Creating First Life: Abiogenesis

  Essay 3: Pools, Rock Pockets, Deep-sea Vents

Note to Our Readers: This is Third of our three Essays on the Evolution of First Life.  Some readers may have elected to skip much of Essay #2, which can be technical in several areas.  But this Essay, Essay #3, takes up lively stories of dramatic Creation in dangerous locations.   

So far, we’ve discussed evolutionary paths that were likely to have been followed in creating the precursors of life, i.e., the Six Key Molecules.

But gathering those precursors together does not necessarily mean that it will all function together to do enclosure, respiration, metabolism, and replication. Protocells (“pre-cells”) might only do three of the four, or protocells might perform all four but in primitive ways. In other words, the earliest protocells might have been more like chemical systems than living systems. 1

How did we get just the right sequences of physics, geology, and chemistry to produce a functional First Organism — the process known as Abiogenesis? What sort of general (and local) environment was required? What materials needed to be at hand? What sort of energy supply? What temperature and what pressure?

There is not much evidence about how Life got from amino acids free-floating in water to the first single-celled, membrane-enclosed proto-bacteria, (or proto-archaea) but there are several models (hypotheses) describing where and how First Life was “put together.” Each model has significant support in the scientific community.

One thing all the models will show us is that early life was adaptable. Life is a strong seeker, a powerful explorer. Life finds a way! Not always, but often, and if not often, often enough! This amazing adaptability has resulted in an incredible diversity of single-celled life forms, and portends even greater abundance of diversity in the realms of multicellular plant and animal life, as we shall see in our next Essay.  

“Extremophiles” — Microbes That Live in the Harshest Environments

Before we look at the eight models, consider where present-day archaea and bacteria are living.  Since they are the simplest organisms we have today, maybe First Life started out in one (maybe more than one) of those environments.

What we find is that modern microbes live in virtually all Earth’s environments today. And since “all” our environments includes some extremely harsh ones, we need to look at those; especially since life most likely started in the early Archaean Eon, when Earth’s intense volcanic activity produced tremendous heat and subterranean pressure.

In fact, most chemotrophs (including the ones we discussed earlier that consume inorganic elements like sulfur and iron) are extremophiles — bacteria and archaea that live in hostile environments, including those of deep Earth.

Since early Earth was much more inhospitable than it is today, this suggests that the first archaea, and/or the first protocells, were also extremophiles. Examples of these Archean Eon extremophile types are as follows:

  • Thermophiles – heat-loving.
  • Psychrophiles – cold-loving.
  • Alkaliphiles – love alkaline conditions.
  • Acidophiles — love acidic conditions
  • Piezophiles, — love high pressure (in the deep oceans or earth).
  • Halophiles – love high salt concentrations.
  • Thermoacidophiles – love both heat and acid. (These are archaea that live around acidic hot springs and in dumps of acidic mining waste.)

It is now known that extremophiles (microorganisms with extraordinary capability to live in the harshest environments on Earth) can specialize to thrive in the deep-sea, ice, boiling water, acid, the water core of nuclear reactors, salt crystals, toxic waste and in a range of other extreme habitats that were previously thought to be inhospitable for life.2

Living bacteria found in ice core samples retrieved from 3,700 meters (12,100 ft) deep at Lake Vostok in Antarctica, have provided data for extrapolations to the likelihood of microorganisms surviving frozen in extraterrestrial habitats or during interplanetary transport. Also, bacteria have been discovered living within warm rock deep in the Earth’s crust. In the laboratory, Metallosphaera sedula bacteria have been grown on meteorites. 3

This variety of acceptable habitats is a good segue to our next section, which talks about the various places on Earth where The Origin of Life may have taken place.

The 8 Models of WHERE (& When & How) “First-Life” Came Together, i.e., Abiogenesis

There are Eight models of where, and when, and How First-Life got its start.

  1. 1. The Little Warm Pool Model
  2. The Hollow Lipid Spheres or “Protocell” Model (maybe a corollary to warm pool model)
  3. The Iron-Sulfide Cavities or “Tiny Pockets in Rocks” Model
  4. The Clay Hydrogel Model
  5. The Silicate-clay Crystal-surface Templates Model (Cairns-Smith Clay Model).
  6. The Deep-hot Biosphere Model
  7. The Deep-Sea Model (maybe a corollary to Deep-Hot model)
  8. The Panspermia Model

We are going to look at each of these eight models in turn. The numbers on this list are simply for reference. There is no real chronology or order of importance here. At present, science has no consensus about which of these eight models are the more probable.

There could well have been some combination of two or more of the models. For example, The Warm Little Pool Model (#1) and The Hollow Lipid Spheres Model (#2) may have been two stages of a single model. It is also possible that different models were followed in different geographic locations on Earth.

