From Dust To Life: The Origin and Evolution of Our Solar System - Hardcover

Chambers, John; Mitton, Jacqueline

Hardcover

ISBN 10: 0691145229 ISBN 13: 9780691145228

Publisher: Princeton University Press, 2013

Synopsis

The birth and evolution of our solar system is a tantalizing mystery that may one day provide answers to the question of human origins. This book tells the remarkable story of how the celestial objects that make up the solar system arose from common beginnings billions of years ago, and how scientists and philosophers have sought to unravel this mystery down through the centuries, piecing together the clues that enabled them to deduce the solar system's layout, its age, and the most likely way it formed. Drawing on the history of astronomy and the latest findings in astrophysics and the planetary sciences, John Chambers and Jacqueline Mitton offer the most up-to-date and authoritative treatment of the subject available. They examine how the evolving universe set the stage for the appearance of our Sun, and how the nebulous cloud of gas and dust that accompanied the young Sun eventually became the planets, comets, moons, and asteroids that exist today. They explore how each of the planets acquired its unique characteristics, why some are rocky and others gaseous, and why one planet in particular--our Earth--provided an almost perfect haven for the emergence of life. From Dust to Life is a must-read for anyone who desires to know more about how the solar system came to be. This enticing book takes readers to the very frontiers of modern research, engaging with the latest controversies and debates. It reveals how ongoing discoveries of far-distant extrasolar planets and planetary systems are transforming our understanding of our own solar system's astonishing history and its possible fate.

About this title

About the Author

John Chambers is a planetary scientist in the Department of Terrestrial Magnetism at the Carnegie Institution for Science. Jacqueline Mitton is a writer, editor, and media consultant in astronomy. Her books include Titan Unveiled: Saturn's Mysterious Moon Explored (Princeton).

From the Back Cover

"As an astrophysicist credentialed in the days before the space era, I figured reading another book on the solar system would be a big yawn. Surprise! I couldn't have been more wrong! Here is an eye-opening up-to-date reconnaissance of what's in our part of the universe and how it has evolved. Along the way, this arresting account reveals how unique our planetary system really is."--Owen Gingerich, Harvard-Smithsonian Center for Astrophysics

"The origin of our solar system is among the hottest and most fascinating research topics in all of planetary science and astronomy. Chambers and Mitton have produced a compelling and up-to-date survey of this field that reads quickly and authoritatively and leaves no stone unturned in surveying the landscape of this vast and rich topic. I recommend it with gusto!"--Alan Stern, Southwest Research Institute

"John Chambers is one of the world's leading authorities on the origin of the solar system, and here, together with Jacqueline Mitton, provides an engaging summary of the new discoveries for a wider audience. This book is unquestionably the most up-to-date and authoritative popular presentation of current thinking on the subject."--Philip J. Armitage, author of Astrophysics of Planet Formation

"There is no other book out there that discusses the origin of the solar system in this much detail yet is still accessible to nonscientists. Chambers and Mitton do an excellent job of keeping abreast of the notable discoveries in recent years."--Jane Luu, Massachusetts Institute of Technology

"An exciting and rewarding read from cover to cover. You come away feeling well-served and well-educated. This is a great book."--Erik Asphaug, University of California, Santa Cruz

From the Inside Flap

"As an astrophysicist credentialed in the days before the space era, I figured reading another book on the solar system would be a big yawn. Surprise! I couldn't have been more wrong! Here is an eye-opening up-to-date reconnaissance of what's in our part of the universe and how it has evolved. Along the way, this arresting account reveals how unique our planetary system really is."--Owen Gingerich, Harvard-Smithsonian Center for Astrophysics

"The origin of our solar system is among the hottest and most fascinating research topics in all of planetary science and astronomy. Chambers and Mitton have produced a compelling and up-to-date survey of this field that reads quickly and authoritatively and leaves no stone unturned in surveying the landscape of this vast and rich topic. I recommend it with gusto!"--Alan Stern, Southwest Research Institute

"John Chambers is one of the world's leading authorities on the origin of the solar system, and here, together with Jacqueline Mitton, provides an engaging summary of the new discoveries for a wider audience. This book is unquestionably the most up-to-date and authoritative popular presentation of current thinking on the subject."--Philip J. Armitage, author ofAstrophysics of Planet Formation

"There is no other book out there that discusses the origin of the solar system in this much detail yet is still accessible to nonscientists. Chambers and Mitton do an excellent job of keeping abreast of the notable discoveries in recent years."--Jane Luu, Massachusetts Institute of Technology

"An exciting and rewarding read from cover to cover. You come away feeling well-served and well-educated. This is a great book."--Erik Asphaug, University of California, Santa Cruz

Excerpt. © Reprinted by permission. All rights reserved.

