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Intraterrestrials: Discovering the Strangest Life on Earth
A biologist’s firsthand account of the hunt for life beneath earth’s surface—and how new discoveries are challenging our most basic assumptions about the nature of life on Earth
Life thrives in the deepest, darkest recesses of Earth’s crust—from methane seeps in the ocean floor to the highest reaches of Arctic permafrost—and it is unlike anything seen on the surface. Intraterrestrials shares what scientists are learning about these strange types of microbial life—and how research expeditions to some of the most extreme locales on the planet are broadening our understanding of what life is and how its earliest forms may have evolved.
Drawing on her experiences and those of her fellow scientists working in challenging and often dangerous conditions, Karen Lloyd takes readers on an adventure from the bottom of the ocean in submersibles through the jungles of Central America to the high-altitude volcanoes of the Andes. Only discovered in recent decades, “intraterrestrials”—subsurface beings that are truly alien—are demonstrating how life can exist in boiling water, pure acid, and bleach. They enable us to peer back to the very dawn of life on Earth, disclosing deep branches on the tree of life that push the limits of what we thought possible. Some can “breathe” rocks or even electrons. Others may live for hundreds of thousands of years or longer. All of them are living in ways that are totally foreign to us surface dwellers.
Blending captivating storytelling with the latest science, Intraterrestrials reveals what microbes in Earth’s deep surface biosphere can tell us about the prospects for finding life on other planets—and the future of life on our own.
Life thrives in the deepest, darkest recesses of Earth’s crust—from methane seeps in the ocean floor to the highest reaches of Arctic permafrost—and it is unlike anything seen on the surface. Intraterrestrials shares what scientists are learning about these strange types of microbial life—and how research expeditions to some of the most extreme locales on the planet are broadening our understanding of what life is and how its earliest forms may have evolved.
Drawing on her experiences and those of her fellow scientists working in challenging and often dangerous conditions, Karen Lloyd takes readers on an adventure from the bottom of the ocean in submersibles through the jungles of Central America to the high-altitude volcanoes of the Andes. Only discovered in recent decades, “intraterrestrials”—subsurface beings that are truly alien—are demonstrating how life can exist in boiling water, pure acid, and bleach. They enable us to peer back to the very dawn of life on Earth, disclosing deep branches on the tree of life that push the limits of what we thought possible. Some can “breathe” rocks or even electrons. Others may live for hundreds of thousands of years or longer. All of them are living in ways that are totally foreign to us surface dwellers.
Blending captivating storytelling with the latest science, Intraterrestrials reveals what microbes in Earth’s deep surface biosphere can tell us about the prospects for finding life on other planets—and the future of life on our own.
248 pages, Hardcover
First published March 13, 2025
34 people are currently reading
498 people want to read
About the author
Karen G. Lloyd
3 books5 followersKaren G. Lloyd is the Wrigley Chair in Environmental Studies and Professor of Earth Sciences at the University of Southern California. Her work has appeared in leading publications such as Nature and Science.
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Displaying 1 - 24 of 24 reviews
July 5, 2025
3.5 stars. Borrowed on a whim at a recent trip to the library. Fascinating topic that I've never thought about. Chemistry and biology were some of my worst science subjects though, so I started getting a bit lost halfway through 🤣
May 26, 2025
Very understandable and personal summary by a practicing scientist in this field of what is currently known regarding the evidence of life deep deep below land surfaces, in volcanoes, deep down in the columns of sea sediments under km of ocean water. I still don’t know what these critters look like, but now know that nobody else does either and how we know they’re down there and a lot about how they live. And how their life times and styles are completely different from ours or any other living thing you’ve ever seen (much) closer to the surface. Truly fascinating!
August 12, 2025
Liked this overall, author's exhuberance about her field is obvious and engaging. A bit overly "sciencey" in parts even though I have a biology degree!
August 28, 2025
I found this book an interesting and entertaining read. It's nicely pitched at the point where both scientists (I am a retired physicist) and non-scientists will find it accessible, though some of the discussion of genetics may be a little opaque to the non-scientist.
The book is part memoir as well as part science book, which I liked as it added some intrest to what could otherwise be a bit dry.
Overall I recommend this to anyone who is interested in science.
The book is part memoir as well as part science book, which I liked as it added some intrest to what could otherwise be a bit dry.
Overall I recommend this to anyone who is interested in science.
November 29, 2025
A fascinating book looking at life that can be found deep underground and in extreme places, from the cold arctic to active volcanoes. Partially based on the author's own research and fieldwork, it shows that life can be found almost anywhere, if you look hard and long enough and questions what could be considered living: a question that would loom large as we search for extraterrestrial life.