The Deep-Hot Biosphere Model (#6) could have taken place before one or more of the others, and The Deep-Sea Model (#7) may be an extension or a variant of The Deep-Hot Biosphere Model (#6).  Panspermia, Model #8, could have preceded all the others. Each of the models supposedly results in one single protocell.  In short, perhaps the eight models ought to be called partial models.

Notice that the important “RNA-World Model” is not on this list. That’s because RNA-World is not really about a particular environment on Earth where life most likely started, nor is it about where and how First Life got its molecular food.  RNA World could have happened in any one of the above location-and-food-source models; although it is most often associated with The Silicate-Clay Crystals Model, because, as we shall see, that model provides “templating.”

Whatever the order, the variety of these eight models, all of which have evidence backing them up, testifies to Life’s power to “find a way.”

As Dr. Ian Malcolm, a character in the film Jurassic Park, says: “If there’s one thing the history of evolution has taught us, it’s that life will not be contained. Life breaks free, it expands to new territories, and crashes through barriers painfully, maybe even dangerously, but, uh, well, there it is… Life will find a way.” 4

  1. The “Little Warm Pond” Model of First Life

Darwin suggested that simple chemicals in small or shallow bodies of water might spontaneously form organic compounds in the presence of energy from heat, light, or electricity from lightning strikes. These organic compounds could then have replicated and evolved to create more complex forms. 5

Darwin’s “little warm pond” or “little warm pool” remains one of the most suggestive explanations for the origin of life. A classic experiment performed by Harold Urey and Stanley Miller in the 1950s brought the problem of the origin of life, and the “little warm pool,” into the laboratory. 6

The Miller-Urey experiment tried, in part, to simulate Darwin’s small pond of water. But was the original Pond(s) a freshwater pond or a tidal saltwater pool?  Was there a body of water that was calm and peaceful anywhere on Earth during the Hadean Eon?  Wouldn’t a strike of lightning or volcanic action (both simulated by Miller-Urey) disrupt the calmness of the water? Wouldn’t a pool or a pond be too spacious and therefore unable to bring the 4 monomers of life close enough together to form chains and become polymers?

Although Miller had made some of the most essential compounds of life, his experiment did not explain how they and other building blocks – such as nucleotides, which make up DNA – first came together in an ordered way, to form the complex molecules necessary for life. 7

  1. The “Hollow Lipid Spheres” Model of First Life

The Hollow Lipid Spheres model is really a corollary to the Warm Little Pond model. If a little warm pond was too big to bring the earliest organic molecules sufficiently close to each other, or provided insufficient protection from outside chemicals and currents, some scientists contend that Hollow Lipid Spheres would have been able to do those two things, because such spheres are often microscopic.

  1. The “Iron-sulfide Cavities,” or “Tiny Pockets in Rocks” Model of First Life

Earlier, we explained how organic spheres composed of self-assembling lipid (fat) molecules could have been the first membranes that enclosed the chemical reactions of the single-celled First Organism.

However, some scientists feel that such a lipid membrane would not have been strong for long enough to allow the earliest simple molecules (monomers) that were the building blocks of life to come together and start functioning as a “team.”

The Iron-sulfide Cavities model contends that First Life did not have to form cell membranes (let alone sturdier outer cell walls), because tiny pockets and fissures in iron-sulfide minerals served to confine and protect each cell’s interior cytoplasm.

We know that hot springs on the ocean floor naturally deposit honeycombs made of the mineral iron-sulfide which are shot through with tiny air pockets a few hundredths of a millimeter across. Drs. William Martin and Michael Russell argue that these pockets are the ideal places for life to get started. 8

The iron-sulfide cavities model is clearly complementary with the Deep-hot and/or Deep Ocean models (#6 and #7) discussed below. Taken together, the iron-sulfide plus the surrounding heat may also have speeded up the chemical reactions that join inorganic molecules together into organic ones.

These combined models also argue that life could have started in this way at many locations and could have persisted under many conditions. 9

Of course, one could conceptually combine the lipid model and the mineral pocket model, arguing that First Life got started in iron-sulfide pockets, and then laid their own cells walls up against the inside walls of the iron-sulfide pockets.

Note:  Many Living cells have cell walls in addition to cell membranes. Cell walls are usually, tougher, thicker substances that form just outside the cell membrane. The walls provide additional protection from the outside environment and can also lend structural strength to the cell.  Bone tissue incudes cells whose walls are partly made of calcium. The cell walls of tree trunks and branches are made tough by cellulose, an organic polymer molecule composed of linked sugar units. [wiki on cellulose 3 and 4] Whether cell walls evolved after or along with cell membranes is outside the scope of this Essay.

