of Tables

Chapter 1

Table 1.1 The content of the textbook.

Chapter 4

Table 4.1 A range of possible solvents for life, their temperature ranges, heat...

Chapter 6

Table 6.1 Some examples of chemoautotrophic redox reactions.

Chapter 7

Table 7.1 Examples of microbial extremophiles (italics) and extremotolerant (bo...

Table 7.2 Some examples of products (mainly enzymes) and processes involving ex...

Chapter 8

Table 8.1 Some examples of genes that can be sequenced and used to build phylog...

Chapter 10

Table 10.1 A selection of the chemical formulae for just 25 gas phase carbon mo...

Chapter 12

Table 12.1 Some of the compounds generated in the Miller–Urey experiment by mix...

Table 12.2 Some examples of carbon compounds identified in carbonaceous chondri...

Chapter 13

Table 13.1 Typical isotope standards.

Table 13.2 Some example methods used to study ancient life in the rock record....

Chapter 14

Table 14.1 Some examples of common isotopes used to date rocks with their half-...

Chapter 16

Table 16.1 The five major extinctions of the Phanerozoic.

Chapter 18

Table 18.1 A non-exhaustive list of examples of potential redox couples for lif...

Chapter 20

Table 20.1 Some example biosignature gases and their absorption spectral band c...

List of Illustrations

Chapter 1

Figure 1.1 Astrobiology seeks to understand the phenomenon of life in its co...

Figure 1.2 Astrobiology requires an understanding of astronomy. At the end o...

Figure 1.3 The future of the Earth is a topic in astrobiology. When the Sun ...

Figure 1.4 The one example we have of a planet that harbors life: Earth. Ast...

Figure 1.5 A schematic of the history of Earth. Understanding this history a...

Figure 1.6 Habitable worlds orbiting other stars. As this artist's impressio...

Figure 1.7 Astrobiology is concerned with the human future beyond the Earth....

Figure 1.8 Metrodorus of Chios, ancient Greek philosopher. He wondered about...

Figure 1.9 Nicolaus Copernicus, renaissance mathematician and astronomer. He...

Figure 1.10 Giordano Bruno, Dominican friar, mathematician, and philosopher....

Figure 1.11 The “canals” of Mars as depicted by astronomer Percival Lowell. ...

Figure 1.12 Lunar craters. In the eighteenth century, the almost perfectly c...

Figure 1.13 One of the first orbital photographs of Mars, taken by the Marin...

Figure 1.14 Plumes of water emanating from the south polar region of Saturn'...

Figure 1.15 Gavriil Tikhov, who wrote an early book called Astrobiology. He ...

Figure 1.16 Nobel Laureate Joshua Lederberg. He was at the forefront of the ...

Chapter 2

Figure 2.1 Democritus. Ancient Greek philosopher. He proposed an early atomi...

Figure 2.2 Aristotle, ancient Greek philosopher and early natural historian.

Figure 2.3 Disproving spontaneous generation. A schematic diagram showing Fr...

Figure 2.4 Louis Pasteur, microbiologist. He took on the idea of spontaneous...

Figure 2.5 Louis Pasteur's swan neck flasks and his experiment to disprove s...

Figure 2.6 Complexity in matter. A tornado, such as this one in Manitoba, Ca...

Figure 2.7 A wildfire burns organic carbon in oxygen to produce carbon dioxi...

Figure 2.8 Life grows, but crystals do as well. These salt (NaCl) crystals c...

Figure 2.9 Viruses as biological entities. A virus cannot reproduce on its o...

Figure 2.10 A mule is a sterile creature, which means that it cannot reprodu...

Figure 2.11 Erwin Schrödinger. He attempted to understand life from a ...

Figure 2.12 Complex structures can emerge in non-biological dissipative stru...

Figure 2.13 Gold can be uniquely defined using physical characteristics such...

Figure 2.14 Perhaps life is more like a chair? Something whose definition de...

Chapter 3

Figure 3.1 A very simplified depiction of the structure of a typical atom sh...

Figure 3.2 Schematic diagram of the three isotopes of carbon. The number of ...

Figure 3.3 A diagram showing the second shell in an atom and the nomenclatur...

Figure 3.4 The structure of NaCl showing the alternating sodium and chloride...

Figure 3.5 A typical protein. The colored ribbons and lines depict the chain...

Figure 3.6 An ionic bond in a protein formed between two amino acids, the po...

Figure 3.7 The covalent bond in the hydrogen molecule. The two electrons are...

Figure 3.8 As well as holding atoms together in molecules, covalent bonds li...

Figure 3.9 An enhanced number of covalent bonds in proteins is used in some ...

Figure 3.10 Metallic bonding showing a “sea” of delocalized electrons around...

Figure 3.11 The dipoles of two HCl molecules involved in Keesom interactions...

Figure 3.12 An induced dipole in the otherwise uncharged neon is an example ...

Figure 3.13 Charge imbalance (exaggerated here) around an atom results in a ...

