Astrobiology : An Introduction book cover
1st Edition

An Introduction

ISBN 9781439875766
Published November 24, 2014 by CRC Press
472 Pages - 145 B/W Illustrations

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Book Description

Astrobiology is a multidisciplinary pursuit that in various guises encompasses astronomy, chemistry, planetary and Earth sciences, and biology. It relies on mathematical, statistical, and computer modeling for theory, and space science, engineering, and computing to implement observational and experimental work. Consequently, when studying astrobiology, a broad scientific canvas is needed. For example, it is now clear that the Earth operates as a system; it is no longer appropriate to think in terms of geology, oceans, atmosphere, and life as being separate.

Reflecting this multiscience approach, Astrobiology: An Introduction:

  • Covers topics such as stellar evolution, cosmic chemistry, planet formation, habitable zones, terrestrial biochemistry, and exoplanetary systems
  • Discusses the origin, evolution, distribution, and future of life in the universe in an accessible manner, sparing calculus, curly arrow chemistry, and modeling details
  • Contains problems and worked examples, and includes a solutions manual with qualifying course adoption

Astrobiology: An Introduction provides a full introduction to astrobiology suitable for university students at all levels.

Table of Contents





Origin of the Elements

Elements for Life

The Universe Started from a Hot and Dense State

Abundances of Primordial Elements Are Predicted by the Big Bang Hypothesis

The Message of Light

Atoms and Molecules Process Electromagnetic Radiation

Electronic Transitions Are Quantized

Energy Levels Govern Electronic Transitions in the Hydrogen Atom

Spectrographs Are Used to Capture Spectra

Stellar Spectra Encode Temperature and Elemental Abundances

Stellar Evolution

The Properties of Main Sequence Stars Are Determined by Their Masses

Stars Form by the Collapse of Giant Molecular Clouds

Protostars Contract Down Onto the Main Sequence

Main Sequence Stars Fuse Hydrogen to Helium

Many Low Mass Stars Become Red Giants

High Mass Stars Make High Mass Elements

The Chemistry of Space

From Elements to Molecules

Astrochemical Environments

Cool Stars Have Molecular Absorption Lines

The Interstellar Medium Is Extremely Tenuous

The ISM Contains Dust Grains

AGB Stars Have Either Oxygen- or Carbon-Rich Atmospheres

Doing Chemistry in Space

Different Chemistry Operates in Dense Clouds and Diffuse Clouds

Molecular Spectroscopy

Molecules Are Detected Mostly by Vibrational and Rotational Spectra

Building Molecules

Molecules in the ISM

Reaction Mechanisms

Chemical Networks

Dust Grain Surfaces Catalyze Synthesis of Hydrogen Molecules

Chemical Species Can Trace ISM Conditions and Processes

Habitable Earth

Earth in Context

There Are Eight Major Planets

The Planets Were Condensed from a Spinning Disc

The Solar System Contains Numerous Small Bodies

What Is a Planet?

Habitability Is an Attribute of the Entire Earth System

The Structure and Composition of the Solid Earth

The Chondritic Earth Model Provides a First Approximation to Its Bulk Composition

Seismology Provides a Picture of the Earth’s Interior

What Makes Earth Habitable?

Temperature at the Earth’s Surface Is Largely Determined by the Sun

Liquid Water Exists on the Earth’s Surface

Earth Is in a Stable Orbit in the Habitable Zone

Earth’s Dense Atmosphere Contributes to Habitability

A Global Magnetic Field May Be Required for Habitability

Earth Seems Unique in Having Plate Tectonics

Plate Tectonics Depends on a Weak Mantle Layer

New Ocean Crust Is Made at Constructive Plate Boundaries

Ocean Crust Is Destroyed at Destructive Plate Boundaries

Hot Spot Volcanism: Evidence for Mantle Convection?

