All About Emergence

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A swarm of birds act as an emergent whole as opposed to a collection of individual birds. The workings of swarms have been fruitfully studied by artificial life scientists, who look for abstracted insights into life via computers and other techniques. (Walerian Walawski)

 

If there was a simple meaning of the often-used scientific term “emergence,” then 100-plus scientists wouldn’t have spent four days presenting, debating and not infrequently disagreeing about what it was.

But as last month’s organizers of the Earth-Life Science Institute’s “Comparative Emergence” symposium in Tokyo frequently reminded the participants, those debates and disputes are perfectly fine and to be expected given the very long history and fungibility of the concept.

At the same time, ELSI leaders also clearly thought that the term can have resonance and importance in many domains of science, and that’s why they wanted practitioners to be exposed more deeply to its meanings and powers.

Emergence is a concept commonly used in origins of life research, in complexity and artificial life science; less commonly in chemistry, biology, social and planetary sciences; and — originally – in philosophy. And in the 21st century, it is making a significant comeback as a way to think about many phenomena and processes in the world.

So what is “emergence?” Most simply, it describes the ubiquitous and hugely varied mechanisms by which simple components in nature (or in the virtual or philosophical world) achieve more complexity, and in the process become greater than the sum of all those original parts.

The result is generally novel, often surprising, and sometimes most puzzling – especially since emergent phenomena involve self-organization by the more complex whole.

Think of a collection of ants or bees and how they join leaderless by the many thousands to make something – a beehive, an ant colony – that is entirely different from the individual creatures.

 

The Eagle nebula is an intense region of star formation, an emergent phenomenon
that clearly creates something novel out of simpler parts. (European Space Observatory.)

Think of the combination of hydrogen and oxygen gases which make liquid water. Think of the folding of proteins that makes genetic information transfer possible. Think of the processes by which bits of cosmic dust clump and clump and clump millions of times over and in time become a planetesimal or perhaps a planet. Think of how the firing of the billions of neurons in your brain results in consciousness.

All create complexity out of component parts, produce something irreducible from those original parts, and all have been resistant to a full explanation using the usual reductionist tools of the scientific world. This doesn’t mean that something magical or divine is going on – rather, that either humans have not figured out what happens or that what happens is not comprehensible given our understanding of the laws of nature and physics.

Luis Campos is a historian of science and was Baruch S. Blumberg NASA/Library of Congress Chair in Astrobiology. (University of New Mexico)

Heady stuff, which is why the study and use of the concept of emergence has become increasingly widespread as a tool, or perhaps a pathway, to address complex problems.

Before going on, a little history is in order. Luis Campos, a historian of science at the University of New Mexico and the most recent Baruch S. Blumberg NASA/Library of Congress Chair in Astrobiology, described the concept of philosophical and scientific emergence – though not the word — as going back to the Greeks, at least.

The term “emergence” comes from the Latin verb emergo which means to arise, to rise up. Its meaning and importance have ebbed and flowed, with a major flowering in the United Kingdom in the 1920s.

It is seldom discussed, Campos said at the ELSI symposium, but the modern concepts of emergence flow to some extent from dialectics of Hegel, Marx and Engels, as well as the holism of South Africa’s controversial leader and thinker, Jan Smuts.

Campos said the “emergence” of today is quite different from those iterations. His point, he said, is that major scientific approaches grow from the societal bedrock of their times – and today that means a willingness to consider possible limits to the strict scientific reductionism of the modern era.

In philosophical terms, and generally in the history of science, there are several basic forms of emergence.

The first involves surprising complexity that arises unexplained and remains so at a particular scale, though science may catch up some day and provide plausible explanations. The formation of stars and galaxies and black holes would all be considered emergent phenomena, but astrophysics is gradually learning many of the processes that allow immeasurable complexity to appear throughout the cosmos – all from the simplest of components.

The other involves complex phenomena that appear to be beyond the capacity of physical or natural laws to ever explain. The quantum world, for instance, includes the phenomenon called quantum entanglement – a physical sensation which occurs when

The endlessly different symmetrical and fractal patterns of snowflakes are an emergent phenomenon given that each starts with the same basic material and ends up looking different. (Wilson Bentley)

pairs or groups of particles cannot be described independently of the state of the other, even when the particles are separated by a large distance.

So while emergence may be, as information scientist Francis Heylighen of the Vrije Universiteit in Brussel argued at the ELSI symposium, “simple, common and natural,” it also comes in innumerable forms that can seem mysterious or, as described in the quantum world, “spooky.”

David Pines, a co-founder of the Santa Fe Institute, which specializes in complexity studies, illustrated the dimensions of the emergence debate when he wrote about it several years ago for the online publishing site “Medium.”

“We live in an emergent universe,” he wrote, “in which it is difficult, if not impossible, to identify any existing interesting scientific problem or study any social or economic behavior that is not emergent.”

In the presence of claims like this, emergence has become a phenomenon where scientific consensus – or even agreement – can be difficult to achieve. Is it a trite “buzzword,” as some argue?  Or is it a profound and important pathway to understand underlying phenomena of the world that cannot be adequately described by reductionist, deterministic science?

Some of the modern pioneers in thinking about emergence come from the world of Artificial Life, or ALife. Using computer simulations, ALife researchers study essential properties of living systems such as evolution and adaptive behavior. Since the evolutionary clock cannot go backwards to see the what attributes are inevitable and what is more random, ALife analyzes these kinds of processes by simulating lifelike behaviors and patterns within computers.

As described at the ELSI symposium by University of Tokyo ALife and complex systems specialist Takashi Ikegami, decades of work in the ALife field have led to the conclusion that the pathways to life and consciousness are created by a cascade of emergent phenomena possessing the capability for “open-ended evolution.”

 

Takashi Ikegami and an android he helped build as part of his decades of work in the field of Artificial Life. (Bloomberg News)

 

And with computing power still increasing steadily, he said that the scale at which emergent properties can be identified and traced will similarly increase. As an example of how faster and larger computers can and will scale up ALife experiments and research, he told the story of the Rubik’s cube and what became known as “God’s algorithm.”