Figure 3.14 Looking at van der Waals forces in action. A gecko attached to a...

Figure 3.15 Hydrogen bonding in water ice. The dotted lines show the hydroge...

Figure 3.16 Hydrogen bonding in the molecule DNA. (a) The dotted lines in th...

Figure 3.17 A phase diagram for water. The axes are not drawn to a fixed sca...

Figure 3.18 Ice exposed by the robotic scoop at the Phoenix landing site in ...

Figure 3.19 A simple schematic of a phase diagram for a “typical.” substance...

Figure 3.20 The structure of plasma compared to other states of matter.

Figure 3.21 Electron and neutron degenerate matter. In electron degenerate m...

Figure 3.22 A hypothetical internal structure of a neutron star.

Figure 3.23 A photograph of a black hole. The supermassive black hole is at ...

Figure 3.24 The wavelength and frequency of different types of electromagnet...

Figure 3.25 The origin of emission and absorption spectra. (a) Energy levels...

Chapter 4

Figure 4.1 The six ubiquitous elements of life, CHNOPS. The van der Waals ra...

Figure 4.2 The organic molecule glycine, the simplest amino acid.

Figure 4.3 The 20 common amino acids found in life. The figure shows the dif...

Figure 4.4 Amino acids are zwitterions. At cellular pH, they have the struct...

Figure 4.5 The formation of a peptide bond between two amino acids. This deh...

Figure 4.6 Chirality illustrated with hands and the generic structure for am...

Figure 4.7 Chiral molecules rotate polarized light in particular directions....

Figure 4.8 Different chiralities of life? Gertie the aardvark is a rescued a...

Figure 4.9 The molecular structure of the sugars: glucose, fructose, and rib...

Figure 4.10 Glycosidic bonds allow sugar molecules to be linked together. In...

Figure 4.11 1,4 Glycosidic links between glucose molecules can occur between...

Figure 4.12 The molecular structure of some lipids. Free fatty acids are fou...

Figure 4.13 The structure of DNA and its building blocks. (a) The structure ...

Figure 4.14 The structure of RNA. (a) The schematic structure and bases of a...

Figure 4.15 Water dissolves a range of substances, including salts, sugars, ...

Figure 4.16 The wood frog (Lithobates sylvatica). The frog can tolerate free...

Figure 4.17 Silicon can form extraordinarily complex structures, such as the...

Figure 4.18 Silicate minerals. A variety of silicate structures formed when ...

Figure 4.19 Hybrid silicon–carbon chemistries in life? Silanes can include h...

Figure 4.20 Chemistry in alien solvents. Different functional groups, but an...

Chapter 5

Figure 5.1 Early microbiology. (a) Antonie van Leeuwenhoek, discoverer of mi...

Figure 5.2 Leeuwenhoek's diagrams in the 1670s showing the first drawing of ...

Figure 5.3 The wide variety of prokaryote shapes as seen under a microscope....

Figure 5.4 Amphiphilic molecules such as phospholipids that make up some cel...

Figure 5.5 A simplified diagram showing the structure of a lipid bilayer tha...

Figure 5.6 Gram-negative and Gram-positive cell membranes.

Figure 5.7 A typical structure of peptidoglycan. The pentaglycine cross-link...

Figure 5.8 The structure of archaeal cell membrane lipids compared to bacter...

Figure 5.9 The transcription of DNA into mRNA.

Figure 5.10 The translation of the genetic code. The protein synthesis appar...

Figure 5.11 The structure of t-RNA. The amino acid is attached at the top of...

Figure 5.12 The table of codons of mRNA corresponding to amino acids. The am...

Figure 5.13 A summary of the two steps in reading from DNA to RNA to protein...

Figure 5.14 The replication of DNA. The figure shows some of the diversity o...

Figure 5.15 Plasmids are small circular pieces of DNA. They can be introduce...

Figure 5.16 A typical plant eukaryotic cell with some of its components. The...

Figure 5.17 A schematic illustration of the concept of endosymbiosis. Chloro...

Figure 5.18 The process of mitosis or “binary fission.”

Figure 5.19 The process of meiosis.

Figure 5.20 The major phases of growth in a population of prokaryotes.

Figure 5.21 Microbial movement and flagella. The microbe Salmonella, stained...

Figure 5.22 Tumbleweeds move by rolling, but why don't we see macros...

Figure 5.23 Microbial movements toward nutrients and away from toxins. A pos...

Figure 5.24 Sketch showing different arrangements of flagella. (a) A single ...

Figure 5.25 Slime molds adopt multicellular structures. (a) Slime mold showi...

Figure 5.26 The structure of the Tobacco Mosaic Virus (TMV). The diagram sho...

Chapter 6

Figure 6.1 The variety of different metabolisms in life and some example gro...

Figure 6.2 Adenosine triphosphate (ATP), its structure, and cycle in the cel...

Figure 6.3 A schematic example of an electron transport chain linked to ATP ...

Figure 6.4 The ATP synthase (or F-type ATPase) complex. Schematic showing AT...