Plate Tectonics Is Self-Regulating

Plate Tectonics May Be Required for Habitability

Plate Tectonics Seems Not to Operate on Mars or Venus

Building the Solar System

Planet Formation Is Contingent

Planets Formed by Accretion from the Solar Nebula

The Solar Nebula Was a Dynamic Environment

The Solar Nebula Formed a Spinning Disc

Planet and Star Formation Occur Together

Condensation of Solids from the Solar Nebula Depended on Temperature

Accretion Involves Several Distinct Mechanisms

Heat Sources Drive Differentiation

Differentiation Redistributes Elements

Gas Giants Must Have Assembled Within a Few Million Years

Accretion of Terrestrial Planets Took Tens of Millions of Years

The Solar System Started with a Bang

26Mg Traces the Original 26Al

Did the Decay of 26Al Make Life on Earth Possible?

Dating Events in the Early Solar System Relies on Radioactive Isotopes

Radiometric Dating Relies on the Exponential Decay of Radioisotopes

Radiometric Dating Uses Isochron Plots

Planetary Migration Is Required to Resolve Several Paradoxes

Theories of Planetary Migration Have Been Derived

Some Features of Solar System Architecture Have Been Hard to Explain

The Nice Model Accounts for Solar System Architecture by Planetary Migration

Early Earth

Assembly of the Earth Can Be Modeled

To First Approximation Earth Grew at a Decreasing Exponential Rate

Accretion Was Probably Heterogeneous

Early Earth Was Shaped by a Moon-Forming Impact

The Moon-Forming Impact Is Supported by Theory and Geochemistry

The Timing of the Moon-Forming Impact Is Poorly Constrained

Tidal Forces Drove Evolution of the Earth–Moon System

The Early Hadean Was Hot

Earth’s Postimpact Atmosphere Was Largely Rock Vapor

A Magma Ocean Remained After the Moon-Forming Impact

The Hadean Mantle, Atmosphere, and Oceans Could Have Coevolved

A Dry Accreting Earth Would Be Hot During the Hadean

Late Events Modified the Composition of the Earth

Earth’s Mantle and Crust Has an Excess of Siderophile Elements

Core Separation Happened at High Pressure and Temperature

Siderophile Elements Were Likely Delivered by a Late Veneer

The Mantle Has Become More Oxidized with Time

How Did the Terrestrial Planets Acquire Water?

The Water Inventory of the Earth Is Not Well Known

Did Terrestrial Planets Accrete Dry?

Did Terrestrial Planets Accrete Wet?

Volatile Delivery Could Have Occurred Late

The Temperature of the Late Hadean and Archaean Are Not Well Constrained

Geological Clues Suggest Early Earth Was Warm Rather Than Hot

When Did the First Oceans Form?

Plate Tectonics on Early Earth

When Did Plate Tectonics Start on Earth?

Plate Tectonics May Not Have Operated in the Hadean

What Was the Nature of Early Plate Tectonics?

Earth’s Atmosphere Has Changed over Time

Earth’s Atmosphere May Come from Two Sources

The Oxidation State of the Atmosphere Has Altered

Nitrogen May Be Derived from Ammonia

The Faint Young Sun Paradox

Properties of Life

Can Life Be Defined?

Life Is a Complex, Self-Organizing, Adaptive Chemical System

The Chemistry of Life Is Far from Equilibrium

Life Requires an Energy Source

Living Systems Are Capable of Self-Replication

Life Exhibits Darwinian Evolution

How Useful Are These Criteria for Detecting Life?

Are There Universal Chemical Requirements for All Life?