For 30 years, mathematicians and others working to solve the famous cube puzzle concluded that the minimum number of moves needed to complete the task was 22. This was not based on the experience of some Rubik’s cube fans, but rather of sustained mathmatical analysis.

But then in 2010 a teams of computer scientists and mathemeticians with access to Google’s supercomputers found that the minimum number of moves for any of the 43 quadrillion Rubik’s position was actually a very surprising 20. This result, Ikegami argues, is a reflection of the emergence of new technological capabilities in the last decade that are changing the world.

Some other classic artificial life simulations involve virtual birds or fish that are given some very simple rules to follow about how close individuals can approach each other and how they should steers in relation to other flock or schoolmates. Those simple instructions lead to the formation of virtual swarms and schools of enormous complexity that emerge from the individual-to-group transition.

An example of the unexpected behavior that can emerge: A flock splits to avoid an obstacle and then reunite once passed.

ALife is virtual, but emergence is everywhere in the natural world as well once you know what to look for. Bénard cells, for instance, are geometrically regular convection structures that spontaneously form in water or other thicker fluids when it is heated from below and/or cooled from above.

 

Benard cells formed spontaneously by convection in fluids.

The cells are formed as the hotter fluid rises and the cooler sinks, a process that results in spontaneous self-organization into a regular pattern of cells. The cells would be considered to be emergent phenomena.

John Hernlund is a geophysicist and vice director ELSI, and was the lead science organizer for the conference.

“Bénard convection is a composite phenomenon that arises from the combination of simpler processes: thermal expansion, Archimedes principle, thermal conduction, and viscous resistance to shearing motion in a fluid,” he said. “Nothing about those basic constituent processes alone would enable you to predict that their combination would yield the beautiful regular geometric patterns seen in Bénard cells, and this is why these are often used as an example of emergent behavior.”

Astrophysicist Elizabeth Tasker, a professor and communicator for the Japanese Space Agency JAXA, chaired an early session on emergence which focused on how the universe and planets were formed. She said her field has generally not described that 13.7 billion year process that followed the Big Bang in terms of emergent phenomenon, but that over the week she gradually saw the usefulness and did so in particularly compelling terms.

“As an astrophysicist,” she said. “I began to see the history of the universe as a manga, with examples of emergence forming the individual frames: matter strewn around the cosmos was drawn by gravity into structures that became galaxies, gas collapsed until fusion birthed a star, rocky boulders accreted and then began to melt and circulate to produce plate tectonics.

“Each manga frame represented the introduction of a new property of the universe, one that could not be exhibited by the individual pieces that had created it. A lone gas molecule could not show the spinning spiral of a galactic disc, nor begin to fuse elements within a star. Likewise, the rocky pieces that formed a planet could not start the circulation of plate tectonics by themselves. Neighboring interactions created a system that could spawn an entirely new process.”

While emergence is most often understood in terms of physical systems, and then virtual systems that try to capture their patterns and laws, the concept also has a presence in the social and economic sciences as well.

Alex Penn of the University of Surrey, in fact, introduced emergence in the social spheres and humanities as emergent on a scale similar to what Daniel Pines said about science. “Basically, almost everything of significance that arises in the social world is emergent,” she said.

Those phenomena ranged from the rise of different kinds of economic levels of development to political movements, cultures and down to the raising of children and residential segregation.

That housing segregation has been studied sufficiently that it has been determined that when a self-identifying group becomes less than one-third of the neighborhood population, they will begin to move to move out to be closer to those they identify with. Within a relatively short period of time, a mixed neighborhood will emerge into a segregated community via self-organization.

 

The Schelling model of what happens as neighborhoods self-segregate.

 

Other examples of emergence put forward from the social and cultural worlds include traffic jams, improv jazz performances and marriage. (A married person remains themselves, but also become part of a larger and more complex entity, from which novelty and surprise are sure to arise.)

Since the emergence symposium was taking place at an institute focused on how our planet formed and how life later appeared, it was only natural that emergence in that realm was a frequent topic. How a world without biology became one with biology is emergence writ large, with simplicity transforming to complexity innumerable times in innumerable ways.

While scientists speak of the Last Universal Common Ancestor (LUCA) as the source from which all life today arose, it is also widely held that other proto-life existed and disappeared because it could not compete successfully.

The ELSI model of that process is often presented as a kind of hourglass, where evolution of all kinds — in minerals, in prebiotic polypeptides, in simple organisms – creates new systems that take over and expand until they reach a bottleneck that stops the advance. Only a newly evolved version of the entity can make it through to the next step.

Participants including evolutionary biologist Simonetta Gribaldo of the Institut Pasteur argued that there is good reason to conclude that these processes were playing out wherever they could on the early Earth, doubtless resulting in many versions of prebiotic and proto-life before the Last Universal Common Ancestor (LUCA). In other words, the path to and beyond LUCA was not only messy but had many failed efforts along the way.

It fell to geochemist and geomicrobiologist Karyn Rogers of Rensselaer Polytechnic Institute to put it all into the context of emergence.

Long active in origin of life science, she said that she has become very uncomfortable with that description of what the field is trying to understand. Like many others, she does not see the “origin of life” as a singular phenomenon and so she moved to “origins of life.”

But “origins,” too, didn’t seem right because it seemed to focus too narrowly on the compounds and processes directly associated with life. She (and others) saw a larger picture.

Rogers said she doesn’t think scientists can talk about how biology appeared and prospered without also talking about the the mineral and geochemical world from which it arose.

Her conclusion, then, about how to describe what happened on prebiotic Earth so long ago:

Karyn Rogers’ research focuses on the relationships between microbial communities and environmental conditions in extreme ecosystems.  (Rensselaer Polytechnic Institute)

“It’s the emergence of life,” she said at the end of the symposium, not the “origin”.

“One of interesting things about emergence is that it’s that smudgy place in between that we can’t quite describe. We know it’s necessary to go from an abiotic planet to a biotic planet, but can’t quite really wrap our minds on it.

“It’s not even a series of events, it’s a series of events that led to life plus all the stuff around it as well that didn’t lead to life…all the surrounding processes. I think you need all that for life to emerge.”

She said she came into the symposium convinced that the “emergence of life” was the way to see the our biological beginnings, but that hearing about the many other understandings of emergence led her to think she didn’t understand the concept and would have to revise her views. But by the end she was back to emergence, but with a difference.