Figure 6.5 A general schematic providing an overall summary of the principle...

Figure 6.6 An electron tower showing some examples of half reactions (redox ...

Figure 6.7 The structure of acetyl-CoA and two ancient and important biochem...

Figure 6.8 A summary of the pathways for the break down and generation of en...

Figure 6.9 Pathways for fermentation and just a few of the variety of possib...

Figure 6.10 The reductive acetyl-CoA pathway for the fixation of CO2 into or...

Figure 6.11 The biological methane cycle. The diagram shows some of the majo...

Figure 6.12 White mats of Beggiatoa (center) in the deep oceans. They play a...

Figure 6.13 Microbial iron cycling. (a) An environment in Iceland where iron...

Figure 6.14 Oxygenic photosynthesis. The reaction for oxygenic photosynthesi...

Figure 6.15 The structure of chlorophyll. The side group (shown as x) gives ...

Figure 6.16 The “Z” scheme of oxygenic photosynthesis. The details are descr...

Figure 6.17 Absorption spectra of some photosynthetic pigments.

Figure 6.18 Cyclic phosphorylation in green sulfur bacteria. The electron do...

Figure 6.19 Microbial mats in the Yellowstone National Park include the anox...

Figure 6.20 The structure of rhodopsin illustrated with a computer model. Th...

Figure 6.21 The planetary scale biological nitrogen cycle on Earth. The diag...

Figure 6.22 Microbial mats can contain many layers of microbes. A cross-sect...

Figure 6.23 Zones established through a microbial mat. Different metabolisms...

Figure 6.24 Some examples of predicted Gibbs free energy yields for the Vulc...

Chapter 7

Figure 7.1 A simplified two-dimensional depiction of the limits of life, the...

Figure 7.2 Temperature limits for life. (a) A hydrothermal vent in the Atlan...

Figure 7.3 Habitats for psychrophiles. The ice sheet between Qikiqtarjuaq an...

Figure 7.4 An example of adaptation to low temperatures. The introduction of...

Figure 7.5 Underground astrobiology laboratories. Scientists use a deep unde...

Figure 7.6 Samples of gypsum (hydrated calcium sulfate) with cyanobacteria. ...

Figure 7.7 Life at pH extremes. Left: The acidic Rio Tinto, Spain. Right:...

Figure 7.8 A light micrograph image of the radiation-resistant Deinococcus r...

Figure 7.9 A transmission electron microscope (TEM) image of Cupriavidus met...

Figure 7.10 Types of habitats in and on rocks.

Figure 7.11 A light micrograph image of Chroococcidiopsis, an extreme radiat...

Figure 7.12 Cryptoendolithic microbial communities. (a) Impact-shocked gneis...

Figure 7.13 Laboratories in extreme environments. The International Space St...

Figure 7.14 The limits of the biosphere. Three-dimensional plots of pH, temp...

Figure 7.15 Life in the deep subsurface: a graph showing the logarithmic dec...

Figure 7.16 Schematic diagram of a typical bacterial spore. The exact nature...

Figure 7.17 The brine shrimp, Artemia salina. An example of an extreme-toler...

Figure 7.18 A scanning electron microscope image of a tardigrade (Milnesium ...

Figure 7.19 Are there other biospheres (or “biospaces”) in the Universe with...

Chapter 8

Figure 8.1 Victorian naturalist Charles Darwin, photographed at Down House i...

Figure 8.2 Using resemblances to classify species. For some large organisms,...

Figure 8.3 A phylogenetic tree of life. The diagram shows a variety of group...

Figure 8.4 Phylogenetic trees. (a) A phylogenetic tree of some large mammals...

Figure 8.5 Some groups in phylogenetic trees recognized by cladistics.

Figure 8.6 Analogy or convergent evolution is caused by organisms being expo...

Figure 8.7 Transversions and transitions are just two ways in which mutation...

Figure 8.8 Using DNA sequences to build phylogenetic trees. (a) A variety of...

Figure 8.9 An example phylogenetic tree that is aligned with geological time...

Figure 8.10 Advances in phylogenetics. (a) The first depiction of a hypothet...

Figure 8.11 Phylogenetic bracketing can be used to infer characteristics of ...

Figure 8.12 Using a phylogenetic tree of mitochondrial DNA to infer the evol...

Figure 8.13 Transduction is achieved when a bacteriophage injects DNA into a...

Figure 8.14 Conjugation results in the transfer of genetic material from one...

Figure 8.15 Hypothetical scenarios for alien life. (a) Alien life found on a...

Chapter 9

Figure 9.1 The local galactic cluster showing the Milky Way Galaxy.

Figure 9.2 The events following the Big Bang.

Figure 9.3 Hubble's Law. A simple schematic graph showing the distance–veloc...

Figure 9.4 Schematic showing the proton–proton chain in the cores of low mas...

Figure 9.5 The triple alpha reaction. The numbers of protons and neutrons ar...