The book start by with how to find such lifeforms. While some are 'easy' to find, by digging deeper on the surface, some can only be found in deep mines and by examining core samples from land and marine based sediments. Others can be sampled from areas like volcanoes or permafrost. With the advent of DNA sampling, amplification and sequencing, scientists began to get an idea of just how many microbes can be found from such samples.
While they may look the same as the microbes we are familiar with, many of these intraterrestrial microbes are actually very different. We are all descended from microbes that breath oxygen to get energy. But these intraterrestrial micros have the ability to use methane and other chemicals to get energy, and can live in extreme environments like high temperature or pressure or in highly acidic or alkaline environments. This has opened up other branches of life, of which multicellular life is just one branch.
The author then shows that we can get an understanding of how these microbes live by looking at their 'thermodynamic landscape', or the amount of energy provided by chemical reactions. Using oxygen produces a large burst of energy. Other chemical processes also produce energy (but less than oxygen) but in environments without oxygen, such processes are more than enough to power life. These chemical processes can alter the microbe's environment, which can then affect the kinds of microbes that can live in it, in a feedback loop. This leads to different kinds of microbes inhabiting the different layers of sediment, depending on their depth or distance from the source of food. Sometimes, volcanic lakes may have different microbe populations after eruptions, depending on which microbes gain an advantage.
For microbes living deep in marine sediments or under rocks, the amount of energy available can be quite low. This makes them long-lived and slow growing, which makes it harder (and longer) to run experiments to determine if the microbes are alive. The evidence shows that some of these microbes possibly take thousands of years to divide. With such long life spans, the question of evolution comes into the picture. Here, the author speculates that evolution has driven such microbes to be long-lived and wait from geological events to push them into places where they can begin to grow and multiply. Similarly, some microbes living in the arctic permafrost may be waiting for changes in the climate (warming events) before they become more active.
In closing, the book shows that life can be found almost anywhere in the earth, and it is very different from the life that we used to on the surface.
The book start by with how to find such lifeforms. While some are 'easy' to find, by digging deeper on the surface, some can only be found in deep mines and by examining core samples from land and marine based sediments. Others can be sampled from areas like volcanoes or permafrost. With the advent of DNA sampling, amplification and sequencing, scientists began to get an idea of just how many microbes can be found from such samples.
While they may look the same as the microbes we are familiar with, many of these intraterrestrial microbes are actually very different. We are all descended from microbes that breath oxygen to get energy. But these intraterrestrial micros have the ability to use methane and other chemicals to get energy, and can live in extreme environments like high temperature or pressure or in highly acidic or alkaline environments. This has opened up other branches of life, of which multicellular life is just one branch.
The author then shows that we can get an understanding of how these microbes live by looking at their 'thermodynamic landscape', or the amount of energy provided by chemical reactions. Using oxygen produces a large burst of energy. Other chemical processes also produce energy (but less than oxygen) but in environments without oxygen, such processes are more than enough to power life. These chemical processes can alter the microbe's environment, which can then affect the kinds of microbes that can live in it, in a feedback loop. This leads to different kinds of microbes inhabiting the different layers of sediment, depending on their depth or distance from the source of food. Sometimes, volcanic lakes may have different microbe populations after eruptions, depending on which microbes gain an advantage.
For microbes living deep in marine sediments or under rocks, the amount of energy available can be quite low. This makes them long-lived and slow growing, which makes it harder (and longer) to run experiments to determine if the microbes are alive. The evidence shows that some of these microbes possibly take thousands of years to divide. With such long life spans, the question of evolution comes into the picture. Here, the author speculates that evolution has driven such microbes to be long-lived and wait from geological events to push them into places where they can begin to grow and multiply. Similarly, some microbes living in the arctic permafrost may be waiting for changes in the climate (warming events) before they become more active.
In closing, the book shows that life can be found almost anywhere in the earth, and it is very different from the life that we used to on the surface.
August 19, 2025
Apparently the biogeochemist (who even knew there was such a thing) Karsten Pedersen 'coined the term "intraterrestrials" to describe the abundant life within Earth's crust.' The idea of this book is boldly go and explore new life that is found below the surface and of which we have historically known very little.
I must admit I winced a bit when the introduction yet again featured a diary entry from an author about to set off an expedition of discovery, in this case about to start a deep sea dive. This has become a cliché, which I hope we'll move on from soon. But that doesn't stop the actual content being fascinating. Inevitably we get plenty on extremophiles (living in everything from water well over boiling point to strong acids and alkalis) and the origins of life, something anyone reading this kind of popular science is likely to have come across, but there is plenty more, particularly around life dependent on volcanoes, that was new to me.