Perhaps, she said, the group could consider having “emergence” and “smudginess” become synonyms for that cross-discipline arena of simple-to-significantly more-complex transitions they had been discussing all week.

The idea was embraced by many of the other scientists.

 

A Livestream of the symposium is available here.

 

 

 

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The Moon-Forming Impact And Its Gifts

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Rice University petrologists have found Earth most likely received the bulk of its carbon, nitrogen and other life-essential volatile elements from the planetary collision that created the moon more than 4.4 billion years ago. (Rice University)

 

The question of how life-essential elements such as carbon, nitrogen and sulfur came to our planet has been long debated and is a clearly important and slippery scientific subject.

Did these volatile elements accrete onto the proto-Earth from the sun’s planetary disk as the planet was being formed?  Did they arrive substantially later via meteorite or comet?  Or was it the cataclysmic moon-forming impact of the proto-Earth and another Mars-sized planet that brought in those essential elements?

Piecing this story together is definitely challenging,  but now there is vigorous support for one hypothesis — that the giant impact brought us the elements would later be used to enable life.

Based on high pressure-temperature experiments, modeling and simulations, a team at Rice University’s Department of Earth, Environmental and Planetary Sciences makes that case in Science Advances for the central role of the proto-planet called Theia.

“From the study of primitive meteorites, scientists have long known that Earth and other rocky planets in the inner solar system are volatile-depleted,” said study co-author Rajdeep Dasgupta. “But the timing and mechanism of volatile delivery has been hotly debated. Ours is the first scenario that can explain the timing and delivery in a way that is consistent with all of the geochemical evidence.”

“What we are saying is that the impactor definitely brought the majority supply of life-essential elements that we see at the mantle and surface today,” Dasgupta wrote in an email.

 

A schematic depicting the formation of a Mars-sized planet (left) and its differentiation into a body with a metallic core and an overlying silicate reservoir. The sulfur-rich core expels carbon, producing silicate with a high carbon to nitrogen ratio. The moon-forming collision of such a planet with the growing Earth (right) can explain Earth’s abundance of both water and major life-essential elements like carbon, nitrogen and sulfur, as well as the geochemical similarity between Earth and the moon. (Rajdeep Dasgupta; background photo of the Milky Way galaxy is by Deepayan Mukhopadhyay)

 

Some of their conclusions are based on the finding of a similarity between the isotopic compositions of nitrogen and hydrogen in lunar glasses and in the bulk silicate portions of the Earth.  The Earth and moon volatiles, they conclude, “have a common origin.”

Carbon, nitrogen and sulfur are deemed “volatile” elements because they have a relatively low boiling point and can easily fly off into space from planets and moons in their early growing stages.  A number of other life-important chemicals, including water, are volatiles as well.

The recent findings are grounded in a series of experiments by study lead author and graduate student Damanveer Grewal, who works in the Dasgupta lab.  Grewal gathered evidence to test the theory that Earth’s volatiles arrived when the embryonic planet Theia — that had a sulfur-rich core — crashed into very early Earth.

The sulfur content of the donor planet’s core matters because of the puzzling evidence about the carbon, nitrogen and sulfur that exist in all parts of the Earth — other than the core.  The team needed to test the conditions under which a core with sulfur could, in effect, exclude other volatiles, thus making them more common in the planet’s mantle and above — and as a result more available to a planet it might crash into.  

The high temperature and pressure tests led to a computer simulation to find the most likely scenario that produced Earth’s volatiles. Finding the answer involved varying the starting conditions, running approximately 1 billion scenarios and comparing them against the known conditions in the solar system today.

 

Carbonaceous chondrites include some of the most primitive known meteorites, including the iconic Allende meteorite. Some scientists have proposed they delivered volatiles to Earth, but this latest paper disputes that conclusion.

“What we found is that all the evidence — isotopic signatures, the carbon-nitrogen ratio and the overall amounts of carbon, nitrogen and sulfur in the bulk silicate Earth — are consistent with a moon-forming impact involving a volatile-bearing, Mars-sized planet with a sulfur-rich core,” Grewal said.

Another often-cited explanation about how Earth received its volatiles is the “late veneer” theory, which holds that volatile-rich meteorites, leftover chunks of primordial matter from the outer solar system, arrived after Earth’s core formed.

And while the isotopic signatures of Earth’s volatiles match these primordial objects, known as carbonaceous chondrites, the elemental ratio of carbon to nitrogen is off. Earth’s non-core material, which geologists call the bulk silicate Earth, has about 40 parts carbon to each part nitrogen, approximately twice the 20-1 ratio seen in carbonaceous chondrites. 

This led to their conclusion that the late veneer theory could not explain the conditions they had found.

Although the Rice team’s paper does not go in depth into the question of how water got to Earth, Dasgupta wrote that the team’s conclusion that the moon-forming impact brought with it other volatiles, “it is likely that the impactor would contain and bring some water too. This is especially likely because this impactor needs to form in part from oxidized carbonaceous chondritic materials (that is the condition our experiments simulated as well).

“So although we did not factor in matching the water budget in our model, it is entirely possible that this impactor brought Earth’s water budget too, if the proto-Earth was water-poor.”

 

A study by Rice University scientists (from left) Gelu Costin, Chenguang Sun, Damanveer Grewal (sitting), Kyusei Tsuno, and Rajdeep Dasgupta found Earth most likely received the bulk of its carbon, nitrogen, and other life-essential elements from the planetary collision that created the moon more than 4.4 billion years ago. The findings appear in the journal Science Advances. (Jeff Fitlow/Rice University)

 

Dasgupta, the principal investigator on a NASA-funded effort called CLEVER Planets that is exploring how life-essential elements might come together on distant rocky planets, said better understanding the origin of Earth’s life-essential elements has implications beyond our solar system.

“This study suggests that a rocky, Earth-like planet gets more chances to acquire life-essential elements if it forms and grows from giant impacts with planets that have sampled different building blocks, perhaps from different parts of a protoplanetary disk,” Dasgupta said.

“This removes some boundary conditions,” he said. “It shows that life-essential volatiles can arrive at the surface layers of a planet, even if they were produced on planetary bodies that underwent core formation under very different conditions.”