Figure 9.6 Schematic of the CNO cycle in high-mass (and intermediate) stars....

Figure 9.7 The structure of high-mass stars. The interior structure of a hig...

Figure 9.8 The cosmic abundance of different elements. The abundance of the ...

Figure 9.9 The Transiting Exoplanet Survey Satellite (TESS). TESS is a space...

Figure 9.10 A Hertzsprung–Russell diagram. The white line shows an approxima...

Figure 9.11 Blackbody radiation curves for an object at different temperatur...

Figure 9.12 Protoplanetary discs. (a) An artist's impression of the early pr...

Figure 9.13 Planets in our Solar System and other examples of key categories...

Figure 9.14 The Galilean moons of Jupiter. From left to right: Io (diameter ...

Figure 9.15 A conceptual illustration of the Oort cloud and Kuiper belt (abo...

Figure 9.16 Comet tails produced by Comet Hale–Bopp, imaged in April 2007....

Figure 9.17 Recovery of a meteorite in Antarctica by members of the United S...

Figure 9.18 The Casas Grandes iron–nickel meteorite with its Widmanst...

Figure 9.19 A section of a pallasite meteorite (Esquel meteorite). The image...

Figure 9.20 Chondrules in a meteorite. Ordinary chondrite NWA 3189 (field of...

Figure 9.21 Some planets appear to move in a retrograde motion or to do a ba...

Figure 9.22 Diagram illustrating Kepler's first two laws: that the Sun is at...

Figure 9.23 Two bodies orbiting their common center of mass.

Chapter 10

Figure 10.1 Clouds of interstellar material and chemistry. Left: The Orion n...

Figure 10.2 The local interstellar clouds through which our Solar System is ...

Figure 10.3 The Dark Cloud B68. On the left the cloud is seen in visible lig...

Figure 10.4 A protoplanetary disc. An ALMA (Atacama Large Millimeter/submill...

Figure 10.5 A carbon-rich star. IRC+10 216 (CW Leo) is a carbon-rich star sh...

Figure 10.6 Shock waves from supernova explosions. Here is shown a multiwave...

Figure 10.7 Interstellar gas phase reactions. Some examples of a wide variet...

Figure 10.8 A typical structure of an interstellar grain showing the core of...

Figure 10.9 Eley–Rideal reactions.

Figure 10.10 Langmuir–Hinshelwood reactions.

Figure 10.11 Hot atom reactions.

Figure 10.12 Polycyclic aromatic hydrocarbons (PAHs). (a) Some examples of P...

Figure 10.13 Apparatus for irradiation and simulation of astrochemical envir...

Figure 10.14 An absorption spectrum for the molecular gas cloud NGC 7538 IRS...

Figure 10.15 An example of the absorption lines across the spectrum (shown a...

Chapter 11

Figure 11.1 The differentiation of Earth.

Figure 11.2 The giant impact hypothesis for the formation of the Moon.

Figure 11.3 Some gases produced by volcanic eruptions would have contributed...

Figure 11.4 Impact basins. Giant impact basins are evident on the Moon as da...

Figure 11.5 Planetary bodies in the inner Solar System preserve a record of ...

Figure 11.6 Late heavy bombardment. A simple schematic graph showing the hig...

Figure 11.7 Ultraviolet (UV) radiation on early Earth. A diagram showing the...

Figure 11.8 Some of the major events in the first billion years of Earth his...

Chapter 12

Figure 12.1 A schematic showing the apparatus used to carry out the Miller–U...

Figure 12.2 A sample of the Murchison meteorite. This carbonaceous meteorite...

Figure 12.3 The structure of α-, β-, γ-, and δ-amino acids....

Figure 12.4 RNA can fold into complex structures. This computer-generated st...

Figure 12.5 A ribozyme. A schematic of the structure of the hammerhead riboz...

Figure 12.6 Compartmentalization of metabolism. Simple metabolisms could hav...

Figure 12.7 A black smoker hydrothermal vent at the Brothers volcano, Kermad...

Figure 12.8 Geothermal origins of life on land? (a) Land-based geothermal (v...

Figure 12.9 The modern-day Pingualuit crater in northern Quebec, Canada, con...

Figure 12.10 A concept for the formation of complex organic molecules in bub...

Chapter 13

Figure 13.1 Volcanic hot springs in Yellowstone National Park. These pools a...

Figure 13.2 Isotopic fractionation illustrated with the two stable carbon is...

Figure 13.3 Isotopic fractionation. An enrichment in the heavier isotope of ...

Figure 13.4 A range of carbon isotope fractionation values for non-biologica...

Figure 13.5 Carbon fractionation through time. Ranges of carbon isotope frac...

Figure 13.6 Some of the first suggested early Earth microfossils from the Ap...

Figure 13.7 A variety of abiotic precipitates produced by chemical reactions...

Figure 13.8 Present-day stromatolites growing in Shark Bay, Australia. Each ...

Figure 13.9 Putative early stromatolites (seen here as wavy rock textures) f...