  1. The Clay “Hydrogel” Model of First Life

Clays are thought to do two things, and we will talk about each of them as separate models for the emergence of First Life:

  1. They may isolate and protect proto-organic molecular reactions (e.g., allow chaining), and
  2. They may provide scaffolds and templates for fledgling organic molecules to cling to.

The first of these two models is called the Clay Hydrogel Model, and the second is called the Silicate-clay Crystal-surface Templates Model. This section of the Essay is about the first of these two models.

Professor Dan Luo of the Kavli Institute for Nanoscale Science at Cornell, “proposes that in early geological history, clay hydrogel provided a confinement function for biomolecules and biochemical reactions.” 10

Luo and his team knew that in simulated ancient seawater, clay forms a hydrogel — a mass of microscopic spaces capable of soaking up liquids like the tiny pockets in a sponge. Over billions of years, chemicals confined in those spaces could have carried out the complex reactions that formed proteins, DNA and eventually all the machinery that makes a living cell work. Clay hydrogels could have confined and protected those chemical processes until the membrane that surrounds living cells developed.

“To test the idea, Dr. Luo and his team demonstrated protein synthesis in a clay hydrogel in the laboratory. This experiment showed that synthetic hydrogels could be a non-living, “cell-free” medium for protein production.  11

“The researchers believe that when the spongy material is filled with amino-acids plus DNA, the right enzymes, and a few bits of cellular machinery, they could be able to make the proteins for which the DNA encodes, just as might be done in a vat of living cells. 12

“As supporting evidence, geological history shows that clay first appeared — as silicates leached from rocks — just at the time biomolecules began to form into protocells — cell-like structures, but incomplete — and eventually membrane-enclosed cells. The geological events matched nicely with biological events.” 13

As we know, other “scientists previously suggested that tiny balloons of fat or polymers (lipid spheres) might have served as precursors of cell membranes. But clay may be a more promising possibility because biomolecules tend to attach to its surface, and theorists have shown that cytoplasm — the interior environment of a cell — behaves much like a hydrogel. And, Luo said, a clay hydrogel better protects its contents from damaging enzymes (called “nucleases”) that might dismantle DNA and other biomolecules.

  1. The “Silicate Crystals” or “Clay Surfaces” Model of First Life

We’ve already discussed how the hard, geometric surfaces of non-living mineral crystals can form and maintain ordered shapes and can make themselves grow.  Order and growth are characteristics of living things, even though crystals are clearly not living!  This suggests that  crystals may have been inorganic precursors of life. There is evidence that this is so.

We have also seen that the “Little Warm Pool Model” suggested that the earliest amino-acids and nucleotides formed in water solutions. But a minority school of scientists say that these monomers, free-floating in water, would have had little chance of combining into the long polymer strands of proteins, RNA, and DNA respectively. 

The “Silicate Crystals” or “Clay Surfaces” model suggests that complex organic molecules arose gradually by using silicate crystal surfaces as a template or scaffold. This theory holds that the early simple organic molecules would cling to adjacent layers of a silicate crystal substrate. There, they could join up with others to make longer polymer molecules. In other words, the organic cells may have used the inorganic crystals as a scaffolding or substrate on which to build their “working molecules” – the peptides, proteins, and nucleotides. Or, perhaps the crystal surfaces were the templates for linking up chains of peptides, and building the first cell membranes or walls. (See https://sites.google.com/site/originsoflifecarlmont/clay-theory.)

Conceivably, such silicate-clays could have acted as tiny “chemical factories” for processing organic materials into the more complex molecules from which the first life arose. (See  https://sites.google.com/site/originsoflifecarlmont/clay-theory.)

Going further, it is suggestive that silicate-clay crystals can replicate by splitting apart, with one “mother” crystal giving rise to one or more “daughter” crystals. Each crystal can even have its own peculiarities, which it can pass on to its daughter crystals – much like the way living things inherit traits from their parents. And sometimes, when a crystal breaks apart, new quirks can be introduced, for instance because of the stress of breaking. This is similar to the processes of reproduction and genetic mutation, which creates new traits in living things.  14

If the “Clay Surfaces” Model holds true, clay mineral crystals were a link between the worlds of inorganic evolution and biological evolution. 15

What Are “Silicate-Clay Crystals”?

Clay, like any silicate, is made up of crystals. Crystals can grow and accumulate out of solutions. Silicate minerals are the most common of Earth’s minerals, and include quartz, feldspar, and mica. When common clay is examined under a microscope, it is seen to be composed of tiny silicate mineral crystals. Within each crystal, atoms are arranged in a structure that repeats in a tightly-packed, regular pattern.