Dasgupta said it does not appear that Earth’s initial composition of bulk silicate, on its own,  could have attained the concentrations of those life-essential volatiles needed to produce our atmosphere and hydrosphere and biosphere.

This all has great implications for exoplanet studies, he said.  It means that “we can broaden our search for pathways that lead to volatile elements coming together on a planet to support life as we know it.”

CLEVER Planets is part of the Nexus for Exoplanet System Science, or NExSS, a NASA astrobiology research coordination network that is dedicated to the study of planetary habitability. CLEVER Planets involves more than a dozen research groups from Rice, NASA’s Johnson Space Center, UCLA, the University of Colorado Boulder and the University of California, Davis.

 

 

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Time-Traveling in the Australian Outback in Search of Early Earth

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This story was written by Nicholas Siegler, Chief Technologist for NASA’s Exoplanet Exploration Program at the Jet Propulsion Laboratory with the help of doctoral student Markus Gogouvitis, at the University of New South Wales, Australia and Georg-August-University in Gottingen, Germany.

 

These living stromatolites at Shark Bay, Australia are descendants of similar microbial/sedimentary forms once common around the world.  They are among the oldest known repositories of life.  Most stromatolites died off long ago, but remain at Shark Bay because of the high salinity of the water. (Tourism, Western Australia)

 

This past July I joined a group of geologists, geochemists, microbiologists, and fellow astronomers on a tour of some of the best-preserved evidence for early life.

Entitled the Astrobiology Grand Tour, it was a trip led by Dr. Martin Van Kranendonk, a structural geologist from the University of New South Wales, who had spent more than 25 years surveying Australia’s Pilbara region. Along with his graduate students he had organized a ten-day excursion deep into the outback of Western Australia to visit some of astrobiology’s most renowned sites.

The trip would entail long, hot days of hiking through unmaintained trails on loose surface rocks covered by barb-like bushes called spinifex.  As I was to find out, nature was not going to give up its secrets easily.  And there were no special privileges allocated to astrophysicists from New Jersey.

 

The route of our journey back in time.  (Google Earth/Markus Gogouvitis /Martin Van Kranendonk)

The state of Western Australia, almost four times the size of the American state of Texas but with less than a tenth of the population (2.6 million), is the site of many of astrobiology’s most heralded sites. For more than three billion years, it has been one of the most stable geologic regions in the world.

It has been ideal for geological preservation due to its arid conditions, lack of tectonic movement, and remoteness. The rock records have in many places survived and are now able to tell their stories (to those who know how to listen).

 

The classic red rocks of the Pilbara in Western Australia, with the needle sharp spinifex bushes in the foreground. (Nick Siegler, NASA/JPL-Caltech)

Our trip began with what felt like a pilgrimage. We left Western Australia’s largest city Perth and headed north for Shark bsy. It felt a bit like a pilgrimage because the next morning we visited one of modern astrobiology’s highlights – the living stromatolites of Shark Bay.

Stromatolites literally mean “layered rocks”. It’s not the rocks that are alive but rather the community of microbial mats living on top. They are some of the Earth’s earliest ecosystems.

We gazed over these living microbial communities aloft on their rock perches and marveled at their exceptional longevity — the species has persisted for over three billion years. Their ancestors had survived global mass extinctions, planet-covering ice glaciers, volcanic activity, and all sorts of predators. Once these life forms took hold they were not going to let go.

 

The stromatolites forming today in the shallow waters of Shark Bay, Australia are built by colonies of microbes that capture ocean sediments. (University of Wisconsin-Madison)

The photosynthetic bacteria that built ancient stromatolites played a central role of our trip for three reasons:

  • Their geological footprints allowed scientists to date the evolution of early life and at times gain insight into the environments in which they grew.
  • They eventually harbored the first oxygen-producing bacteria and played a central role in creating our oxygen-rich atmosphere.
  • By locating ever-increasingly older microbial fossils we observed a lower limit to the age of the first life forms.. Given photosynthesis is not a simple process, the first life forms must have been simpler. Speculating, perhaps a few hundred million years earlier so that the first life form on Earth may have originated at four billion years ago.

When viewed under a microscope, you can see the mats are made of millions of single cell bacteria and archaea, among the simplest life forms we know. Within these relatively thin regions are multiple layers of specialized microbial communities that live interdependently.

Bacteria in the top layer evolved to harvest sunlight to live and grow via photosynthesis. Their waste products include oxygen as well as important nutrients for many different bacterial species within underlying layers. And this underlying layer’s waste product would do the same for the layer beneath it, perfectly recycling each other’s waste. The oldest forms of life that we know of had learned to co-exist together in a chemically interdependent environment.

 

Broken piece of a living stromatolite, which was was remarkably spongy and smelled slightly salty, indicative of the hypersaline bay that has contributed to their survival by making bacteria and other organisms undesirable. What was actually most remarkable of the visit to Hamelin pool was how quiet it was. There were no seagulls and other birds because of the hypersaline environment. They had gone elsewhere for their meals. (Nick Siegler, NASA/JPL-Caltech)

 

We saw ripped up portions of the mats that washed upon the shore at Hamelin pool in Shark Bay. A whole ecosystem held in one’s hand. Thousands of millions of years ago ancient relatives of these microbes thrived in shallow waters all around our planet, and left behind fossilized remains. But due to the evolution of grazing organisms these microbial structures are nowadays constrained to very specific environments. In the case of Shark Bay, the very high salt contents of this inlet have warded off most predators providing the microbes with a safe haven to live.

Ironically, the rocks, which help identify these ancient life forms, at the time were just a nuisance for the living microbes.

Small fine grains of sedimentary rock carried along in the daily tides would occasionally get stuck in the sticky mucus the microbes would secrete. In addition, the photosynthetic bacteria found at Shark Bay may have been inadvertently making their own rock by depleting the carbon dioxide in the surrounding water as part of photosynthesis and precipitating carbonate, adding to the grains of sediment trapped within the sticky top layer.

Over time, the grains from both the sedimentary and precipitated rocks would  cover the surface and block the sunlight for which these organisms had evolved to depend on. As an evolutionary tour de force, the photosynthetic microbes learned to migrate upward, leaving the newly formed rock layers behind.