Figure 13.10 Some biomarkers are distinctive for particular taxa. These ladd...

Figure 13.11 The principle of mass spectrometry (described in the text).

Figure 13.12 A nano-SIMS machine. The vertical structure on the left...

Chapter 14

Figure 14.1 (a) Basalt, an example of a rock containing minerals. (b) Obsidi...

Figure 14.2 The Diamond Synchrotron Source in Oxford (UK). The synchrotron g...

Figure 14.3 An example classification of different types of igneous rocks ac...

Figure 14.4 The names of different types of metamorphic rocks showing the pr...

Figure 14.5 The rock cycle showing the different pathways of rock types and ...

Figure 14.6 The internal structure of Earth.

Figure 14.7 The composition of the crust of Earth compared to the whole Eart...

Figure 14.8 The lack of plate tectonics on Mars has caused the formation of ...

Figure 14.9 A map showing plates and major plate boundaries on Earth.

Figure 14.10 Interactions between plates and the different types of plate bo...

Figure 14.11 The Hawaiian island chain. An example of a hotspot creating vol...

Figure 14.12 A graphical illustration of the decay of a radioisotope over ti...

Figure 14.13 (a) An isochron for a lunar rock. This sample is a dunite, an i...

Figure 14.14 Diagram illustrating some principles of relative age dating of ...

Figure 14.15 Different types of unconformity used in the relative dating of ...

Figure 14.16 An unconformity on Mars (Mount Sharp, Gale Crater) is shown by ...

Figure 14.17 The hierarchies of geological time.

Figure 14.18 The enigmatic creatures and body plans of the Ediacaran.

Figure 14.19 An example Cambrian fossil (Ottoia prolifica), a type of marine...

Figure 14.20 Trilobites. Ubiquitous marine denizens of the Cambrian. Here is...

Figure 14.21 The invasion of land. By the Carboniferous, plants, insects, an...

Figure 14.22 Artists' impressions of some of the reptiles and a mammal of th...

Figure 14.23 An image depicting some of the forms of mammals of the Miocene ...

Figure 14.24 Cenozoic biology. A tool-building ape emerges capable of calcul...

Chapter 15

Figure 15.1 Schematic showing the history of terrestrial atmospheric oxygen ...

Figure 15.2 Minerals whose formation is favored in low oxygen concentrations...

Figure 15.3 A BIF showing the layers of chert (gray/black) interspersed with...

Figure 15.4 Mass-independent fractionation of sulfur over time, showing the ...

Figure 15.5 Cyanobacteria, the organisms responsible for the large-scale inc...

Figure 15.6 Volcanoes are one source of reduced compounds (in gases) that wo...

Figure 15.7 Snowball Earth. Left: An artist's impression of a Snowball Earth...

Figure 15.8 Cap carbonates have been suggested as evidence for high concentr...

Figure 15.9 Cryoconite holes on the Juneau Icefield, Alaska, just one type o...

Figure 15.10 Oxygen free radicals and their biological damage: a schematic s...

Figure 15.11 A model of Anomalocaris, an early Cambrian predator that provid...

Figure 15.12 High concentrations of oxygen linked to insect gigantism? Giant...

Chapter 16

Figure 16.1 A taxidermy specimen of the passenger or wild pigeon.

Figure 16.2 The changing diversity of genera of marine organisms during the ...

Figure 16.3 Dale Russell's intelligent dinosaur shown alongside a model of a...

Figure 16.4 An iridium spike at the Cretaceous–Paleogene boundary in the roc...

Figure 16.5 Evidence for geological changes at the K–Pg boundary associated ...

Figure 16.6 The dinosaurs face an impact winter.

Figure 16.7 The site of the Chicxulub impact crater in Mexico, proposed coll...

Figure 16.8 The Deccan traps (in red) erupted toward the end of the Cretaceo...

Figure 16.9 A correspondence between some (but not all) extinctions (red) an...

Figure 16.10 The remnants of a supernova explosion. This one is SN 1987A, at...

Figure 16.11 The trilobites. Just one group destroyed by the end-Permian ext...

Figure 16.12 A foram showing its calcium carbonate shell. This specimen is a...

Figure 16.13 Lystrosaurus, a pig-sized survivor of the end-Permian extinctio...

Figure 16.14 The frequency and energy of impact events. Energy is given in t...

Figure 16.15 Deflecting asteroids. A concept for deflecting an asteroid on a...

Chapter 17

Figure 17.1 A simplified Venn diagram showing some of the basic requirements...

Figure 17.2 The habitable zone in our Solar System. The dark green zone show...

Figure 17.3 Habitable zones around different stars. (a) The general principl...

Figure 17.4 A diagram showing the temperature and pressure profile t...

Figure 17.5 The carbonate–silicate cycle. (a) One principal mechanism by whi...

Figure 17.6 Multiple factors interact to influence the habitability of Earth...

Figure 17.7 An early model showing the upper and lower value of the obliquit...

Figure 17.8 Environments in the Universe can be split into three types. In m...