No Element Is More Versatile in Its Chemistry than Carbon

Water as a Universal Solvent

Terrestrial Biochemistry

Building Blocks for Life

Polymeric Macromolecules

All Life on Earth Consists of Cells

Information Flow in Cells

All Life on Earth Has One of Two Basic Cell Architectures

Gene Transfer Can Occur Vertically or Horizontally

All Life on Earth Falls into Three Domains

DNA Is the Universal Replicator

All Life on Earth Uses DNA

DNA Replication Was Deduced from Theory

DNA Acts as a Template

Metabolism Matches Lifestyle

Living Systems Enhance Reaction Kinetics

Life on Earth Has Three Metabolic Requirements

Cells Harness Free Energy

Respiration Requires an Exogenous Electron Acceptor

Most Carbon Oxidation Happens in the Krebs Cycle

Electron Chains "Quantize" Free Energy Availability

ΔG°′ of Redox Reactions Can Be Calculated

Proton Gradients Are the Core of Terrestrial Metabolism

Anerobic Respiration Uses Electron Acceptors Other Than Oxygen

Fermentation Uses an Endogenous Electron Acceptor

Phototrophs Harvest Sunlight

Not All Photosynthesis Produces Oxygen

Oxygenic Photosynthesis Produces ATP and Reducing Power

Prokaryotes Live in the Crust

Crust Provides an Ecologic Niche

Chemolithotrophs "Eat" Rock

Origin of Life

When Did Life Originate?

When Did Earth Become Cool Enough for Life?

Evidence for Early Life

Precambrian Life Was Dominated by Stromatolites

Building the Molecules of Life

Where Did Prebiotic Synthesis Happen?

Did Replication Precede Metabolism?

Did Metabolism Emerge Before Replication?

How Did Life Originate?

What Were the First Organisms?

What Was the Last Universal Common Ancestor?

Hydrothermal Vents Are Prime Candidates for Genesis

Early Life

A Methane Greenhouse

A Shift from CO2 to CH4 Greenhouse Happened in the Late Archaean

An Organic Haze Would Form as CH4 Levels Rose

The Great Oxidation Event

The Oxygen Source Was Photosynthesis

Evidence for the GOE is Geochemical

Whiffs of Oxygen Preceded the GOE

Glaciations Coincided with the GOE

The "Boring Billion"

O2 Levels Plummeted After the GOE

The Canfield Ocean Is Anoxic and Sulfidic

The Neoproterozoic Oxidation Event

The Emergence of Life

Methanogenesis and Sulfate Reduction Were Intertwined

Nitrogen Fixation Probably Evolved Very Early

Genome Expansion Occurred in the Archaean

When Did Oxygenic Photosynthesis Start?

Eukaryotes: Complex Life

When Did Eukaryotes Appear?

Eukaryotes Are Archaeon–Bacteria Chimeras

The Hydrogen Hypothesis Explains Endosymbiosis

Eukaryotes Inherited Bacterial Lipids

Eukaryotes Have Huge Advantages Over Prokaryotes

Mitochondria Are Advantageous for Energetics

Large Size Is Advantageous for Eukaryotes

The Fate of Life on Earth

Earth Will Be Habitable for Another 1.5 Billion Years


Martian Romance

Mariner Missions Reveal a Cold Arid World

Martian Geology

Mars Is a Planetary Embryo

Mars Has Two Very Different Hemispheres

Spectrometry Reveals the Nature of Planetary Surfaces

The Martian Crust Is Mostly Basalt

Water Ice Is Abundant on Mars

Mars Has Substantial Frozen Water

Water Has Flowed on Mars

Mars Has Numerous Fluvial Features

Mars Exploration Rovers Have Searched for Signs of Liquid Water

Global Geological Markers Can Reveal How Long Mars Was Wet

Mars Has Experienced Three Climates


Liquid Water Cannot Exist at the Martian Surface Today

Detection of Methane in the Martian Atmosphere Is Dubious

Atmosphere of Early Mars

Was Mars Episodically Warm and Wet?

Mars and Life

The Viking Experiments Were Designed to Detect Life

Does ALH84001 Harbor Evidence of Life?

Martian Life Could Be Based on Iron and Sulfur Metabolism

Icy Worlds

Life Might Exist Beyond the Conventional Habitable Zone


Titan Has a Dense Atmosphere

Atmospheric Methane Must Be Continually Regenerated

Organic Chemistry Occurs in Titan’s Atmosphere

Could There Be Life on Titan?


Enceladus Has Been Resurfaced Multiple Times

Enceladus Cryovolcanic Plumes Contain Water Vapor

What Heats Enceladus Now?


Europa Is a Differentiated World

There Is Good Evidence for a Europan Ocean

How Thick Is the Europan Crust?