These secondary rock fossils today showcase visually observable crinkly, frequently conical shapes, in stark contrast to abiotic sedimentary rocks. These ancient life forms left behind geological footprints reminding us they were here first.

Nick Siegler of JPL on his Australian Magical Origins Tour.  (Markus Gogouvitis)

Now to the most important contribution of stromatolites – terraforming the Earth.

Living in shallow water, the top most layer of the Shark Bay microbial mats are known to host cyanobacteria, photosynthetic bacteria that produce oxygen as a byproduct. Scientists don’t know what the first bacteria produced as they harnessed the energy of the Sun. But they do know that they eventually started producing oxygen.

In the evolution of life that eventually led to all plants and animals, this was one of the great events. More than 2.5 billion years ago, ancient bacteria began diligently producing oxygen in the oceans. Earth’s atmosphere began to irreversibly shift from its original, oxygen-free existence, to an oxic one, initiating the formation of our ozone layer and paving the way for the evolution of more complex life. Our planet has been terraformed by micro-organisms!

It was in the Karijini National Park where we went back in time (2.4 billion years) and observed an extraordinary piece of evidence for the early production of oxygen in Earth’s oceans, a time before oxygen made a strong presence in our atmosphere.

 

Banded iron formation at Karajini National Park.  (Nick Siegler, NASA-JPL/Caltech)

 

We saw a massive gorge with steep vertical walls carved out by flowing water. As oxygen production by early bacteria increased below the water surface it would react with dissolved iron ions (early oceans were iron-rich) causing iron oxides to precipitate and settle to the bottom.

For reasons not entirely understood — perhaps related to seasonal or temperature effects– the amount of new oxygen temporarily decreased and iron ion remained soluble in the oceans and other types of sediments accumulated, carbonates, slate, and shale. And then, just as before, the oxygen reappeared creating a new layer of precipitated iron.

The result was a banded sedimentary rock, a litmus test to a changing world, where oxygen would be the reactive ingredient leading to larger and more complex life forms. As the oxygen production no longer cycled, the oxygen went on to saturate the ocean and then accumulated in the Earth’s atmosphere eventually to the levels we have today.

 

Banded iron formation at Karajini. (Nick Siegler, NASA-JPL/Caltech)

After a day of looking down at rocks and spinifex it was both a relief and a joy to look up at the glorious Western Australian night sky. Far away from the light pollution of modern cities, each night would greet us with an awe-inspiring starlit sky. It never got old to remember we are part of a vast network of stars suspended in an infinite space.

The nights would start with the appearance of Venus well before sundown followed shortly by the innermost planet Mercury and then Jupiter and Saturn. It didn’t take long after sunset to see the renowned Southern Cross. Mars joined the evening as well, perfectly appearing on the arc called the ecliptic.

But nothing stirred the group more than the emergence of the swath of stars of the Milky Way, the disk of our home galaxy where its spiral arms all lie. The nights would be so clear that one could actually see the dark clouds of gas and dust that block large portions of the galaxy’s stars from shining through. We partook in the well-known tradition connecting individual points of light to form exotic creatures like scorpions and centaurs. But we also we followed the inverted approach of the Aborigines and connected the dark patches. Only then did we see the emu of the Milky Way. I would never have thought of connecting the darkness.

 

Australian night sky, with campfire below.  (Maëva Millan/NASA-GSFC/Georgetown University)

The night sky appeared even more special knowing that each of its stellar members likely host planetary systems like our own. How many of them host life? Maybe even civilizations? The numbers are in their favor.

At the half-way point of our trip we hiked to an ancient granite region in the red rocks of the Pilbara which contain the world’s largest concentration of Pleistocene rock art also known as petroglyphs. These etchings are believed to be 6,000 to 20, 000 years old.

The artists used no pigments, but rather rocks to pound/chisel shapes into the desert varnish, a thin dark film (possibly of microbial origin) that typically covers exposed rock surfaces in hyper arid regions. We came across many stylized male and female figures with highlighted genitalia as well as animals such as emus and kangaroos. Little is known about the people who created these art works. They left no clues to their origin or fate.

 

Rock art by aboriginal people done 6,000 to 20,000 years ago. The shapes were etched into an existing varnish on the rock. (Nick Siegler, NASA-JPL/Caltech)

Pilbara is also where the oldest mineral on Earth –a zircon dated at 4.4 billion years old — was discovered four years ago in the Jack Hills region.  Because of the geological history of the region, it is a frequent (if hardscrabble) site where many geologists and geochemists specializing in ancient Earth do their work.

In the last several days of the tour we encountered ever-increasing older evidence of stromatolites extending out to circa 3.5 billion years, about 75% of the history of the Earth. I expected the quality of the stromatolites to degrade as we went back in time and it looked like I was right until I saw a remarkably large rock in a locality called the Strelley Pool Formation. The rock measuring approximately 1.5 meters in all three directions gave a rare view of ancient stromatolites from all sides and an unequivocal interpretation of past life.

Large and ancient fossil stromatolite at the Strelley Pool Formation, with Siegler and Gogouvitis.  (Nick Siegler, NASA-JPL/Caltech)

The shapes of the embedded rocks formed by the microbial mats from the top view clearly show the elliptical areas where the bacteria inched upwards to acquire sunlight. Regions between the conical stromatolites were filled in by carbonate sediments in ancient shallow waters. These were later chemically altered to silica-rich rocks through alteration and etching of minerals by fluids. Silicified rocks are very weather-resistant, making them a great medium to preserve fossils for billions of years.

The side views of the stromatolite-laden rock revealed the expected conical layered shapes we saw in younger rocks (and in the living stromatolites of Shark Bay). Everything we had learned about stromatolite structures was clearly visible in this circa 3.43 billion year old example. It is astounding to realize that complex phototrophic (light-eating) organisms, even if not yet oxygen producing, were around during the deposition of the Strelley Pool Formation.

