When the Earth Had Two Moons: Cannibal Planets, Icy Giants, Dirty Comets, Dreadful Orbits, and the Origins of the Night Sky

by Erik Asphaug

Overview

This expert guide to plant formation and the origins of life “makes the solar system an even weirder and more wonderful place than it seemed before” (Wall Street Journal).

In 1959, the Soviet probe Luna 3 revealed an astonishing truth: the far side of the moon is an enormous mountainous expanse, completely different from the vast lava-plains on the side facing Earth. But why would the two side of the moon be so different? And what might this tell us about our own place in the universe? As it turns out, quite a lot.

Fourteen billion years ago, the universe exploded into being, creating galaxies and stars. Planets formed out of the leftover dust and gas that coalesced into larger and larger bodies orbiting around each star. In a sort of heavenly survival of the fittest, planetary bodies smashed into each other until solar systems emerged. Curiously, instead of being relatively similar in terms of composition, the planets in our solar system, and the comets, asteroids, satellites and rings, are bewitchingly distinct. So, too, the halves of our moon.

In When the Earth Had Two Moons, esteemed planetary geologist Erik Asphaug takes us on an exhilarating tour through the farthest reaches of time and our galaxy. Beautifully written and provocatively argued, When the Earth Had Two Moons is not only a revealing look at outer space, but a profound inquiry into the nature of life here.

Product Details

ISBN-13:	9780062657947
Publisher:	HarperCollins
Publication date:	03/19/2024
Sold by:	Barnes & Noble
Format:	eBook
Pages:	368
Sales rank:	432,169
File size:	55 MB
Note:	This product may take a few minutes to download.

About the Author

Erik Asphaug is a professor in the Lunar and Planetary Laboratory at the University of Arizona. He studies planet formation and evolution and has been on the science teams of numerous past and upcoming NASA and international space missions. He lives with his family in Arizona.

Editorial Reviews

10/01/2019

Asphaug's love of the cosmos and his desire to understand the way it works led him to a career as a professor of planetary science at the University of Arizona. In this work, his passion shows clearly in his writing. The introduction asks readers to imagine Earth with two moons, one large and one small. The author opines that Earth had two moons at one point in the distant past, and notes that the far side of the moon is dramatically different from the near side as first shown by the Soviet space probe Luna 3 in 1959. The far side has a much thicker crust and more impact craters, while the predominant features of the near side are the large dark regions known as maria (seas). This and that the moon is slightly oblong suggest that Earth had two moons that eventually collided to form the moon we have today, an event that tells a great deal about the solar system itself. The author further explores how planets were formed, and why many are so different from one another. VERDICT A fun read from an award-winning scientist. Asphaug's literary skill shines throughout this entertaining work.—Dave Pugl, Ela Area P.L., Lake Zurich, IL

Library Journal

08/26/2019

Asphaug, a University of Arizona professor of planetary science, takes readers on an initially promising, ultimately somewhat disappointing tour of the solar system. Exploring a variety of planetary forms—including comets, asteroids, moons, and the sun—he depicts the system in its entirety as a dynamic, complex, and deeply mysterious place. For instance, there’s Iapetus, one of Saturn’s eight moons, dubbed a “walnut moon” because of a 20-kilometer-high ridge that circles its equator, about which Asphaug concludes, “Ideas for how it formed are rather crazy, but one of them is true, or none of them are crazy enough.” Asphaug integrates his own research with that of others, yielding a firsthand account of cutting-edge science, including his titular hypothesis that early in Earth’s history it had two moons. He posits that the smaller satellite crashed into the moon, leading to the stark differences in composition between its two sides. He also hypothesizes about the origin of life, discussing how microscopic organisms might well have migrated among celestial objects. Asphaug makes for an enthusiastic and erudite guide to these and other subjects, but his overly technical language will likely frustrate general readers attracted by his compelling material. (Oct.)

Publishers Weekly

Delightful. ... The story swings from the birth of the universe, through the history of astronomy, to the modern understanding of the piece-by-piece building of the planets. ... Makes the solar system an even weirder and more wonderful place than it seemed before.” — Wall Street Journal

“A gripping and endlessly fascinating account of how planets formed.” — Alan Stern, planetary scientist and leader of NASA’s New Horizons mission to Pluto

"If the planets were born out of material orbiting the Sun, like raindrops condensing from a cloud, why do they differ so much in structure and chemical composition? This detailed book assesses the astronomical and geological evidence on the origin of planetary diversity." — Nature. "Best Science Picks of the week"

“When the Earth Had Two Moons is a lyrical exploration of our solar system, introducing not just the facts of its formation and nature but the implications for all of us living on Earth.” — Amy Mainzer, visiting scientist at the Jet Propulsion Laboratory and professor of planetary science at the University of Arizona

“An enthusiast as well as a fine writer, Asphaug lays it out from the beginning. . . . An expert, entertaining review of what’s known about the solar system.” — Kirkus Reviews

“Asphaug draws upon his years of research and expertise to provide the reader with a truly wondrous and surprising exploration of planet formation and the origins of life. A meticulous and expertly presented work of science, When the Earth Had Two Moons is unreservedly and enthusiastically recommended.”
— Midwest Book Review

 “An enthusiastic and erudite guide.” — Publishers Weekly

From the Publisher

When the Earth Had Two Moons is a lyrical exploration of our solar system, introducing not just the facts of its formation and nature but the implications for all of us living on Earth.