FROM DUST TO LIFE

THE ORIGIN AND EVOLUTION OF OUR SOLAR SYSTEM

By JOHN CHAMBERS, JACQUELINE MITTON

PRINCETON UNIVERSITY PRESS

Copyright © 2014 John Chambers and Jacqueline Mitton
All rights reserved.

ISBN: 978-0-691-14522-8

Contents

List of Illustrations......................................................
xi
Preface....................................................................
xv
ONE Cosmic Archaeology.....................................................
1
TWO Discovering the Solar System...........................................
19
THREE An Evolving Solar System.............................................
43
FOUR The Question of Timing................................................
56
FIVE Meteorites............................................................
75
SIX Cosmic Chemistry.......................................................
92
SEVEN A Star Is Born.......................................................
108
EIGHT Nursery for Planets..................................................
123
NINE Worlds of Rock and Metal..............................................
140
TEN the Making of the Moon.................................................
168
ELEVEN Earth, Cradle of Life...............................................
186
TWELVE Worlds of Gas and Ice...............................................
205
THIRTEEN What Happened to the Asteroid Belt?...............................
225
FOURTEEN The Outermost Solar System........................................
242
FIFTEEN Epilogue: Paradigms, Problems, and Predictions.....................
263
Glossary...................................................................
277
Sources and Further Reading................................................
291
Index......................................................................
293

CHAPTER 1

COSMIC ARCHAEOLOGY

A FASCINATION WITH THE PAST

The temple at Karnak on the River Nile is one of the most magnificentmonuments to survive from ancient Egypt. Construction of the vasttemple complex began 3,000 years ago, and 30 different pharaohs developedand extended the site for a millennium afterward. Everywhereat Karnak, the stone walls and columns of the temple precincts are inscribedwith historical texts, prayers, and accounts of religious rituals.Today, guides routinely explain to tourists the meaning of the symbolsincised in stone and the significance of this immense monument. Yetfor 1,500 years no one in the world could make sense of the writing, andmuch of ancient Egyptian civilization was a mystery.

The inscriptions at Karnak are composed of hieroglyphics, one of theoldest written languages in the world. The ancient Egyptians used thispictorial script for formal and sacred documents, but its use declinedafter Egypt became a Roman province in 30 BC. When Egypt becameChristian in the 4th century AD, all memory of hieroglyphics was lost.Over the following centuries, scholars puzzled over the meaning of hieroglyphsbut never managed to decode them.

In 1799, a French soldier in Napoleon's army discovered a gray slabof stone built into a fort near the Egyptian town known as Rashid orRosetta. The stone was inscribed with religious proclamations writtenin three languages: ancient Greek, hieroglyphics, and a more modernEgyptian script called Demotic. Scholars quickly translated the Greekand Demotic writing and realized the same proclamation was repeatedin all three languages. Unfortunately, the top portion of the slab hadbroken away, leaving only 14 lines of hieroglyphs, but these proved to beenough. A painstaking comparison of the languages and some inspireddetective work allowed researchers to decode the hieroglyphics for thefirst time in more than a millennium. The Rosetta stone became the keyto unlocking a priceless treasury of information about ancient Egyptand its people.

The story of the Rosetta stone is a good example of how archaeologistscan piece together human history by carefully studying rare artifactsthat have survived the rigors of time. Occasionally, evidence of thepast is staring us in the face just waiting to be identified, like the stoneslabs in Karnak. More often the past is buried under debris accumulatedover many centuries, as in the legendary city of Troy in Turkey. The pastcan even be found hiding in the most unlikely of places, such as the detailsof human history recorded in our genetic code.