The Europan Surface Is Chemically Altered

What Is the Astrobiological Potential of Europa?

Detecting Exoplanets

Exoplanet Bonanza

The First Exoplanets Were Found by Timing Pulsars

The First Exoplanet Around a Main Sequence Star Was Discovered in 1995

Some Exoplanets Can Be Imaged Directly

Planets Are Extremely Dim Compared to Their Host Stars

Coronagraphs Create Artificial Eclipses

Nulling Interferometry Cuts Out Starlight

Direct Imaging Reveals High Mass Planets

Astrometry Detects Binary Systems by Stellar "Wobble"

The Radial Velocity Method Uses the Doppler Effect

Defining the Radial Velocity

Finding the Period and Semi-Major Axis of an Exoplanet’s Orbit

The RV Method Provides a Lower Bound on Planetary Mass

The RV Method Is Biased to Detect Massive Planets with Short Periods

Exoplanets Are Revealed When They Transit Their Star

Exoplanet Transits Dim Starlight

The Transit Method Allows Several Parameters to Be Deduced

Transit Timing Variation Uncovers Multiple and Circumbinary Exoplanets

Transits Can Potentially Detect Earth-Mass Planets

Most Transit Detections Have Been Made from Space

Gravitational Lensing Can Unveil Exoplanets

Gravitational Microlensing Events Are Short-Lived

Microlensing Yields Information About Exoplanet Systems

There Are Both Pros and Cons to Lensing

Detection Methods Are Biased

Survey Statistics Can Estimate What We Cannot Detect

Exoplanetary Systems

Surveys Probe Exoplanet Properties

Exoplanet Diversity Is Large

Exoplanets Are Classified According to Their Size

Hot Jupiters Were Discovered Early

Small Exoplanets Are Commonest

Exoplanet Composition Can Sometimes Be Deduced

Exoplanet Temperature Can Be Estimated

Exoplanet Host Star Properties

Metal-Rich Stars Are More Likely to Host Gas Giants

Did Terrestrial Planets Form 11 Billion Years Ago?

Most Stars with Planets Have Low Lithium Abundance

Habitable Exoplanets

η⊕ Is the Proportion of Stars with Habitable Planets

An Earth-Sized Planet in the Habitable Zone Has Been Discovered

How to Define a Habitable Zone

η⊕ Has Been Derived from Kepler Data

Habitable Planets Around M-Dwarfs?

Habitability of Planets and Eccentricity Orbits

Planets Exist in Binary Systems

The Galactic and Habitability

The Milky Way Is a Spiral Galaxy

Galactic Chemistry Influences Habitability

The Galaxy Has a Habitable Zone

Are There Habitable Planets in Clusters?


Prospecting for Life

Rare Earth versus the Principle of Mediocrity

Is an Early Origin a Guide to the Probability of Life?

Life May Be Rare or Common in the Galaxy

Several Hard Steps Could Be Needed for Intelligent Observers to Emerge

What Are the Hard Steps?

Is Life Seeded from Space?

Survival of Ancient Bacteria Makes Panspermia Plausible

Life May Be Uncommon Despite Panspermia

Radiation Is a Major Hazard

Can Micro-Organisms Survive Lithopanspermia?

Metrics for Extraterrestrials

Is the Drake Equation More than a Guess?

Alternatives to the Drake Equation Have Been Developed

SETI and the Fermi Paradox

Radio SETI

Optical SETI

How Far Away Would Passive Radiation Reveal Our Presence?

Where Is Everybody?



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Alan Longstaff originally trained as a biochemist and, after a senior lectureship in the Biosciences Department at the University of Hertfordshire, he became a university student once again to study astronomy and planetary science. He now divides his time between teaching and writing. Since 2003, he has worked part-time as an astronomy tutor and planetarium presenter for The Royal Observatory, Greenwich, and held part-time teaching posts at Queen Mary University of London, Waldegrave Science School for Girls, and the Open University. He has lectured to astronomical and geological societies, co/authored several textbooks, and is a regular contributor to Astronomy Now.

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