Amy Mainzer

A gripping and endlessly fascinating account of how planets formed.

Alan Stern

"If the planets were born out of material orbiting the Sun, like raindrops condensing from a cloud, why do they differ so much in structure and chemical composition? This detailed book assesses the astronomical and geological evidence on the origin of planetary diversity."

Nature. "Best Science Picks of the week"

Asphaug draws upon his years of research and expertise to provide the reader with a truly wondrous and surprising exploration of planet formation and the origins of life. A meticulous and expertly presented work of science, When the Earth Had Two Moons is unreservedly and enthusiastically recommended.”

Midwest Book Review

Delightful. ... The story swings from the birth of the universe, through the history of astronomy, to the modern understanding of the piece-by-piece building of the planets. ... Makes the solar system an even weirder and more wonderful place than it seemed before.

Wall Street Journal

Delightful. ... The story swings from the birth of the universe, through the history of astronomy, to the modern understanding of the piece-by-piece building of the planets. ... Makes the solar system an even weirder and more wonderful place than it seemed before.

Wall Street Journal

Narrator Adam Verner’s friendly, leisurely cadence immediately invites listeners into Eric Asphaug’s discussion of the origins of our solar system. The renowned planetary geologist examines planetary formation, revealing new insights on perceptions of creation. From Kepler’s laws to giant impact theory, Asphaug’s concise writing style makes the subject accessible. Some of the information is complex, and Verner takes his time walking listeners through the material. In doing so, he captures Asphaug’s conversational tone as well as his passion for his subject. Verner’s engaging narration makes this audiobook enjoyable no matter what level of scientific background the listener has. D.M.W. © AudioFile 2019, Portland, Maine

DECEMBER 2019 - AudioFile

Narrator Adam Verner’s friendly, leisurely cadence immediately invites listeners into Eric Asphaug’s discussion of the origins of our solar system. The renowned planetary geologist examines planetary formation, revealing new insights on perceptions of creation. From Kepler’s laws to giant impact theory, Asphaug’s concise writing style makes the subject accessible. Some of the information is complex, and Verner takes his time walking listeners through the material. In doing so, he captures Asphaug’s conversational tone as well as his passion for his subject. Verner’s engaging narration makes this audiobook enjoyable no matter what level of scientific background the listener has. D.M.W. © AudioFile 2019, Portland, Maine

DECEMBER 2019 - AudioFile

2019-08-07
The sun and every body in its vicinity formed from the same primordial dust, yet every planet, moon, comet, and asteroid is different. This accomplished overview of planetary science describes the details.

The first photograph from another planet was the rocky surface of Venus, transmitted from a Russian lander in 1975. More Soviet Venus probes followed, and while NASA has been responsible for most of the rest, other nations are getting into the act. The result, featuring contributions from high-tech telescopes and computer simulations, is an explosion of information about our solar system and, more recently, solar systems throughout our galaxy. An enthusiast as well as a fine writer, Asphaug (Planetary Science/Univ. of Arizona) lays it out from the beginning. Despite their flawed theories, when the ancients observed and calculated, they proved that Earth was a sphere and measured its diameter and the distance to the moon and predicted eclipses. Geniuses from Copernicus to Einstein improved the big picture, but it was well into the 20th century before interesting details became clear. That meteor strikes formed the moon's craters remained controversial until the Apollo landings proved it. After a nod to the Big Bang and formation of the sun, Asphaug concentrates on the history and current knowledge of the planets, familiar and unfamiliar moons, and unattached bodies in between. As an earthling, he favors earthlike features, and readers will share his pleasure as he discusses them. Rivers, lakes, oceans, and rain? Saturn's moon, Titan, has them; Mars and perhaps Venus once enjoyed the same. Life began in water, so scientists are thrilled when they find it elsewhere. Ice doesn't qualify, but there is evidence for liquid water oceans under the icy surface of Jupiter's Ganymede and Europa, Saturn's Enceladus, perhaps Mars, and even some asteroids and comets.

An expert, entertaining review of what's known about the solar system.

Kirkus Reviews