Teasing out this information from a variety of sources and graspingits significance is far from easy. It has taken several centuries to developthe tools and know-how that enable today's scientists to interpretclues from the past and turn them into an account of human history.Breakthroughs in archaeology and other sciences often have to wait fora chance discovery like the Rosetta stone, or the introduction of a newtechnology, or the unique insights of an imaginative mind. Despite thesedifficulties, scientists persevere because of a deep fascination within allof us: a desire to know about our origins.

Scientists pondering the history of the solar system are much likearchaeologists sifting through the sands of Egypt. They bring differentmethods and tools to the job, but both strive to glean as much as possiblefrom precious relics from the past, and combine this with informationdeduced from our current surroundings. The distances and timescalesmay be different but the big questions are the same. Where do we comefrom? How did we get here? What was the world like in the past? Decipheringthe history of the solar system is archaeology on a grand scale.For human society to arise, our species needed to evolve from thosethat went before. Prior to this, life had to appear on a suitably habitableplanet orbiting a long-lived star. Before any of this could happen, oursolar system had to take form from the near nothingness of interstellarspace. The story of this transformation and how scientists have pieced ittogether is the subject of this book.

A SOLAR SYSTEM TO EXPLAIN

We start by taking stock of the solar system we see today. The solar systemis dominated by a star, the Sun, which contains more than 99.8 percentof the system's mass. Compared to any of the planets the Sun ishuge: roughly 1.4 million km (840,000 miles) across, or 109 times thediameter of Earth. The Sun is a rather ordinary star, but "average" is notquite the right word: it is actually brighter and more massive than 90percent of the stars in our galaxy. The Sun is roughly in the middle of its10-billion-year life span, neither young nor old, and it has few noteworthyfeatures. It lacks the variability, unusual composition, or excessivemagnetic field of some of its more exotic stellar counterparts. From thepoint of view of life on Earth, this is a good thing: a stable and predictablestar provides a pleasant environment for life to flourish.

The average density of the Sun is similar to that of water, but it islargely composed of lighter materials—hydrogen and helium—that aretightly compressed by the Sun's gravity. These two chemical elementsmake up 98 percent of the Sun's bulk, while all the others contribute theremaining 2 percent, a composition that turns out to be a fair reflectionof stars in general. Like other stars, the Sun is made of plasma, anelectrically charged gas that reaches temperatures of millions of degreesin the solar interior. Nuclear reactions in the Sun's core provide a continuoussource of energy that keeps the Sun shining, and this sunlightprovides an important source of heat for Earth and the other planets.

The overwhelming mass of the Sun means that its gravity dominatesthe motion of all the other members of the solar system. To a good approximation,the Sun lies at the center of the system while every otherobject revolves around it. Somewhat surprisingly, the Sun accounts foronly about 2 percent of the solar system's angular momentum, or rotationalinertia. The Sun spins rather slowly, with each rotation takingroughly a month, although the Sun's fluid nature means that differentlayers in its interior rotate at somewhat different speeds. Most of the rotationalenergy of the solar system is carried by the planets as they travelaround the Sun. This fact has puzzled scientists for a long time and hasstrongly influenced theories for the origin of the solar system, as we willsee in Chapter 3.

The Sun has eight major planets. These follow elliptical orbits aroundthe Sun, all traveling in the same direction—anticlockwise whenviewed from above the Sun's north pole. The orbits are almost—but notquite—in the same plane, like concentric hoops lying on a table. Withthe exception of Mercury and Mars, the orbits are very nearly circular.Mercury and Mars follow more elongated paths—in mathematicalterms their orbits are eccentric. The eccentricity of Mars's orbit was animportant clue that helped early astronomers understand the motion ofall the planets, as we will describe in Chapter 2.

A useful yardstick for measuring distances in the solar system is theastronomical unit, or AU for short. This is the average distance betweenEarth and the Sun, roughly 150 million km (93 million miles). Therealm of the major planets extends out to 30 AU from the Sun, but itis divided into two distinct domains. The four inner planets all orbitwithin 2 AU of the Sun. These small objects are called the terrestrial(Earth-like) planets since they all have solid surfaces, and their structureand composition resemble those of Earth.

The four outer planets are arranged more spaciously, orbiting between5 and 30 AU from the Sun. These bodies are giants comparedto the terrestrial planets. Jupiter, the largest, is 300 times more massivethan Earth. The giant planets are constructed in a very different waythan their rocky cousins, consisting of multiple layers of gas and liquidwith no solid surface.

