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FROM THE EDITOR
Editor David J. Eicher
Assistant Design Director Kelly Katlaps
EDITORIAL
Senior Editor Mark Zastrow
Production Editor Elisa R. Neckar
Senior Associate Editor Alison Klesman
Associate Editor Jake Parks
Associate Editor Caitlyn Buongiorno
Editorial Assistant Hailey McLaughlin
ART
Illustrator Roen Kelly
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Richard Talcott
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James TrefilKalmbach Media
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PARS International at http://www.parsintl.comCopyright © 2021 Kalmbach Media Co., all rights reserved. This publication
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bank. BN 12271 3209 RT. Not responsible for unsolicited materials.Often we look deep into
space for the latest find-
ings beyond our home
turf. But this is also a golden age of
discovery and understanding of the
solar system. In this issue, we pause
to consider the magnificent vault of
knowledge scientists have gained in
recent times. Associate Editor Jake
Parks summarizes this storehouse
of research in his “Cosmic tour of
the planets” (page 16).
Of course, life would never have
existed on Earth without the Sun, our local nuclear reactor, located
a mere 93 million miles away. The Sun formed in an open cluster
about 4.6 billion years ago. What we know of the formation of our
solar system — gravity pulling the material into a disk that rotates,
helped along by angular momentum — tells us something about the
worlds we are now discovering around other stars nearby in
the galaxy.
The solar system’s eight planets (or nine, for you Pluto fans!)
encompass several basic types — gas giants, ice giants, rocky ter-
restrial worlds, and outer icy Kuiper belt objects. But we also know
that the solar system didn’t always look like it does now to us. Planets
large and small likely migrated into their current positions.
Numerous collisions accreted smaller bodies into bigger ones and
caused important smashups, creating such bodies as our Moon and
the moons of Pluto.
And although Earth lies in the temperate sweet spot for liquid
water, and by extension for life, we also now know that microbes are
far hardier and exist in more challenging extremes than anyone
would have guessed a generation ago. Could the atmospheres of outer
planets hold microbes? The subsurface aquifers on Mars? The icy,
briny, subsurface oceans on outer solar system moons?
The possibilities are astonishing. Let Jake guide you on a whirl-
wind exploration.Close look at
the planets
Yo u r s t r u l y,
David J. Eicher
Editor
Follow the
Dave’s Universe blog:
http://www.Astronomy.
com/davesuniverse
Follow Dave Eicher
on Twitter:
@deicherstarEarth, our home
planet, is a good
base. But other
planetary adventures
await. NASA/JOSHUA STEVENS