A fascinating book on life inside the Earth
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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 …
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.