Each of the giant planets forms the hub of a system of rings and aconsiderable family of satellites. Saturn's spectacular rings are made upof countless chunks of almost pure water ice, ranging in size from a fewmeters (several feet) down to tiny specks of dust. The rings of Jupiter,Uranus, and Neptune are much darker and less extensive by comparison.As we write, astronomers have found 168 moons orbiting the fourgiant planets, but it seems almost certain that more will be discoveredin the future. In marked contrast, the inner planets have only threesatellites—our own Moon and Mars's two tiny companions, Phobos andDeimos. None of the terrestrial planets has rings.

Before we move on to asteroids, comets, and the other members ofthe solar system, we need to take a moment to describe how astronomersclassify things. Astronomical bodies can be grouped in many differentways: based on their shape (roughly spherical or irregular), theircomposition (rocky or icy), their appearance through a telescope (fuzzylike a comet or a single point of light), or the nature of their orbits.When it comes to planets, however, the popular feeling is that size isthe most important factor: a planet is something that is smaller than astar but larger than everything else. The question is how large. Billionsof objects orbit the Sun, ranging in size from Jupiter, with a diameter 11times larger than Earth, down to microscopic grains of dust. Nature hasno regard for our habit of allocating objects to particular pigeonholes.To a large extent, the dividing line between a major planet and a smallerbody is arbitrary, much like the distinction between a river and a stream.

According to the current convention, our solar system has eightmajor planets. Pluto used to belong to this club, but astronomers recentlymoved it to a different category based on its similarity to otherobjects in the outer solar system. This rearrangement didn't please everybody,and Pluto's status remains a topic of debate. With remarkableforesight, astronomer Charles Kowal reflected on the problem of how todefine a planet in his 1988 book on asteroids. The largest known asteroid,Ceres, is 952 km (592 miles) in diameter, while Pluto—which wastreated as a major planet at the time—is just over 2,300 km (1,400 miles)across. "What will happen if an object is found with a diameter of 1500km?" Kowal asked. "Will it be called an asteroid or a planet? You can besure that astronomers will not answer this question until they are forcedto!" On this last point he was entirely correct.

The day of reckoning came in 2003 when astronomers discoveredfour large objects orbiting beyond Neptune. Three of these, Makemake,Haumea, and Sedna, appear to be about 1,500 km (900 miles) in diameter.The fourth, Eris, is roughly the same size as Pluto but about 27percent more massive. If Pluto is called a planet, then surely Eris shouldbe as well. Should we classify the other three new objects as planets too?What will happen when more large objects are discovered? Will theresoon be 20 planets, or 50, or 1,000? It was time for a reappraisal. Ina controversial decision, the International Astronomical Union (IAU)voted to create a new class called "dwarf planets," with Pluto, Eris, andasteroid Ceres as founder members. Pluto, formerly a major planet, wasredesignated minor planet number 124340, reducing the number ofmajor planets to eight.

As of 2012, only five objects have been added to the list of dwarfplanets. That still leaves many thousands of known objects that are notplanets, dwarf planets, or moons. According to the IAU, these are "smallsolar system bodies," a category that is divided into "comets," icy bodiesthat sometimes develop a fuzzy coma and a tail, and "minor planets,"rocky objects that always look like points of light when seen from Earth.Few people actually use the term "minor planet" in practice, and smallrocky objects are almost always called "asteroids" instead.

A major belt of asteroids lies between the terrestrial and giant planets.Astronomers have found over 300,000 asteroids so far, mostly concentratedbetween 2.1 and 3.3 AU from the Sun. Hundreds more are discoveredevery month. Close-up pictures show that asteroids look verydifferent from planets: they are often elongated or have irregular shapes,and their surfaces are covered in ridges, boulders, and craters. Despitetheir great number, the asteroids contain relatively little mass in total. Ifall the known asteroids were combined into a single object, it would besmaller than Earth's Moon.

