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Media we love: Planet Earth, Past and Present

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Kelly Kizer Whitt

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January 4, 2024

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Planet Earth, Past and Present

If you’re ready to take a deep dive into Earth’s evolution and habitability and compare it with other worlds, then I have got the book for you. Planet Earth, Past and Present: Parallels Between Our World and its Celestial Neighbors by Michael Carroll is a thorough examination using the latest scientific information and incredible artwork by the author. Each chapter compares Earth to other worlds, from the asteroid belt to Venus, Mars, Titan and even exoplanets.

The book begins by putting us in our place. Carroll describes Earth’s place in the Milky Way galaxy:

Our location in the galaxy is significant, as it appears that – like planetary systems – galaxies have habitable zones.

An astonishing 95% of the Milky Way’s suns may not be able to sustain habitable planets, because many orbit the galaxy in paths that carry them through the deadly spiral arms. Any star that passes through one of these starry swarms is subject to deadly radiation from the congested stars. Our own solar system orbits far enough from the center to keep it in sync with the rotation of the rest of the galaxy, so that it remains in the quieter space between the spiral arms. The Earth and its planetary siblings are well placed in a quiet, resource-rich niche of a vast and complex galaxy.

A special place in our solar system

Earth is not only in a special place in our galaxy, explains Carroll, but also a special place in our solar system. These areas that we call habitable zones might be surprisingly narrow, at least for life as we know it. Carroll describes work by the astrophysicist Michael Hart in the 1970s. He says:

Astrophysicists have been able to demonstrate that had the Earth formed only 5% closer to the sun, our planet would have experienced a runaway greenhouse effect, making us more of a twin to Venus than we already are. Had our planet arisen a scant 1% farther away, Earth would have suffered a runaway glaciation, with the surface and oceans freezing over in a permanent snowball Earth condition. Hart’s models indicate that both of these situations – frozen or baked – are irreversible.

Carroll’s illustrations

Carroll is well-known for his amazing illustrations of astronomical worlds and events, and with good reason. His images help us better picture things we’ll never get to see and capture scenes and moments that we wish we could experience. The book is rich with his illustrations along with images from NASA and other illustrators.

Below is an illustration showing the moments before a cataclysmic event that scientists believe produced our moon. A giant rocky body, named Theia, crashed into the early Earth, stripping off part of our planet and fracturing Theia. The debris eventually coalesced into what we know as our present-day moon.

A mostly dry landscape with many small craters and a distant volcano, while in the sky a giant cratered moonlike object rises above the horizon. — This Michael Carroll illustration shows the pending impact that eventually formed Earth’s moon. The caption reads, in part: “Hours before impact, the Mars-sized planet Theia looms over the horizon of the early Earth.” Image via Michael Carroll/ Springer Publishing.

In this next illustration, Carroll depicts early Earth, before the Great Oxygenation Event, when concentrations of oxygen rose in our atmosphere and oceans.

A shore with some rocky outcroppings, an purplish sky with white clouds and waves rolling onto the beach with an emerald green and teal color. — “A billion years before the Great Oxygenation Event, most land masses consisted of volcanic islands or raised impact crater rims. Ocean water would have been a remarkable green from suspended iron, and photochemicals would have tinted the sky toward an orange hue. The continents began to rise from the waters just over 3 billion years ago.” Image via Michael Carroll/ Springer Publishing.

In the book, we also get a peek at early Earth while it was largely covered with ice and snow and before the moon was covered with all the craters we now recognize.

An image of Earth covered largely in snow and ice with some large blue patches and a moon that does not yet have all the craters we're familiar with. — “The snowball Earth: 700 million years ago, our planet may have been covered from pole to pole by vast ice sheets. Here, coastlines of the supercontinent Rodinia are just visible through the planet’s global ice covering. A band of open water and clear land along the equator begins the process of global melting, perhaps due to increased volcanic activity. The moon’s bright rayed crater Copernicus is very young, and Tycho has not yet appeared.” Image via Michael Carroll/ Springer Publishing.

Bottom line: Learn about Michael Carroll’s book Planet Earth, Past and Present. The richly illustrated book looks at history, habitability, our solar system and more.

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January 4, 2024

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Space

Kelly Kizer Whitt

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About the Author:

Kelly Kizer Whitt - EarthSky’s nature and travel vlogger on YouTube - writes and edits some of the most fascinating stories at EarthSky.org. She's been writing about science, with a focus on astronomy, for decades. She began her career at Astronomy Magazine and made regular contributions to other outlets, including AstronomyToday and the Sierra Club. She has nine published books, including a children's picture book, Solar System Forecast, and a young adult dystopian novel, A Different Sky.