Category: The Origin of Life (page 2 of 3)

All About Emergence

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.Read more

The Moon-Forming Impact And Its Gifts

 

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. Read more

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

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.… Read more

Piecing Together The Narrative of Evolution

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.… Read more

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

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.

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False Positives, False Negatives; The World of Distant Biosignatures Attracts and Confounds

This artist’s illustration shows two Earth-sized planets, TRAPPIST-1b and TRAPPIST-1c, passing in front of their parent red dwarf star, which is much smaller and cooler than our sun. NASA’s Hubble Space Telescope looked for signs of atmospheres around these planets. (NASA/ESA/STScI/J. de Wit, MIT)

What observations, or groups of observations, would tell exoplanet scientists that life might be present on a particular distant planet?

The most often discussed biosignature is oxygen, the product of life on Earth.  But while oxygen remains central to the search for biosignatures afar, there are some serious problems with relying on that molecule.

It can, for one, be produced without biology, although on Earth biology is the major source.  Conditions on other planets, however, might be different, producing lots of oxygen without life.

And then there’s the troubling reality that for most of the time there has been life on Earth, there would not have been enough oxygen produced to register as a biosignature.  So oxygen brings with it the danger of both a false positive and a false negative.

Wading through the long list of potential other biosignatures is rather like walking along a very wet path and having your boots regularly pulled off as they get captured by the mud.  Many possibilities can be put forward, but all seem to contain absolutely confounding problems.

With this reality in mind, a group of several dozen very interdisciplinary scientists came together more than a year ago in an effort to catalogue the many possible biosignatures that have been put forward and then to describe the pros and the cons of each.

“We believe this kind of effort is essential and needs to be done now,” said Edward Schwieterman, an astronomy and astrobiology researcher at the University of California, Riverside (UCR).

“Not because we have the technology now to identify these possible biosignatures light years away, but because the space and ground-based telescopes of the future need to be designed so they can identify them. ”

“It’s part of what may turn out to be a very long road to learning whether or not we are alone in the universe”.

 

Artistic representations of some of the exoplanets detected so far with the greatest potential to support liquid surface water, based on their size and orbit.  All of them are larger than Earth and their composition and habitability remains unclear. They are ranked here from closest to farthest from Earth. 

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2.5 Billion Years of Earth History in 100 Square Feet

Scalding hot water from an underground thermal spring creates an iron-rich environment similar to what existed on Earth 2.5 billion years ago. (Nerissa Escanlar)

Along the edge of an inlet on a tiny Japanese island can be found– side by side – striking examples of conditions on Earth some 2.4 billion years ago, then 1.4 billion years ago and then the Philippine Sea of today.

First is a small channel with iron red, steaming and largely oxygen-free water – filled from below with bubbling liquid above 160 degrees F. This was Earth as it would have existed, in a general way, as oxygen was becoming more prevalent on our planet some 2.4 billion years ago. Microbes exist, but life is spare at best.

Right next to this ancient scene is region of green-red water filled with cyanobacteria – the single-cell creatures that helped bring masses of oxygen into our atmosphere and oceans.  Locals come to this natural “onsen” for traditional hot baths, but they have to make their way carefully because the rocky floor is slippery with green mats of the bacteria.

And then there is the Philippine Sea, cool but with spurts of warm water shooting up from below into the cove.

All of this within a area of maybe 100 square feet.

It is a unique hydrothermal scene, and one recently studied by two researchers from the Earth-Life Science Institute in Tokyo – evolutionary microbiologist Shawn McGlynn and ancient virus specialist Tomohiro Mochizuki.

They were taking measurements of temperature, salinity and more, as well as samples of the hot gas and of microbial life in the iron-red water. Cyanobacterial mats are collected in the greener water, along with other visible microbe worlds.

Shawn McGlynn, associate professor at the Earth Life Science Institute in Tokyo scoops some iron-rich water from a channel on Shikine-jima Island, 100 miles from Tokyo. (Nerissa Escanlar)

The scientific goals are to answer specific questions – are the bubbles the results of biology or of geochemical processes? What are the isotopic signatures of the gases? What microbes and viruses live in the super-hot sections? And can cyanobacteria and iron co-exist?

All are connected, though, within the broad scientific effort underway to ever more specifically understand conditions on Earth through the eons, and how those conditions can help answer fundamental questions of how life might have begun.

“We really don’t know what microbiology looked like 2.5 billion or 1.5 billion years ago,” said McGlynn, “But this is a place we can go where we can try to find out.… Read more

Could High-Energy Radiation Have Played an Important Role in Getting Earth Ready For Life?

A version of this article first appeared in Astrobiology Magazine, www.astrobio.net.

The fossil remains of a natural nuclear reactor in Oklo, Gabon.  It entered a fission state some 2 billion years ago, and so would not have been involved in any origin of life scenario.  But is a proof of concept that these natural reactors have existed and some were widespread on earth Earth.  It is but one possible source of high energy particles on early Earth. The yellow rock is uranium oxide. (Robert D. Loss, Curtin University, Australia)

Life on early Earth seems to have begun with a paradox: while life needs water as a solvent, the essential chemical backbones of early life-forming molecules fall apart in water. Our universal solvent, it turns out, can be extremely corrosive.

Some have pointed to this paradox as a sign that life, or the precursor of life, originated elsewhere and was delivered here via comets or meteorites. Others have looked for solvents that could have the necessary qualities of water without that bond-breaking corrosiveness.

In recent years the solvent often put forward as the eligible alternative to water is formamide, a clear and moderately irritating liquid consisting of hydrogen, carbon, nitrogen and oxygen. Unlike water, it does not break down the long-chain molecules needed to form the nucleic acids and proteins that make up life’s key initial instruction manual, RNA. Meanwhile it also converts via other useful reactions into key compounds needed to make nucleic acids in the first place.