Karen Lloyd gives us the basics of DNA that will be necessary to understand the findings, plus an introduction to the view of life from thermodynamics, as a system that is kept away from equilibrium. She finishes by asking 'What can intraterrestrials do for us?' This ranges from keeping oxygen free for use to detoxifying waste. We get a picture of the impact these bacteria may have on climate change and their potential relevance to both carbon capture and storage and deep sea mining.
I don't think I'm a natural audience for this book as for me it veers a little too much into the memoir side of popular science. I'm less interested in experiences and more in the science - but I know for many this kind of approach makes the science more engaging, and as such it's recommended.
I must admit I winced a bit when the introduction yet again featured a diary entry from an author about to set off an expedition of discovery, in this case about to start a deep sea dive. This has become a cliché, which I hope we'll move on from soon. But that doesn't stop the actual content being fascinating. Inevitably we get plenty on extremophiles (living in everything from water well over boiling point to strong acids and alkalis) and the origins of life, something anyone reading this kind of popular science is likely to have come across, but there is plenty more, particularly around life dependent on volcanoes, that was new to me.
Karen Lloyd gives us the basics of DNA that will be necessary to understand the findings, plus an introduction to the view of life from thermodynamics, as a system that is kept away from equilibrium. She finishes by asking 'What can intraterrestrials do for us?' This ranges from keeping oxygen free for use to detoxifying waste. We get a picture of the impact these bacteria may have on climate change and their potential relevance to both carbon capture and storage and deep sea mining.
I don't think I'm a natural audience for this book as for me it veers a little too much into the memoir side of popular science. I'm less interested in experiences and more in the science - but I know for many this kind of approach makes the science more engaging, and as such it's recommended.
August 12, 2025
Connection is so key to advancing science and this book (and the author’s career) abounds in this regard. This is up there with Lovelock in terms of refocusing the idea of geobiology. I think it is an excellent read for anyone who is wondering at the edge of biology, geology, and chemistry and interested not only in the foundational character of life on earth, but also in the philosophical gains which come from science.
Unlike many sci com books, I don’t feel this one wastes the reader’s time no matter your level of experience in the fields discussed. It really is for everyone and it’s scientific. Lloyd weaves a fascinating tale of field and lab work, simple organisms and complex systems and the struggles of modern research. I simultaneously felt as a bio and geo major that she did such a thorough job of reminding me of so many fundamental concepts while also relating them to other things. It’s mind bending to think about individual organisms with life strategies oriented around subduction. Not many sci com books these days can lay claim to the coinage of new terms like aeonophiles. Still fewer can bring an expansive, young, and often defeatingly intradisciplinary field to life. I was inspired and so will you be!
Unlike many sci com books, I don’t feel this one wastes the reader’s time no matter your level of experience in the fields discussed. It really is for everyone and it’s scientific. Lloyd weaves a fascinating tale of field and lab work, simple organisms and complex systems and the struggles of modern research. I simultaneously felt as a bio and geo major that she did such a thorough job of reminding me of so many fundamental concepts while also relating them to other things. It’s mind bending to think about individual organisms with life strategies oriented around subduction. Not many sci com books these days can lay claim to the coinage of new terms like aeonophiles. Still fewer can bring an expansive, young, and often defeatingly intradisciplinary field to life. I was inspired and so will you be!
December 17, 2024
Before we start to search for life elsewhere in the Universe, there is much still to learn about the life beneath our feet. Scientist Karen G. Lloyd tells us about organisms that live in boiling hot springs, inside volcanoes, in the driest deserts, on the highest mountains, in permafrost, and in mud in the deepest depths of the sea, and how they have metabolisms that allow them to survive -- just about. To breathe, they don't necessarily use oxygen, but iron, sulphur, even uranium. Though sometimes they grow so slowly that it might take them millions of years to reproduce. And this, of course, allows us to set some parameters about the necessities for life, not just on Earth, but anywhere in the Universe. So we come full circle. In a text that combines a rigorous work-out of the principles of thermodynamics (TRIGGER WARNING: there are equations) with breathtaking all-action adventure, our intrepid heroine ventures from the high Arctic to deep-sea hydrothermal vents in search of the limits of life. This is one of the most exciting pop-science books I've read in ages [DISCLAIMER: The proofs were sent to me so that I could consider writing a blurb].
October 10, 2025
Intraterrestrials: Discovering the Strangest Life on Earth by Karen G. Lloyd is an enthralling exploration of life hidden beneath our feet life that challenges everything we thought we knew about biology, evolution, and survival. Lloyd takes readers on an extraordinary scientific adventure, from submersibles probing the ocean floor to treacherous Andean volcanoes and icy Arctic permafrost, revealing a world teeming with microbial life that thrives where life shouldn’t exist.