An individual silicate crystal in a clay suspension naturally forms and extends itself by attaching “loose” atoms from the watery clay around it, similar to the way that a snowflake forms and grows in a cloud consisting of cold water-vapor. Generally, once a crystal formation starts to take on a shape, it continues to grow along that same pattern. 16 When these crystals are held in a watery suspension, they take on the plasticity characteristic of clay.

The Earliest Silicate-Clay Model

In 1949, the Irish scientist J.D. Bernal suggested that clay minerals may have created a meeting place for life’s first molecules. 17 In the mid-1960’s, organic chemist Alexander Cairns-Smith published a controversial book, Seven Clues to the Origin of Life, laying out his hypothesis that self-replication of clay crystals in solution might have provided a simple intermediate step between biologically inert matter and organic life.

The Cairns-Smith theory also contended that when silicate-clays dry out, flakes of them can be blown about by the wind. If they land somewhere where they again become wet, the pre-organic molecules within them could have resumed their processes in a new location. In this way, pre-life could have spread around large areas of land. [sites.google.com Clay Theory. (See the website https://sites.google.com/site/originsoflifecarlmont/clay-theory.)

Through the next four decades, however, diverse laboratory investigations of silicate clays mediating peptide bond formation had only limited success. The peptide molecules that formed in the laboratory were “over-protected” in the laboratory environment, and thus showed no evidence of inheritance or metabolism.

Contemporary Research on the Silicate-Clays Model – Creating Peptides and Nucleotides

A 2009 study at the Rensselaer Polytechnique Institute in Troy NY did show that current-day RNA could have formed on the surface of clays, which act like a catalyst to bring RNA together. 18

In December 2017, a revised theoretical model developed by Erastova and collaborators[37] suggested that peptides could form at the interlayers of layered clays such as so-called “green rust” in early Earth conditions. According to this model, drying of the layered material should provide the energy and co-alignment required for peptide bond formation. Then, a re-wetting should allow mobilization of the newly formed peptides, and a repopulation of the interlayer with new amino-acids. This mechanism would lead to the formation of peptides that are over 12 amino-acids-long after 15 to 20 consecutive washes. 19

Going Further – Crystal Layers May Have Templated the Genetic Code in DNA

Cairns-Smith’s theory went a lot further than the formation of peptides and nucleotides lying along a silicate crystal surface. He also proposed that a DNA molecule might have arisen as a cross-section down through a set of crystal layers: “In that respect,” the layers are “like a DNA molecule, which has base pairs platelets stacked on top of each other. It is the sequence of this stacking which creates the information.” 20

Rebecca Schulman, a bio-engineer at Johns Hopkins University in Baltimore, Maryland, was able to design a laboratory system in which information is coded in a crystal structure. Rather than using naturally-occurring minerals, Schulman used crystals made of nanometer-scale tiles that were made of DNA.  Schulman found, first through computer simulation and then by experiment, that the DNA tiles could stack up in a particular pattern, effectively encoding information in a crystal structure. She had found a way to represent and copy information, in crystal form. 21

[Picture Citations:  http://universe-review.ca/I11-02-clay.jpg ]

 

The “Diamond Variation”

Andrei Sommer of the University of Ulm in Germany proposes that a specific type of crystal – the “hydrogenated diamond” – may have been the crystal that was most able to host the Origin of Life on its surface. It is totally non-toxic and completely biocompatible,” he says. “Hydrogenated diamonds” have gained a rigid outer coating of hydrogen atoms from local gas-emitting volcanoes during Earth’s volcanic age.  When a hydrogenated diamond is wetted, the water molecules line up on the surface as if they were frozen into a crystal layer (an analogy might be static electricity making all the hairs on your head stand up. 22

Surprisingly, these crystal water layers do not disappear when the hydrogenated diamond is fully immersed in water. Because this is the only natural material known to exhibit this behavior, Sommer’s team proposes that small organic molecules in the primordial soup landed on hydrogenated diamonds and were helped by its robust crystal water layers into linking together to form proteins and DNA. 23

Support for this idea comes from a recent study that found that certain nucleobases (the building blocks of DNA and RNA) form an organized pattern on the surface of graphite, which is chemically similar to diamond. 24

Summary Comments on the Silicate-Clays Models

The “Silicate Crystals” or “Clay Surfaces” model holds a minority position today. Most scientists who work on the problem of life’s origin focus instead on how simple sugars, amino-acids, and other organic chemicals came together to form nucleic acids and proteins. 25

On the other hand, Professor Robert Hazen, says this: “Many of life’s most vital molecular building blocks stick to virtually any natural mineral surface…. [including amino-acids, sugars, and the components of DNA and RNA]….What’s more, when several molecules compete for the same piece of crystal real estate, they often cooperate and yield complex surface structures of their own.” 26