The vast majority of asteroids lie in this main belt between Mars andJupiter, but some venture farther afield. Asteroid Eros crosses the orbitof Mars, and in 1931 it came within 23 million km (14 million miles)of Earth—about half the minimum distance to Venus. Another asteroid,Hidalgo, moves on a highly elliptical orbit that takes it out beyondSaturn. Some asteroids even cross Earth's orbit, and a small fraction ofthese will eventually collide with our planet. Two large groups of asteroids,called Trojans, share an orbit with Jupiter, traveling in locksteparound the Sun 60 degrees ahead of the planet or 60 degrees behindit. Astronomers have recently found similar Trojan asteroids that shareorbits with Mars and Neptune.

Another belt of small bodies orbits the Sun just beyond Neptune.This region, called the Kuiper belt, is home to Pluto, Eris, and hundredsof other objects found within the past two decades. These discoveriesare probably just the tip of the iceberg, and the Kuiper belt probablycontains far more mass than the main asteroid belt. Astronomers usuallyrefer to bodies orbiting beyond Neptune as Kuiper belt objects ortrans-Neptunian objects to distinguish them from "asteroids," a termthat has come to mean small bodies in the inner part of the solar system.

Only a handful of comets have been viewed at close range. These typicallylook rather like asteroids, although they contain large amounts ofice as well as rocky dust. Comets remain inert as long as they stay cold.However, if a comet comes within a few AU of the Sun, its ices begin tovaporize, releasing gas that blows dust grains off the surface. This gasand dust accumulates around the solid nucleus, forming a huge diffusecloud called a coma, and streaming away into space to form tenuoustails (one of gas, one of dust) that can extend for millions of kilometers(millions of miles).

Asteroids orbit within a few AU of the Sun, and astronomers had longassumed they were free of ice. In 1996, asteroid Elst-Pizarro surprisedmany people by developing a tail like a comet as it passed the point in itsorbit closest to the Sun (Figure 1.2). In 2001 and 2007, the same thinghappened again. Elst-Pizarro is now classed as both a comet and an asteroid.Several other objects in the outer parts of the asteroid belt displaythis dual personality. These bodies must harbor reservoirs of ice thatpartially vaporize when the temperature becomes high enough. Icy depositshave recently been detected on the surface of Themis, one of thelargest asteroids in the main belt. It may be that other asteroids containice in their interior, protected from sunlight by a layer of rocky dust onthe surface. Clearly, the boundary between asteroids and comets is notas sharp as astronomers once believed.

Most comets follow highly elongated orbits, arriving in the innersolar system from beyond Neptune and then making the return journey.A few hundred comets have become trapped on smaller orbits bythe pull of Jupiter's gravity, and these rarely travel much beyond thegiant planet's orbit. Typically, these "Jupiter family comets" have traveledaround the Sun many times, losing much of their former glory overtime. Most comets move on much larger orbits by comparison, takingthousands or even millions of years to travel around the Sun. Tracingthe motion of these "long-period" comets backward in time along theirorbits shows that they come from a vast reservoir of icy bodies far fromthe Sun. This spherical swarm of comets, known as the Oort cloud, isconcentrated between 20,000 and 50,000 AU from the Sun, and it marksthe true outer boundary of the solar system.

REAL WORLDS

Any successful scenario for the origin and evolution of our solar systemneeds to account for the overall structure of the planetary system.It also needs to explain the nature of individual objects, including featuresthat are readily apparent such as the cratered surface of the Moon,and information buried deep within planetary interiors. For centuries,astronomers had little on which to base their theories. Most objects inthe solar system appeared as tiny circles or points of light through atelescope. Even today, the best telescopes cannot obtain images or dataas detailed as those from a passing spacecraft.

The dawn of the space age marked a dramatic turning point in howwe view the solar system. Space flight allowed astronauts to visit theMoon and bring back 382 kg (842 pounds) of lunar rocks, prompting aburst of new research on Earth's nearest neighbor. Space missions alsotransformed many hazy images and tiny points of light into real worldsthat could be mapped, probed, and studied scientifically, providing vastamounts of new data.

(Continues...)

Excerpted from FROM DUST TO LIFE by JOHN CHAMBERS, JACQUELINE MITTON. Copyright © 2014 John Chambers and Jacqueline Mitton. Excerpted by permission of PRINCETON UNIVERSITY PRESS.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

Edition details

• Publisher: Princeton University Press
• Publication date: 2013
• ISBN 10: 0691145229
• ISBN 13: 9780691145228
• Binding: Hardcover
• Language: English
• Number of pages: 320