 

Detail of Strelley Pool stromatolite fossil.  (Nick Siegler, NASA-JPL/Caltech)

It is not unreasonable to speculate that the earliest life forms are even older by perhaps a few more hundred million years or so. There is evidence for even more ancient stromatolites in Greenland (3.7 billion years old) and isotope carbon evidence, with considerable controversy, in Nuvvuagittuq greenstone belt in northern Quebec, Canada (4.28 billion years old). Hence, life on Earth may have emerged within 500 million years from its formation. That is astonishingly rapid.

Was Earth an exception or the rule? What does that say for possible life on exoplanets?

Our tour came to an end on July 11. We had traveled over 1,600 miles through Australia’s outback, from Western Australia’s biggest city Perth, all the way up to Port Hedland at the north coast. We were privileged to see the country in ways that very few people get a chance to, and to be steeped in the multidisciplinary sciences of astrobiology while seeing some of its iconic ground.

I had seen some of the earliest evidence for life and the pivotal effect it had on our environment. For those 10 days I learned what it was like to be a time traveler.

 

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Piecing Together The Narrative of Evolution

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A reconstruction of the frond-like sea creature Stromatoveris psygmoglena, which lived during the Cambrian explosion of life forms on Earth.  Newfound fossils of Stromatoveris were compared with Ediacaran fossils, and researchers concluded they were all very early animals and that this animal group survived the mass extinction event that occurred between the Ediacaran and Cambrian periods. (Jennifer Hoyal Cuthill.)

An essential characteristic of life is that it evolves. Whether on Earth or potentially Mars, Europa or distant exoplanets, we can assume that whatever life might be present has the capacity and the need to change.

Evolution is intimately tied to the origin-of-life question, which this column often explores.  Having more answers regarding how life might have started on Earth can no doubt help the search for life elsewhere, just as finding life elsewhere could help understand how it started here.

The connection between evolution and exoplanets has an added and essential dimension when it comes to hunting for signatures of distant extraterrestrial life.

Searching for a planet with lots of oxygen and other atmospheric compound in disequilibrium (as on Earth) is certainly a way forward. But it is sobering to realize that those biosignatures would not have been detectable on Earth for most of the time that life has been present.  That’s because large concentrations of oxygen are a relative newcomer to our planet,  product of biological evolution.

With all this in mind, it seems both interesting and useful to look at the work of a researcher studying the fossil record to better understand a particular transition on Earth — the one from simpler organisms to multicellular creatures that can be considered animals.

The surprising, large transitional life of the Ediacaran period, which just preceded the Cambrian explosion of complex life. This grouping is termed the Ediacara assemblage, and existed late in the period.  (John Sibbick)

The researcher is Jennifer Hoyal Cuthill of the University of Cambridge, who I first met at the Earth-Life Science Institute in Tokyo, a unique place where scientists research the origin of Earth and of life on Earth.

She had been included in a group of twelve two-year fellows recruited from around the world who specialized in fields ranging from the microbiology of extreme environments to the current and past dynamics of the deep Earth and the digital world of chemo informatics.  And then there was Hoyal Cuthill, whose field is paleobiology, with a heavy emphasis on evolution.

Now Hoyal Cuthill has published a paper in the journal Paleontology that describes findings in the fossil record that shed light on that transition from less complex organisms like bacteria, algae and fungi to  to animals.

Her specialty is the Ediacaran period some 635 to 541 million years ago.  This transitional period came after a snowball Earth event and was followed by the Cambrian explosion, when ocean life of all sorts grew and changed at an unprecedented rate.  But as she and others have found, the Ediacaran also had large and unique lifeforms, and she is working to make sense of them.

She described her work and findings more specifically as follows:

“When did animals originate? What were the bizarre, early fossils known as the Ediacaran biota?

“We show that both questions are answered by a frond-like sea creature called Stromatoveris psygmoglena known from exceptionally preserved, Cambrian fossils from Chengjiang County, China.

“Originally described from only eight specimens, we examined over 200 new fossils since discovered by researchers from Northwest University (in Xian.) Stromatoveris was compared to earlier Ediacaran fossils in a computer analysis of anatomy and evolutionary relationships.

“This showed that Stromatoveris and seven key members of the Ediacaran biota share detailed anatomical similarities, including multiple, radiating, branched fronds that unite them as a phylum of early animals, originating by the Ediacaran Period and surviving into the early Cambrian.”

Fossil of Stromatoveris psygmoglena, turned on its side.  New research suggests that Stromatoveris and related Ediacaran lifeforms could be among the earliest creatures that can be described as an animal. Ediacaran fossils have been found from Australia to arctic Siberia, Canada to southern Africa.  (Jennifer Hoyal Cuthill)

 

Dickinsonia is a genus of iconic fossils of the Ediacaran biota. While a bilaterian affinity had been previously suggested by some researchers, this study suggests that it is closely related to other members of the Ediacaran biota as well as Cambrian Stromatoveris.  (Jennifer Hoyal Cuthill)

 

More broadly, Hoyal Cuthill told me that “the story of the origin of life and the evolution of life are so interwoven.”

“Looking back as far as we can, we see important patterns emerging from the very start.  All things learn.  If possible, they add to complexity… And evolution does not result in a complete replacement.  When transitions happen -– even big ones – important life patterns continue.  And so do some creatures.”

This continuity within change is what she has focused on, in the transitional Proterozoic Eon when bacterial and plant life evolved into the more complex ocean animal life of the Cambrian explosion.

She has traveled the world and scoured the fossil record to come up with this conclusion:  that creatures that can be called “animals” existed at least as far back as the early days of the Ediacaran, some 630 million years ago, when many macro-fossils quite suddenly appeared following that early epoch of global freezing.

The Ediacaran period gets its name from the Ediacara Hills in Australia, where famous fossils of this age were found. Known also as the Vendian, the Ediacaran was the final stage of Pre-Cambrian time. During this time, large (up to meter-sized) organisms, often shaped like fronds with holdfast discs, lived on thick mats of bacteria which, unlike today, coated the sea floor. The slimy mats acted as a barrier between the water above and the sediments below, preventing oxygen from reaching under the sea floor and making it less habitable.

And then when the Cambrian explosion occurred beginning some 540 million years ago, most of those lifeforms were thought to have gone extinct. Some paleobiologists hold that Earth’s first mass extinction actually took place during this period, when newly evolved animals transformed the environment.