If crystals do provide the order life needs to arise, that has implications for the possibility for life beyond Earth. Mineral crystals should be common on rocky worlds, even if those planets have chemical environments quite different from our own. 27

  1. “Deep-Hot Biosphere” Model of First Life

In 1992 the astrophysicist Thomas Gold proposed the theory that life first developed not on the surface of the Earth, but several kilometers below Earth’s surface, and widely distributed across the Earth 28

The discovery in the late 1990s of nanobes (filament structures that are smaller than bacteria, but that may contain DNA, found in deep rocks) [33] may support Gold’s theory. Gold’s theory posited that the main flow of food to these extremophiles came from primordial methane gas rising out of Earth’s interior mantle.

In a paper called, “The Deep Hot Biosphere,” Gold wrote that “This model holds that the first living things were single-cell microorganisms that were the ancestors of both bacteria and archaea. Gene sequencing studies can be used to reconstruct the bacterial phylogeny (ancestry trees), and these studies indicate that the most recent common ancestor of bacteria and archaea was probably a hyperthermophile (extreme heat-lover) that lived about 2.5 billion–3.2 billion years ago, probably near an underwater volcanic vent or hot springs.

If Gold’s model is correct, the earliest life on land may have been organisms some 3.22 billion years ago. 29

It is also reasonably well established that microbial life is plentiful, today, at depths in the Earth up to five kilometers below the surface. Most of them are extremophile (“loving harsh conditions”) archaea, rather than bacteria, which typically live in more temperate zones near and at the surface. Studies reveal a rich subterranean ecosystem that is almost twice the size of all the world’s oceans. Scientists estimate this subterranean biosphere is teeming with micro-organisms totaling hundreds of times the combined weight of every human on the planet. 30

Methanogens (anaerobic microbes which generate methane as a by-product) have been found in several extreme environments on Earth, including hot dry deserts and buried under kilometers of ice. Microbes making methane were found in a glacial ice core sample retrieved from about three kilometers under Greenland by researchers from the University of California, Berkeley. They also found a constant metabolism able to repair macromolecular damage at temperatures ranging from 293 to –40 °Fahrenheit.  31

There is also molecular, microscopic, and metagenomic evidence that [“iron-eating”] cyanobacteria predominate in deep subsurface rock samples from southwestern Spain. Results suggest that they may play an important role as primary [food] producers within the deep-Earth biosphere. 32

Thermophiles Living around Hot Springs, Geysers, and Fumaroles

A thermophile is an organism—a type of extremophile—that thrives at high temperatures between 106 and 252 °F.  Thermophiles are usually microbes, and many are archaea. Thermophiles are found in the decaying plant matter of peat bogs and compost.

Hyperthermophiles are inhabitants of hot, sulfur-rich environments usually associated with volcanism, such as the hot springs, geysers, and fumaroles of Yellowstone Park. Hyperthermophiles isolated from hot springs in Yellowstone National Park were first reported by Thomas D. Brock in 1965. Since then, more than 70 species have been established. Many of the hyper-thermophilic Archaea require elemental sulfur for growth, including anaerobes that use the sulfur instead of oxygen as an electron acceptor during cellular respiration.

Research has shown that some minerals can catalyze the stepwise formation of hydrocarbon tails of fatty acids from hydrogen and carbon monoxide gases—gases that may have been released from hydrothermal vents or geysers. Since vesicle (lipid sphere) formation requires a higher concentration of fatty acids, some scientists suggest that protocell formation started at land-bound hydrothermal vents such as geysers, mud pots, and fumaroles where water evaporates and concentrates the solution. 33

Thermophiles and hyperthermophiles demonstrate how hardy life can be, and they imply that life can arise on other planets that are not in Earth’s so-called “Goldilocks Zone” of moderate temperatures and pressures. (For more, see: the Wikipedia article, Extremophile.)

  1. The Deep-Sea Model of First Life

Today, many thermophile and hyperthermophile microbes flourish in and around the hot volcanic vents at the bottoms of our deepest oceans, where Earth’s tectonic plates meet. They form large microbial communities surrounding these undersea vents, making them the primary food source for an entire food chain of more complex multi-cellular creatures, including shrimp and giant tube worms that can be up to 6 feet tall. Many scientists hold that life began in and around these deep-sea hydrothermal vents.

“Black Smokers”

We’ve said that organisms that do chemosynthesis can use inorganic electron donor sources such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia or organic sources.