Figure 17.9 One model that predicts changes in global mean temperatures over...

Figure 17.10 The galactic habitable zone shown in green in a schematic of th...

Chapter 18

Figure 18.1 A topographic map of Mars obtained with the Mars Orbiter Laser A...

Figure 18.2 Two geological timescales for Mars compared with Earth.

Figure 18.3 Crustal magnetism on Mars. Magnetic stripes in rocks in the anci...

Figure 18.4 A schematic of the Maxwell–Boltzmann distribution of speeds in g...

Figure 18.5 Early Mariner 9 image of Mars taken in 1971. The towering peaks ...

Figure 18.6 The NASA Opportunity rover. A simulated view of the rover at End...

Figure 18.7 Pale silica deposits on Mars revealed by the wheels of the Spiri...

Figure 18.8 The European Mars Express spacecraft at Mars.

Figure 18.9 False color image of the edge of Jezero crater (49 km in diamete...

Figure 18.10 Panoramic view around the Phoenix lander.

Figure 18.11 The NASA Curiosity rover on Mars. A selfie taken during a Marti...

Figure 18.12 Artist's impression of the ISRO Mangalyaan mission at Mars.

Figure 18.13 The NASA InSight lander on Mars before deployment of the seismo...

Figure 18.14 Geological diversity in the Nili Fossae, Mars. Image of part of...

Figure 18.15 Ancient sediments on Mars. This evenly layered rock photographe...

Figure 18.16 An example of cross-bedding on Mars. It results from water pass...

Figure 18.17 Examples of catastrophic outflow channels on Mars imaged by the...

Figure 18.18 Hydrogen in the surface of Mars detected by gamma ray spectrosc...

Figure 18.19 Recent small craters on Mars reveal subsurface ice that is obse...

Figure 18.20 Evidence for the stability of liquid water on present-day Mars?...

Figure 18.21 Evidence for a subglacial lake on Mars. Radar tracks on the Pla...

Figure 18.22 Martian drill holes. By drilling into Martian sediments and exa...

Figure 18.23 Gypsum (hydrated CaSO4) veins on Mars imaged by the NASA Curios...

Figure 18.24 Rocks on Mars have many of the trace elements required for life...

Figure 18.25 Martian habitability trajectories. The figure shows some differ...

Figure 18.26 A Mars simulation chamber used to re-create conditions in the l...

Figure 18.27 One of the Viking landers showing its scoop in operation in a m...

Figure 18.28 The abundance of gases found trapped in the glasses of the Mart...

Figure 18.29 ALH84001, a Martian meteorite.

Figure 18.30 Putative microfossils in ALH84001. The putative microfossil sha...

Figure 18.31 Mars analog environments. Scientists investigating life living ...

Figure 18.32 Mars analog environments. Iceland is an environment dominated b...

Figure 18.33 Mars analog environments are used for scientific investigations...

Figure 18.34 Are planets biogeographical islands? A schematic showing the di...

Figure 18.35 A light gas gun can be used to simulate asteroid impact by acce...

Figure 18.36 The EXPOSE facility built for the European Space Agency (ESA). ...

Figure 18.37 The FOTON spacecraft returns to Earth in the steppes of Kazakhs...

Chapter 19

Figure 19.1 Saturn's rocky moon, Pandora, about 100 km in length. It is repr...

Figure 19.2 Galileo Galilei, discoverer of four moons orbiting Jupiter.

Figure 19.3 Left: Europa, showing its characteristics lines across the surfa...

Figure 19.4 The surface of Europa showing subdued regions and domes. This ar...

Figure 19.5 Conamara Chaos, a region of broken chaotic terrain on Europa. Th...

Figure 19.6 A subsurface ocean in Europa a hypothetical schematic showing th...

Figure 19.7 The internal structure of Ganymede. Left: A possible complex str...

Figure 19.8 Callisto.

Figure 19.9 Io.

Figure 19.10 The reflective surface of Enceladus. The blue tiger stripes are...

Figure 19.11 The plumes of Enceladus.

Figure 19.12 One model for liquid water formation within the ice crust of En...

Figure 19.13 Tidal heating in Enceladus. The tiger stripes of Enceladus (lef...

Figure 19.14 Plumes of water erupted from Enceladus (inset), their compositi...

Figure 19.15 Titan's haze. Titan in the visible wavelength range imaged by t...

Figure 19.16 (a) Surface features of Titan. On the left is a mosaic of nine ...

Figure 19.17 Kraken Mare, a large northern lake on Titan shown in blue (fals...

Figure 19.18 Titan's surface, as imaged by the Huygens probe. The large boul...

Figure 19.19 Changing lake levels (imaged in red blocks and shown as colored...

Figure 19.20 A schematic showing the methane and hydrocarbon cycle on Titan.

Figure 19.21 A schematic showing the structure of Titan's atmosphere compare...

Figure 19.22 A proposed structure of Titan.

Figure 19.23 A putative internal structure of Ceres. The schematic shows, fr...

