100-C 25-C 50-C 75-C C+M 50-C+M C+Y 50-C+Y M+Y 50-M+Y 100-M 25-M 50-M 75-M 100-Y 25-Y 50-Y 75-Y 100-K 25-K 25-19-19 50-K50-40-40 75-K 75-64-Preface to the Second Edition
“Knowledge is not static. Science is a process, not a
product. Some of what is presented in this volume
will inevitably be out of date by the time you read
it.” From the Preface to the first edition, 1999.Written on the eve of the new millennium, the statement
above was our acknowledgment that one cannot simply
“freeze” our knowledge of the solar system we inhabit, box
it up, and display it like a collection of rare butterflies in a
19th century “cabinet of curiosities.” Rather our goal was
to provide our readers with an introduction to understand-
ing the solar system as an interacting system, shaped by its
place in the universe, its history, and the chemical and phys-
ical processes that operate from the extreme pressures and
temperatures of the Sun’s interior to the frigid realm of the
Oort cloud. We aimed to provide a work that was useful to
students, professionals, and serious amateurs at a variety of
levels, containing both detailed technical material and clear
expositions of general principles and findings. With the help
of our extremely talented colleagues who agreed to author
the chapters, we humbly believe we achieved at least some
of these ambitious goals.
How to decide when to update a work whose subject
matter is in a constant, exuberant state of flux? Difficult.
Waiting for our knowledge of the solar system to be “com-
plete” was deemed impractical, since our thesis is that this
will never happen. Picking an anniversary date (30 years
since this, or 50 years after that) seemed arbitrary. We com-
promised on taking an informal inventory of major events
and advances in knowledge since that last edition whenever
we got together at conferences and meetings. When we re-
alized that virtually every chapter in the first edition needed
major revisions and that new chapters would be called for to
properly reflect new material, we decided to undertake the
task of preparing a second edition with the encouragement
and help from our friends and colleagues at Academic Press.
Consider how much has happened in the relatively short
time since the first edition, published in 1999. An interna-
tional fleet of spacecraft is now in place around Mars and two
rovers are roaming its surface, with more to follow.Galileo
ended its mission of discovery at Jupiter with a spectacular
fiery plunge into the giant planet’s atmosphere. We have
reached out and touched one comet with theDeep Impact
mission and brought back precious fragments from another
withStardust.Cassiniis sending back incredible data from
the Saturn system and theHuygensprobe descended to the
surface of the giant, smog-shrouded moon Titan, reveal-
ing an eerily Earth-like landscape carved by methane rains.
NEARandHayabusaeach orbited and then touched down
on the surface of near-Earth asteroids Eros and Itokawa, re-
spectively. Scientists on the Earth are continually improving
the capabilities of telescopes and instruments, while labo-
ratory studies and advances in theory improve our ability
to synthesize and understand the vast amounts of new data
being returned.
What you have before you is far more than a minor tweak
to add a few new items to a table here or a figure there. It
is a complete revamping of the Encyclopedia to reflect the
solar system as we understand it today. We have attempted
to capture the excitement and breadth of all this new mate-
rial in the layout of the new edition. The authors of existing
chapters were eager to update them to reflect our current
state of knowledge, and many new authors have been added
to bring fresh perspectives to the work. To all of those au-
thors who contributed to the second edition and to the army
of reviewers who carefully checked each chapter, we offer
our sincere thanks and gratitude.
The organization of the chapters remains based on the
logic of combining individual surveys of objects and plan-
ets, reviews of common elements and processes, and dis-
cussions of the latest techniques used to observe the solar
system. Within this context you will find old acquaintances
and many new friends. The sections on our own home planet
have been revised and a new chapter on the Sun-Earth con-
nection added to reflect our growing understanding of the
intimate relationship between our star and conditions here
on Earth. The treatment of Mars has been updated and a
new chapter included incorporating the knowledge gained