“Black Smokers,” formally known as Hydrothermal Vents, were first discovered in 1979 on the East Pacific Rise, which is the main tectonic plate boundary the runs down the middle of the South Pacific Ocean, and then curves west almost to the tip of India.  34

The most extreme thermophiles, hyperthermophiles, live on the superheated walls of deep-sea hydrothermal vents, requiring temperatures of at least 194° Fahrenheit for survival. An extraordinary heat-tolerant hyperthermophile is “Strain-121,” has been able to double its population during 24 hours in an autoclave at 121 °C (hence its name). 35

The deep-sea organisms discovered around these hydrothermal vents have no access to sunlight, and no hope of doing photosynthesis. Instead, the diverse ecological communities surrounding these vents depend on nutrients found in the dusty chemical deposits and hydrothermal fluids thrown up by the undersea vents. Compared to the surrounding sea floor, however, these communities have a density of organisms 10,000 to 100,000 times greater than the surrounding ocean floor.

Biological Communities Around Deep-sea Vents

The chemotrophic bacteria around the deep-sea vents grow into a thick mat which attracts other organisms, such as shrimp-like amphipods and copepods, which graze upon the bacteria. Larger organisms, such as snails, clams, limpets, shrimp, crabs, tube worms, sea snails, slugs, fish (especially eelpout and cutthroat eel), and octopuses form a food chain of predator and prey relationships above the primary consumers.

Giant Tube Worms, which may grow to over 6.6 ft tall in the largest species, often form an important part of the community around a hydrothermal vent. They have no mouth or digestive tract, and like parasitic worms, absorb nutrients produced by the bacteria in their tissues. About 285 billion bacteria are found per ounce of tubeworm tissue. Tubeworms have red plumes which contain hemoglobin. Hemoglobin combines with hydrogen sulfide and transfers it to the bacteria living inside the worm. In return, the bacteria nourish the worm with carbon compounds.

36

Over 300 new species, including microbes and multicellular animals, have been discovered at hydrothermal vents, including more than 100 gastropod species (sea snails and slugs). 37

The ecological communities around deep-sea vents can sustain such vast amounts of life because at the bottom of the communal food chain are large populations of chemotrophic bacteria that consume water from the hydrothermal vents that is rich in dissolved minerals. A large population of bacteria consumes the sulfur compounds in that water, particularly hydrogen sulfide (a chemical highly toxic to most known organisms) and uses chemosynthesis to produce abundant organic material.

Undersea hydrothermal vents are now often found near volcanically active places, areas where tectonic plates are moving apart at spreading centers, ocean basins, and hotspots. Black smokers (as well as related white smokers) are now known to exist in the Atlantic and Pacific Oceans, at an average depth of 2100 meters. The most northerly black smokers are a cluster of five named Loki’s Castle, discovered in 2008 on the Mid-Atlantic Ridge between Greenland and Norway. 38

Active hydrothermal vents are thought to exist on Jupiter’s moon Europa, and Saturn’s moon Enceladus, and it is speculated that ancient hydrothermal vents once existed on Mars. 39

Biology Has Chemosynthesis and Photosynthesis.  What About “Thermosynthesis?”

Did the microorganisms growing around under-sea hydrothermal vents ever use thermosynthesis, i.e., the heat from those vents, to drive their constructive metabolism?  While there is little concrete evidence of this, Professor Anthonie Muller at the University of Amsterdam has proposed a theoretical mechanism (a model) by which this could have taken place. The components of the biological thermosynthesis machinery would be related to today’s process of ATP synthesis. It also resembles the process by which organic molecules adhere to the surfaces of clay crystals.

Muller proposes that this simple type of energy conversion may have sustained the origin of life, including the emergence of the RNA World. Thermosynthesis also permits, theoretically, a simple model for the origin of photosynthesis. However, no organisms are known at present that use thermosynthesis as a source of energy. 40

Deep-Sea “Iron-Eaters”

In the deep oceans, there are also iron-oxidizing bacteria that derive their energy needs by oxidizing ferrous iron (Fe2+) to ferric iron (Fe3+). (See Wikipedia on Panspermia.)

  1. The Panspermia Model of First Life 

The discovery of under-sea chemosynthesis revealed that terrestrial life, life on planet Earth, need not be sun-dependent; it only requires water and an energy gradient in order to exist. 41

In addition, the discovery of deep-sea ecosystems, along with advancements in the fields of astrobiology, observational astronomy, and discovery of large varieties of extremophiles, opened up a new avenue in astrobiology by massively expanding the number of possible extraterrestrial habitats; and also the possible transport of hardy microbial life through vast distances. 42

Note: This section of our Essay is largely paraphrased from the Wikipedia article Panspermia, as it appeared in February 2021. The footnotes citing that article’s sources are included at the end of this Essay.