Figure 19.24 Geological features of Ceres. Some interesting geological featu...

Figure 19.25 Triton's surface, imaged by Voyager 2. The black ovals on the s...

Figure 19.26 Pluto, a location of active icy geological processes. This imag...

Figure 19.27 An annotated image of the plains of Pluto showing what appear t...

Figure 19.28 A Viking lander being heat-sterilized prior to being dispatched...

Chapter 20

Figure 20.1 An artist's impression of 51 Pegasi b, the first exoplanet to be...

Figure 20.2 The transit method of exoplanet detection. (a) Schematic showing...

Figure 20.3 The Doppler method of exoplanet detection. (a) The Doppler metho...

Figure 20.4 Gravitational lensing showing the effect of a planet on the imag...

Figure 20.5 Direct imaging of three planets. Three exoplanets orbiting a you...

Figure 20.6 How nulling interferometry works. Two telescopes are set up so t...

Figure 20.7 Diagrams illustrating the diversity of exoplanet properties. Pla...

Figure 20.8 An artist's impression of a Hot Neptune.

Figure 20.9 An artist's impression of an ocean world with two satellites....

Figure 20.10 An artist impression of a rocky world orbiting another star....

Figure 20.11 Schematic showing the size of Kepler-186 f, the first proposed ...

Figure 20.12 The Kepler 186 and 452 systems compared to our own Solar System...

Figure 20.13 Rocky planets of the TRAPPIST-1 system. On the left is shown a ...

Figure 20.14 At the top, an artist's impression of Gliese 667 Cb with two st...

Figure 20.15 Quadruple star systems as homes for exoplanets. Kepler 64b is a...

Figure 20.16 Schematic showing the size of the HAT-P-1 puffy planet compared...

Figure 20.17 An artist's impression of a carbon planet. Its darkness is a pr...

Figure 20.18 The absorption spectrum of Earth. At the top, the radiation rec...

Figure 20.19 Computer models of Earth's light spectrum: a synthetic ultravio...

Figure 20.20 The absorption spectra of Venus, Mars, and Earth from the visib...

Figure 20.21 Concentrations in parts per billion (ppb) of N2O in the atmosph...

Figure 20.22 Simple schematic reflectance spectrum showing the vegetation re...

Figure 20.23 Different biological spectral edges. Some example organisms pos...

Figure 20.24 Artist impression of a coronagraph (the star-shaped object in t...

Chapter 21

Figure 21.1 The Search for Extraterrestrial Intelligence (SETI) seeks to fin...

Figure 21.2 Frank Drake, a pioneer in SETI searches and originator of Projec...

Figure 21.3 The hydrogen and hydroxyl frequencies provide one location in th...

Figure 21.4 The Pioneer spacecraft plaques.

Figure 21.5 The Voyager record.

Figure 21.6 Communicating with Extraterrestrial Intelligence. Above: The Are...

Figure 21.7 The search for rocky extrasolar planets allows us to constrain f...

Figure 21.8 Are civilizations destined to destroy themselves?

Figure 21.9 Denizens of Mars attack Earth in HG Wells' War of the Worlds. An...

Figure 21.10 Earth as a target of alien observation. Perhaps, as we observe ...

Figure 21.11 Who should coordinate response to alien contact? The United Nat...

Chapter 22

Figure 22.1 A simple family phylogenetic tree – the emergence of the Hominid...

Figure 22.2 Principal migratory routes of modern humans showing some estimat...

Figure 22.3 A Neanderthal surveys its surroundings.

Figure 22.4 Tool-building ability. One of the distinguishing traits of human...

Figure 22.5 Porcelain Basin, Yellowstone National Park. The park is the loca...

Figure 22.6 The rise in the human population poses one threat to the sustain...

Figure 22.7 The Montreal Convention. The convention banned the use of chloro...

Figure 22.8 The rise in CO2 in the atmosphere measured at Mauna Loa, Hawaii,...

Figure 22.9 A station on the Moon.

Figure 22.10 The European Space Agency's MELiSSA life support system. The fi...

Figure 22.11 The Apollo Portable Life Support System. This system provided o...

Figure 22.12 A human outpost on Mars.

Figure 22.13 The exploration of Mars.

Figure 22.14 Explorers reach the summit of Olympus Mons, the highest peak on...

Figure 22.15 A mining outpost on an asteroid.

Figure 22.16 Outer Solar System stations. The geological stability and relat...

Figure 22.17 A toroidal spaceship houses many thousands of humans.

Figure 22.18 The interior of a large-scale spaceship houses entire communiti...

Figure 22.19 Becoming a multiplanet species. (a) A civilization located on o...

Figure 22.20 A dramatic depiction of dinosaur extinction. Unless we build as...

Figure 22.21 Can viewing Earth from a distance and seeing its smallness agai...

Figure 22.22 Human civilization became an interstellar spacefaring civilizat...