Biota from the Ediacaran period through the Cambrian explosion. (Proceedings of the Royal Academy; B M. Gabriela Mángano, Luis A. Buatois)

Hoyal Cuthill says that her research leads her to a very different view: that there was a broad but not mass extinction, and that Ediacaran animals survived well after the Cambrian Explosion.

And in the journal paper published this week, Hoyal Cuthill and co-author Jian Han of Northwest University in Xian present fossil evidence from southern China of Cambrian creatures that she argues are unquestionably animal.

She said they have characteristics such as radial symmetry, differentiated bodies and an animal type organization. These fossils date from the early Cambrian, she said, yet they are similar in important ways to creatures found during the earlier Ediacaran period.

In other words, this group of animals not only persisted from the onset of the Ediacaran period, but also after the often-invoked mass extinction that came along with the Cambrian Explosion.

Jennifer Hoyal Cuthill, paleobiologist with a focus on Ediacaran period when life began to grow substantially in size. (Julieta Sarmiento Photography).

Hoyal Cuthill says that while the fossil record from the Ediacaran is sparse, flora and fauna are known to have included some of the oldest definite multicellular organisms. The organisms, she said, resembled fractal fronds but bear little resemblance to modern lifeforms.

The world’s first ever burrowing animals also evolved in the Ediacaran, though we don’t know what they looked like. The only fossils that have been found are of the burrows themselves, not the creatures that made them.

In an earlier paper, she described how and why many of the Ediacaran lifeforms got as large as they did.

“All organisms need nutrients simply to survive and grow, but nutrients can also dictate body size and shape.

“During the Proterozoic, there seem to have been major changes in the Earth’s oceans which may have triggered this… growth to the macro-scale. These include increases in oxygen and, potentially, other nutrients such as organic carbon.”

In other words, the surrounding atmosphere, oceans, perhaps reversing magnetic fields, tectonic and volcanic activity and the resulting menu of chemical compounds available and climatic conditions are essential drivers of biological evolution.  Just as they are now considered some of the important indicators of a potentially habitable exoplanet.

And on a currently far more fanciful note, wouldn’t it be wonderful if scientists could some day not only find life beyond Earth, but to learn to study how that life, too, might have evolved.

 

 

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Diamonds and Science: The Deep Earth, Deep Time, and Extraterrestrial Crystal Rain

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Deep Earth diamond with garnet inside.  These inclusions, which occur during the diamond formation process, provide not only a way to date the diamonds, but also a window into conditions in deep Earth when they wee formed.  (M. Gress, VU Amsterdam)

We all know that cut diamonds sparkle and shine, one of the great aesthetic creations from nature.

Less well known is that diamonds and the bits of minerals, gases and water encased in them offer a unique opportunity to probe the deepest regions of our planet.

Thought to be some of the oldest available materials found on Earth — some dated at up to 3.5 billion years old — they crystallize at great depth and under great pressure.

But from the point of view of those who study them, it’s the inclusions that loom large because allow them to know the age and depth of the diamond’s formation. And some think they can ultimately provide important clues to major scientific questions about the origin of water on Earth and even the origin of life.

The strange and remarkable subterranean world where the diamonds are formed has, of course, never been visited, but has been intensively studied using a variety of indirect measurements.  And this field has in recent weeks gotten some important discoveries based on those diamond inclusions.

First is the identification by Fabrizio Nestola of the Department of Geosciences at the University of Padua and colleagues of a mineral that has been theorized to be the fourth most  common on Earth, yet had never been found in nature or successfully synthesized in a laboratory.  As reported in the journal Nature, the mineral is a variant of calcium silicate (CaSiO3), created at a high pressure that gives it a uniquely deep-earth crystal structure called “perovskite,” which is the name of a mineral, too.

Mineral science does not allow a specimen to be named until it has actually been found in name, and now this very common form of mineral finally will get a name. But more important, it moves forward our understanding of what happens far below the Earth’s surface.

 

 

Where diamonds are formed and found on Earth. The super-deep are produced very far into the mantle and are pushed up by volcanoes and convection  The lithospheric diamonds are from the rigid upper mantle and crust and the alluvial diamonds are those which came to the surface and then were transported elsewhere by natural forces. (Fabrio Nestola, Joseph R Smyth)

 

The additional discovery was of a tiny bit of water ice known as ICE-VII inside several other deep diamonds.  While samples of H2O ice have been identified in diamonds before, none were ICE-VII which is formed only under tremendous deep-Earth pressure.

In addition to being a first, the ICE-VII discovery adds to the growing confidence of scientists that much H2O remains deep underground, with some inferring as much deep subsurface water as found in the surface oceans.  That paper was authored by University of Nevada, Las Vegas geoscientist Oliver Tschauner and colleagues, and appeared in the journal Science.

Diamonds are a solid form of carbon with a distinctive cubic crystal structure.  They are generally formed at depths of 100 to 150 miles in the Earth’s mantle, although a few have come from as deep as 500 to 600 miles down.  (And some come from space, as described in this article below and in a just published Nature Communications article about diamonds in the Almahata Sitta meteorite that crashed in Sudan in 2006.)

Those super-deep Earth diamonds form in a cauldron up to 1,000 degrees F and at 240,000 times the atmospheric pressure at sea level.  They are made from carbon-containing fluids that dissolve minerals and replace them with what over time become diamonds.

Much more recently (tens to hundreds of million years ago), the would have been pushed to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites (blue-tinged in color and coarse grained) and lamproites (rich in potassium and also from deep in the mantle.)

The mantle – which makes up more than 80 percent of the Earth’s volume – is made of silicate minerals containing iron, aluminum, and calcium among others.  Blue diamonds are that color because of the presence of the trace mineral boron in the mantle.

And now we can add water the list as well.

 

Professor of Mineralogy Fabrizio Nestola presented on his recent work in advances in X-ray crystallography on diamonds and their inclusions in a talk title “Diamond, A Journey to the Center of the Earth.” One of his collaborators on the recent high-pressure calcium silicate paper is mantle geochemist Graham Pearson of the University of Alberta, where Nestola was recently a visiting professor. (RadioBue.it)

Nestola, who has been conducting his deep-Earth studies with a major grant from the European Union, is eager to take his already substantial work much further.