“The chemistry leading to life may have begun shortly after the Big Bang, 13.8 billion years ago, during a habitable epoch when the Universe was only 10 to 17 million years old. Though the presence of life has been confirmed only on the Earth, some scientists think that extraterrestrial life is not only plausible, but probable or inevitable. 43

“From the early 1970s, it started to become evident that interstellar dust included a large component of organic molecules. Interstellar molecules are formed by chemical reactions within sparse interstellar or circumstellar clouds of dust and gas. The dust plays a critical role in shielding the molecules from the ionizing effect of ultraviolet radiation emitted by stars. 44

“The Panspermia Model of First Life is the hypothesis that life exists throughout the Universe, distributed by space dust, meteoroids, asteroids, comets, and planetoids. Distribution may have occurred spanning galaxies, and so may not be restricted to the limited scale of solar systems. 45

“Although computer models suggest that a captured meteoroid would typically take some tens of millions of years before collision with a planet, there are documented viable Earthly bacterial spores that are 40 million years old that are resistant to radiation, and others able to resume life after being dormant for 100 million years, suggesting that lithopanspermia life-transfers are possible via meteorites exceeding 1 m in size.46

“Conditions similar to those of the Miller–Urey experiments are present in other regions of the solar system, often substituting ultraviolet light for lightning as the energy source for chemical reactions. The Murchison meteorite that fell near Murchison, Victoria, Australia in 1969 was found to contain over 90 different amino-acids, nineteen of which are found in Earth life. 47

“Comets and other icy outer-solar-system bodies are thought to contain large amounts of complex carbon compounds (such as tholins) formed by these processes, darkening the surfaces of these bodies. We know the early Earth was bombarded heavily by comets, possibly providing a large supply of complex organic molecules along with the water and other volatiles the comets contributed.” 48

A 2017 paper from McMaster University in Canada and the Max Planck Institute in Germany showed that the building blocks of RNA could have polymerized in the early Earth using organic molecules from meteorites and interplanetary dust in shallow ponds. The wet/dry cycle of these ponds, they showed, was conducive to RNA polymerization. 49

In January 2018, a study (See https://en.wikipedia.org/wiki/Earliest_known_life_forms) found that 4.5 billion-year-old meteorites found on Earth contained liquid water along with prebiotic complex organic substances that may be ingredients for life. 50

Looking Ahead to Our Uwritten Essay, THE RISE OF MULTI-CELLULAR LIFE

In a sequel Essay, likely to be named “The Rise of Multicellular Life,” we will talk about the significant evolutionary events that happened relatively soon after the early single-celled archaea and bacteria had a good foothold on Earth.

For the first time, we have a fossil record to document many of organisms that evolved. For example, we see a fossil record of large bacterial colonies called “mats,” and we have clear evidence of the silica shells left by the diatoms (a species of single-celled protists).

Here is a partial list of the topics we expect to cover in our future Essay, “The Rise of Multicellular Life:”

  • Evolution of whiptails on bacteria: greater motility
  • The formation of colonies, including some very extensive “mats” of microbes and algae floating on surface waters.
  • The engulfment of some microbes by other larger microbes, with the captured organisms becoming what we now call organelles, including the cell nuclei, mitochondria and chloroplasts. These enclosures provide the host cell with specialized functions and assume a symbiotic relationship with the host.
  • Evolution of Eukaryotes
  • The cyanobacteria almost single-handedly create Earth’s oxygenated atmosphere
  • The slime mold: How a single-celled creature can evolve amazing capabilities
  • Networks of transport and communication within colonies.
  • The specialization of cells within a colony
  • The specialization of cells within an organism
  • Photosynthesis among algae and true plants
  • Form changes over life cycles.
  • Sexual Reproduction: Acceleration of Evolution

 ——————————————————————————————————————-

 