What makes Intraterrestrials remarkable is its blend of rigorous science and vivid storytelling. Lloyd writes with the curiosity of a field biologist and the voice of a natural storyteller, drawing readers into a realm where organisms breathe rocks, consume electrons, and live for millennia. These discoveries not only redefine the boundaries of life on Earth but also deepen our understanding of where life might exist beyond it.
More than a work of science, Intraterrestrials is a testament to human wonder the drive to uncover what lies beyond the known and to ask the most profound questions about our place in the universe.
What makes Intraterrestrials remarkable is its blend of rigorous science and vivid storytelling. Lloyd writes with the curiosity of a field biologist and the voice of a natural storyteller, drawing readers into a realm where organisms breathe rocks, consume electrons, and live for millennia. These discoveries not only redefine the boundaries of life on Earth but also deepen our understanding of where life might exist beyond it.
More than a work of science, Intraterrestrials is a testament to human wonder the drive to uncover what lies beyond the known and to ask the most profound questions about our place in the universe.
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May 13, 2025"Is there such a thing as a ‘beach read on microbial thermodynamics’? That was how Karen Lloyd, the author of Intraterrestrials, informally billed her book when talking to her friends in science — and at a beach-bag-friendly 200 pages or so, this lively and compulsively engaging book is an unusual page-turner. Lloyd, a geomicrobiologist, expertly guides readers who have a taste for biological adventures to ‘intraterrestrial’ life: microorganisms that survive under the most extreme environmental conditions, such as in Earth’s deep sediments, deep ocean crust, volcanoes and permafrost soil."
https://www.nature.com/articles/d4158...
https://www.nature.com/articles/d4158...
November 9, 2025
I have never read a book that combines riproaring adventure in the field, tremendous intellectual opportunity, terrifying warning of a danger few have heard about, and the real, no-bullshit possibility of redemption for our species. All in an unpretentious voice that downplays the rock-solid science (and never, ever, pretends to know more than is currently knowable). I would give this to any young person interested in science.
September 15, 2025
Focused and to the point, Intraterrestrials is a thought-provoking book on Earth's subsurface biosphere and how its existence challenges our understanding of biology. Your ticket to the underworld awaits. Read the full review on https://inquisitivebiologist.com/2025...
September 27, 2025
Well written, interspersing fascinating science with rollicking adventures, all with a uplifting tone. Opened my eyes to some novel ways of considering life processes, with important implications for addressing the questions of how, where, and perhaps why life began. Connecting geologic and biological processes, rooted in thermodynamics, that can be expressed as a continuum. Reads fast.
October 27, 2025
Really well-written, accessible to the non-scientist. Fascinating description of the intraterrestrials, the microbes that live in vastly different time-scales and in different environments than earthlings on the typically habitable surface of the Earth. Loved the depictions of the fieldwork environment and appreciated how concepts were explained.
December 4, 2025
A very readable book about scientific research and life long commitment.
A wonderful read and well written. Science is served well at an important time in our nation where many question its importance, and don't appreciate the amount of effort and acquired knowledge demanded to achieve success. 5 stars.
A wonderful read and well written. Science is served well at an important time in our nation where many question its importance, and don't appreciate the amount of effort and acquired knowledge demanded to achieve success. 5 stars.
December 24, 2025
4.5 rounded down to 4.
A brilliant book about what lives below the surface of our Earth (from millimeters to kilometers!) and what these organisms can teach us about the origins, and the extremes of life, about biological processes and chemical constraints and much more. The text is well written and engaging. Loved it!
PS: The author's personal research anecdotes make the book even more fun!
A brilliant book about what lives below the surface of our Earth (from millimeters to kilometers!) and what these organisms can teach us about the origins, and the extremes of life, about biological processes and chemical constraints and much more. The text is well written and engaging. Loved it!
PS: The author's personal research anecdotes make the book even more fun!
June 4, 2025
Interesting and many new perspectives
June 15, 2025
Not really a page turner or a quick read, but this book will certainly inform you and increase your knowledge and outlook on life on and in the earth.
July 13, 2025
Lots of interesting information about our
fascinating world. Lots more to discover
about Intraterrestrials on Earth.
fascinating world. Lots more to discover
about Intraterrestrials on Earth.
July 20, 2025
Fascinating: there are single cells that are thousands of years old deep under the earth.
August 17, 2025
Fascinating look at life found in extreme conditions on earth: deep in the oceans, in the earth's crust, and other places where it can't rely on oxygen or energy from the sun.
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September 17, 2025very interesting book!
November 27, 2025
Good written if you have a background of Biology / chemistry the first part of the book will most likly bore you a bit.
Displaying 1 - 24 of 24 reviews