Guide

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Astrobiology

Understanding Life in the Universe

 

Second Edition

 

CHARLES S. COCKELL

School of Physics and Astronomy, University of Edinburgh, UK

 

 

 

 

 

 

 

 

This edition first published 2020

© 2020 John Wiley and Sons Ltd

Edition History

John Wiley & Sons Ltd (1e, 2015)

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Library of Congress Cataloging-in-Publication Data

Names: Cockell, Charles, author.

Title: Astrobiology : understanding life in the universe / Charles S. Cockell, School of Physics and Astronomy, University of Edinburgh, UK.

Description: 2nd edition. | Hoboken : Wiley-Blackwell, 2020. | Includes bibliographical references and index.

Identifiers: LCCN 2019051498 (print) | LCCN 2019051499 (ebook) | ISBN 9781119550358 (paperback) | ISBN 9781119550303 (adobe pdf) | ISBN 9781119550396 (epub)

Subjects: LCSH: Exobiology–Textbooks. | LCGFT: Textbooks.

Classification: LCC QH326 .C63 2020 (print) | LCC QH326 (ebook) | DDC 576.8/39–dc23

LC record available at https://lccn.loc.gov/2019051498

LC ebook record available at https://lccn.loc.gov/2019051499

Cover Design: Wiley

Cover Image: © JPL/Space Science Institute/NASA

Acknowledgments

This textbook has been enormous fun to write and a pleasure to update. It could not have been done without help from many people. I am grateful to colleagues for reading chapters and providing general and specific feedback on their content, readability, and style. I am particularly grateful to those whom I acknowledged in the first edition of the textbook, the edition from which this version has been built. I would also like to acknowledge the thoughtful and very helpful review comments of Ania Losiak, Rosa Santomartino, Annemiek Waajen, Stewart Gault, Rosie Cane, Peter Higgins, and Kate Haigh.

I would like to give special thanks to all the undergraduate students of the Astrobiology course at the University of Edinburgh (PHYS08051) that I have taught since 2013. It is their views, perspectives, and insights that led to the structure of this textbook when it was first written, and that have improved the content and structure in this second edition. Some subjects seem important, but turn out to be less useful as a way to teach concepts when exposed to the enquiring eyes of undergraduates. Other information seems tangential, but something about it makes it useful to get across certain ideas and knowledge. So I am immensely grateful to all the undergraduates who have patiently sat in lectures year after year and have honed my knowledge of what works and what doesn't. I would like to thank the University of Edinburgh and the School of Physics and Astronomy for the opportunity to teach astrobiology.

Further refinements in the content and level of the book have been made based on the feedback and opinions of over 150 000 students who have taken part in our “Astrobiology and the Search for Extraterrestrial Life” Massive Open Online Course (MOOC) since it was offered online in 2012. I have not had direct face-to-face teaching contact with them, but in the online forums, their views on the teaching material have been valuable.

I hope that other students interested in astrobiology, and indeed anyone else interested in the subject, can gain the vicarious benefit of the collected experience of these students through this textbook.

Some of the images in the book were kindly provided by friends and colleagues, including Steve Benner, Hailiang Dong, Ralf Kaiser, Jonathan Clarke, and Victor Tejfel. I would like to thank the journal Astrobiology for permission to reproduce images.

Any errors in the textbook are entirely my responsibility. If you see any, or disagree with any statements, please do get in contact.

I would very much like to thank the team at Wiley-Blackwell, particularly Sonali Melwani, for seeing this book through into the second edition. It has been a pleasure to work with Wiley-Blackwell.

Charles S. Cockell

About the Companion Website

This book is accompanied by a companion website:

www.wiley.com/go/cockell/astrobiology

The website includes:

A complete astrobiology lecture course comprising slide sets for each of the chapters.

Exam questions related to the chapters.

Astrobiology Periodic Table

1Astrobiology

Learning Outcomes

Understand that astrobiology is concerned with the origin, evolution, and distribution of life in the Universe. It investigates life in its cosmic context.

Understand some of the detailed scientific questions that underpin astrobiology's main lines of enquiry.

Know about some aspects of the history of astrobiology and how it emerged as a field.

1.1 Introductory Remarks

If you've ever wondered about some of the most fascinating questions in science, such as how life originated, whether it could exist elsewhere, and how life has managed to evolve and persist on our planet for over three and a half billion years, then you've opened the right book.

Astrobiology is a remarkably diverse subject whose main objective is to investigate and understand the phenomenon of life in its cosmic context (Figure 1.1). Astrobiology might be said to address at least four large-scale questions:

How did life originate and diversify on Earth?

How does life co-evolve with a planet?

Does life exist beyond Earth?

What is the future of life on Earth and its capacity to move beyond the home planet?

Figure 1.1 Astrobiology seeks to understand the phenomenon of life in its cosmic context. This “ultra-deep field” view imaged by the Hubble Space Telescope includes nearly 10 000 galaxies across the observable Universe in both visible and near infrared light. The smallest, reddest galaxies are among the youngest, in existence when the Universe was just 800 million years old. How does life fit into this grand cosmic perspective?