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  2. Wikipedia article on “Panspermia,” particularly footnotes 163 through 169.
  3. Wikipedia article on “Panspermia,” particularly footnotes 171 through 173.
  4. Jurassic Park, motion picture, 1993, Amblin Entertainment, Universal Studios; Dr. Malcolm was played by Jeff Goldblum;, after the 1990 novel of the same name by Dr. Michael Crichton.
  5. https://www.encyclopedia.com/science/science-magazines/did-life-earth-begin-little-warm-pond.
  6. https://www.encyclopedia.com/science/science-magazines/did-life-earth-begin-little-warm-pond.
  7. Martha Henriques, “The Idea that Life Began as Clay Crystals Is 50 Years Old” 8-24-2016, BBC.
  8. W. Martin and M. Russell, “On the Origins of Cells: A Hypothesis for the Evolutionary Transitions from Abiotic Geochemistry to Chemoautotrophic Prokaryotes, and “From Prokaryotes to Nucleated Cells,” Philosophical Transactions of the Royal Society, B, published online at Nature.com. doi:10.1098/rstb.2002.1183 (2002). https://www.nature.com/news/2002/021202/full/news021202-2.html.
  9. John Whitfield, “New Theory for Origin of Life: Mineral Cells Might Have Incubated First Living Things,” Nature, 12-4-2002, doi:10.1038/news021202-2. See also, N. Roldane, N. Hollinsworth, et al., “Bio-inspired CO2 Conversion by Iron Sulfide Catalysts Under Sustainable Conditions,” Royal Society of Chemistry, 3-24-15. https://pubs.rsc.org/en/content/articlehtml/2015/cc/c5cc02078f.
  10. D. Luo, D. Yang, S. Peng, and G.Q. Lu, “Enhanced Transcription and Translation in Clay Hydrogel and Implications for Early Life Evolution,” Scientific Reports, 11-7-2013; https://www.nature.com/articles/srep03165.
  11. Paraphrased from Bill Steele’s article, “Before Cells, Biochemicals May Have Combined in Clay,” 11-7-2013, Cornell Chronicle, Cornell University.
  12. Bill Steele, Ibid.
  13. Bill Steele, Ibid.
  14. Martha Henriques, “The Idea that Life Began as Clay Crystals is 50 Years Old,” 8-24-2016, BBC.
  15. Leslie March, “Life’s Crystal Code,” 3-19-2009, www.space.com.
  16. https://sites.google.com/site/originsoflifecarlmont/clay-theory. See also Martha Henriques, “The Idea that Life began as clay crystals in 50 years old, 8-24-2016, BBC.
  17. Leslie Mullen, “Life’s Crystal Code,” www.space.com.
  18. Arvin Ash, “Abiogenesis,” a video film, Ibid.
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  20. Leslie Mullen, “Life’s Crystal Code,” www.space.com]
  21. Martha Henriques, Ibid.
  22. Michael Schirber, “Diamonds May Be Life’s Birthstone,” Space.com, 9-25-2008,  https://www.space.com/5882-diamonds-life-birthstone.html.
  23. Michael Schirber, Ibid.
  24. Michael Schirber, Ibid.
  25. Leslie Mullen, “Life’s Crystal Code,” www.space.com, 3-19-2009.]
  26. Robert Hazen, Ibid., p.138.
  27. Leslie Mullen, “Life’s Crystal Code,” www.space.com, 3-19-2009.
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  32. F. Puente-Sanchez, A. Arce-Rodrigues, et al., Viable Cyanobacteria in the Deep Continental Subsurface, Proceedings of the National Academy of Sciences, 10-1-2018, https://www.pnas.org/content/115/42/10702. From Wikipedia, “Earliest Known Life Forms.”
  33. Carl Zimmer, “What Came Before DNA,?” Discover Magazine, 6-26-04.
  34. Sean Chamberlin, “Black Smokers and Giant Worms,” 1999, Fullerton College, Retrieved 2-11-2011. See also, Brent C. Christner, 2002, “Detection, Recovery, Isolation, and Characterization of Bacteria in Glacial Ice and Lake Vostok Accretion Ice,” 2002, Ohio State University.
  35. Office of Legislative Affairs, “Microbe from Depths Takes Life to Hottest Known Limit,” 8-14-2003, National Science Foundation, https://www.nsf.gov/od/lpa/news/03/pr0384.htm.
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  38. Live Science Staff, “Boiling Hot Water Found in Frigid Arctic Sea,” LiveScience, https://www.livescience.com/9588-boiling-hot-water-frigid-arctic-sea.html.
  39. Kenneth Chang, “Conditions for Life Detected on Saturn Moon Enceladus,” 4-13-2017, New York Times. See also, “Spacecraft Data Suggest Saturn Moon’s Ocean May Harbor Hydrothermal Activity,” NASA, 3-11-2015. See also, M. Paine, “Mars Explorers to Benefit from Australian Research,” 5-15-2001, Space.com. Both references from Wikipedia article, “Hydrothermal Vent.”
  40. For 19 separate footnote references to Dr. Muller’s scientific papers on this topic, see the Wikipedia article on Thermosynthesis.
  41. See the Wikipedia article, “Panspermia.”
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  43. From Wikipedia article on “Panspermia.”
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  45. Seth Shostak, “Comets and Asteroids May Be Spreading Life Across the Galaxy – “Are Germs From Outer Space the Source of Life on Earth,?” 10-26-2018, NBC News. See also, Idan Ginsburg, M. Lingham, and Abraham Loeb, “Galactic Panspermia,” 11-19-2018, The Astrophysical Journal Letters. 868 (1): L12. arXiv:1810.04307v2. Bibcode:2018ApJ…868L..12G.
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