First he is looking for answers to the basic question of the origin of water on Earth (from incoming asteroids and comets or an integral component at formation) and ultimately to the origin of life.  Diamonds, he says, offer a pathway to study both subjects.

For water, his goal is to find a range of diamond-encircled samples that can be measured for their deuterium to hydrogen ratio — a key diagnostic to determining where in the solar system an object and its H2O originated,  Deuterium, or heavy hydrogen, is an isotope of hydrogen with an extra neutron.

An example of a super-deep diamond from the Cullinan Mine, where scientists recently discovered a diamond that provides first evidence in nature of Earth’s fourth most abundant mineral–calcium silicate perovskite. (Petra Diamonds)

As the number of diamond samples with evidence of water grows, Nestola says it will be possible to determine how the D/H ratio changes over time and as a result gain a better understanding of where the Earth’s water came from.

When it comes to clues regarding the origin of life, Nestola will be looking for carbon isotopes in the diamonds.

“Actually, it cannot be excluded that carbon from a primordial organic matter can even travel to the lower mantle,” he told me. “The oldest diamonds were dated 3.5-3.6 billion years, so it would be fantastic to detect a carbon isotope signature of surface carbon in a 3.5 billion years diamond.  This could provide very strong input for the origin of life.”

Regarding the high-pressure form of calcium silicate that he and his colleagues recently identified, Nestola said that many scientists have tried to reproduce it in their labs but have found there’s no way to keep the mineral stable at surface pressures.  So the discovery had to be made from inside the nearly impermeable container of a diamond.

The diamond that contained the common yet never before found mineral was just 0.031 millimeters across, is also a super-rare specimen.

Adding to the interest in this discovery is that other trace minerals and elements found in the inclusion strongly suggest that the material was once on the Earth’s crust.  The logic is that it would have been subducted as a function of plate tectonics billions of years ago, then encased in a forming diamond deep in the mantle, and ultimately sent back up near the surface again.

Most diamonds are born much closer to Earth’s surface, between 93 and 124 miles deep. But this particular diamond would have formed at a depth of around 500 miles, the researchers said.

“The diamond keeps the mineral at the pressure where it was formed, and so it tells us a lot about the ancient deep-Earth environment,” Nestola said.  “This is how we’ll learn about deep Earth and ancient Earth.  And we hope about those central origin questions too.”

 

A South African diamond crystal on kimberlite, an igneous rock formed deep in the mantle and famous for the frequency with which it contains diamonds. (Shutterstock)

For his ICE-VII study, Tschauner used diamonds found in China, the Republic of South Africa, and Botswana that had been pushed up from inside Earth.  He believes the range of locations strongly suggests that the presence of the ICE-VII is a global phenomenon.

Scientists theorize the diamonds used in the study were born in the mantle under temperatures reaching more than 1,000-degrees Fahrenheit.

“One essential question that we are working on is how much water is actually stored in the mantle.  Is it oceans, or just a bit?” Tschauner said. “This work shows there can be free excess fluids in the mantle, which is important.”

The mantle is a vast reservoir of mostly solid and very hot rock under immense pressure beneath the crust. It has an upper layer, a transition zone, and a lower layer. The upper layer has a little bit of water, but scientist estimate 10 times more water may be in the transition zone, where the enormous pressure is changing crystal structures and minerals seem to be more soluble. Minerals in the lower layer don’t seem to hold water as well.

There’s already evidence of water in the mantle in different forms, such as water that has been broken up and incorporated into other minerals. But these diamonds contain water frozen into a special kind of ice crystal. There are lots of different ways water can crystallize into ice, but ice-VII is formed under higher pressures.

While the diamond was forming, it must have encapsulated some liquid water from around the transition zone. The high temperatures prevented this water from crystalizing under the high pressures. As geologic activity moved the diamonds to the surface, they maintained the high pressures in their rigid crystal structures—but the temperature dropped. This would have caused the water to freeze into ice-VII.

The discovery of Ice-VII in the diamonds is the first known natural occurrence of the aqueous fluid from the deep mantle. Ice-VII had been found as a solid in prior lab testing of materials under intense pressure. As described before,  it begins as a liquid in the mantle.

“These discoveries are important in understanding that water-rich regions in the Earth’s interior can play a role in the global water budget and the movement of heat-generating radioactive elements,” Tschauner said.

This discovery can help scientists create new, more accurate models of what’s going on inside the Earth, specifically how and where heat is generated under the Earth’s crust.

 “It’s another piece of the puzzle in understanding how our planet works,” Tschauner said.

A polished and enlarged section of the Esquel pallasite meteoritemeteorite that delivered tiny nano-diamonds to Earth. This is a common occurrence, as there is believed to be substantial amounts of high-pressure carbon in the galaxies, and thus some diamonds. (Trustees of the NHM, London)

The diamonds studied by researchers such as Nestola and Tschauner not the sort that would ever go to the market.  “They are very bad diamonds, bad for jewelers,” Nestola said, “but precious for geologists.”

Diamonds are by no means exclusive to Earth, and are becoming a significant area of study for planetary exoplanet scientists, too.

Not only are they contained in minute form in meteorites, but atmospheric data for the gas giant planets indicates that carbon is abundant in its famous hard crystal form elsewhere in the solar system and no doubt beyond.

Lightning storms turn methane into sooty carbon which, as it falls, hardens under great pressure into graphite and then diamond.

These diamond “hail stones” eventually melt into a liquid sea in the planets’ hot cores, researchers told a an American Astronomical Society conference in 2013.

The biggest diamonds would likely be about a centimeter in diameter – “big enough to put on a ring, although of course they would be uncut,” says Dr Kevin Baines, of the University of Wisconsin-Madison and NASA’s Jet Propulsion Laboratory.

“The bottom line is that 1,000 tons of diamonds a year are being created on Saturn. People ask me – how can you really tell? Because there’s no way you can go and observe it.

“It all boils down to the chemistry. And we think we’re pretty certain.”

These potential raining diamonds, and all sorts of other extraterrestrial diamonds including possible diamond worlds, doubtless have their own scientifically compelling and important stories to tell.

 

 

 

 

 

 

 

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