Although formamide is common in star-forming regions of space, scientists have struggled to find pathways for it to be prevalent, or even locally concentrated, on early Earth. In fact, it is hardly present on Earth today except as a synthetic chemical for companies.

New research presented by Zachary Adam, an earth scientist at Harvard University, and Masashi Aono, a complex systems scientist at Earth-Life Science Institute (ELSI) at Tokyo Institute of Technology, has produced formamide by way of a surprising and reproducible pathway: bombardment with radioactive particles.

 

In a room fitted for cobalt-60 testing on the campus of the Tokyo Institute of Technology, a team of researchers gather around the (still covered) cobalt-60 and vials of the chemicals they were testing. The ELSI scientists are (from left) Masashi Aono,  James Cleaves, Zachary Adam and Riquin Yi.  (Isao Yoda)

The two and their colleagues exposed a mixture of two chemicals known to have existed on early Earth (hydrogen cyanide and aqueous acetonitrile) to the high-energy particles emitted from a cylinder of cobalt-60, an artificially produced radioactive isotope commonly used in cancer therapy.… Read more

Messy Chemistry: A New Way to Approach the Origins of Life

Astrobiologist and chemist Irena Mamajanov and prebiotic chemist Kuhan Chandru in their messy chemistry garb at the Earth-Life Science Institute (ELSI) in Tokyo. Mamajanov leads an effort at the institute to study a new “messy” path to understanding how some prebiotic chemical systems led to building blocks of life on early Earth. (Nerissa Escanlar)

More than a half century ago, Stanley Miller and Harold Urey famously put water and gases believed to make up the atmosphere of early Earth into a flask with water, sparked the mix with an electric charge, and produced amino acids and other chemical building blocks of life.

The experiment was hailed as a ground-breaking reproduction of how the essential components of life may have been formed, or at least a proof of concept that important building blocks of life could be formed from more simple components.

Little discussed by anyone outside the origins of life scientific community was that the experiment also produced a lot of a dark, sticky substance, a gooey tar that covered the beaker’s insides. It was dismissed as largely unimportant and regrettable then, and in the thousands of parallel origins of life experiments that followed.

Today, however, some intrepid researchers are looking at the tarry residue in a different light.

Tarry residue from an experiment — a common result when organic compounds are heated.

Just maybe, they argue, the tar was equally if not more important as those prized amino acids (which, after all, were hidden away in the tar until they were extracted out.) Maybe the messy tar – produced by the interaction of organic compounds and an energy source — offers a pathway forward in a field that has produced many advances but ultimately no breakthrough.

Those now studying the tar call their research “messy chemistry,” as opposed to the “clean” chemistry that focused on the acclaimed organic compounds.

There are other centers where different versions of “messy chemistry” research are under way — including George Cody’s lab at the Carnegie Institution for Sciences and Nicholas Hud’s at the Georgia Institute of Technology — but it is probably most concentrated at the Earth-Life Science Institute in Tokyo (ELSI.)

There, messy chemistry is viewed as an ignored but promising way forward, and almost a call to arms.

“In classical origin-of-life synthetic chemistry and biology you’re looking at one reaction and analyzing its maximum result. It’s A+B = C+D,” said Irena Mamajanov, an astrobiologist with a background in chemistry who is now a principal investigator ELSI and head of the overall messy chemistry project.… Read more

Certain Big, Charged Molecules Are Universal to Life on Earth. Can They Help Detect It In The Far Solar System?

 

This article of mine, slightly tweaked for Many Worlds, first appeared today (July 6)  in Astrobiology Magazine,  www.astrobio.net

NASA’s Cassini spacecraft completed its deepest-ever dive through the icy plume of Enceladus on Oct. 28, 2015. The spacecraft did not have instruments that could detect life, but missions competing for NASA New Frontiers funding will — raising the thorny question of how life might be detected. (NASA/JPL-Caltech)

As NASA inches closer to launching new missions to the Solar System’s outer moons in search of life, scientists are renewing their focus on developing a set of universal characteristics of life that can be measured.

There is much debate about what might be considered a clear sign of life, in part, because there are so many definitions separating the animate from the inanimate.

NASA’s prospective missions to promising spots on Europa, Enceladus and Titan have their individual approaches to detecting life, but one respected voice in the field says there is a better way that’s far less prone to false positives.

Noted chemist and astrobiologist Steven Benner says life’s signature is not necessarily found in the presence of particular elements and compounds, nor in its effects on the surrounding environment, and is certainly not something visible to the naked eye (or even a sophisticated camera).

Rather, life can be viewed as a structure, a molecular backbone that Benner and his group, Foundation for Applied Molecular Evolution (FfAME), have identified as the common inheritance of all living things. Its central function is to enable what origin-of-life scientists generally see as an essential dynamic in the onset of life and its increased complexity and spread: Darwinian evolution via transfer of information, mutation and the transfer of those mutations.

“What we’re looking for is a universal molecular bio-signature, and it does exist in water,” says Benner. “You want a genetic molecule that can change physical conditions without changing physical properties — like DNA and RNA can do.”

Steven Benner, director of the Foundation for Applied Molecular Evolution or FfAME. (SETI)

Looking for DNA or RNA on an icy moon, or elsewhere would presuppose life like our own — and life that has already done quite a bit of evolving.

A more general approach is to find a linear polymer (a large molecule, or macromolecule, composed of many repeated subunits, of which DNA and RNA are types) with an electrical charge. That, he said, is a structure that is universal to life, and it can be detected.… Read more

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