Category: Early Earth (page 2 of 3)

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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To Understand Habitability, We Need to Return to Venus

This image shows the night side of Venus in thermal infrared. It is a false-color image using data from the Japanese spacecraft Akatsuki’s IR2 camera in two wavelengths, 1.74 and 2.26 microns. Darker regions denote thicker clouds, but changes in color can also denote differences in cloud particle size or composition from place to place.  JAXA / ISAS / DARTS / Damia Bouic

“You can feel what it’s like on Venus here on Earth,” said Kevin McGouldrick from the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder. “Heat a hot plate until it glows red, place your palm on its surface and then run over that hand with a truck.”

The surface of Venus is a hellish place. Suffocated by a thick atmosphere, pressure on the Venusian surface is 92 times greater than on the surface of Earth. Temperatures sit at a staggering 863°F (462°C), which is sufficient to melt lead.

The longest a spacecraft has survived in these conditions is a mere 127 minutes; a record set by the Russian Venera 13 mission over 35 years ago.

As the brightest planet in the night sky, Venus allured ancient astronomers into naming the world after the Roman mythological goddess of love and beauty. This now seems an ironic choice, but the contrast between distant observation and surface conditions produces an apt juxtaposition for exoplanets.

The comparison has led to an article in Nature Geoscience by McGouldrick and a nine author white paper advising on astrobiology strategy for the National Science Foundation. The conclusion of both publications echoes the irony of Venus’s name: we need to return to the inferno of Venus to understand habitable worlds.

A portion of western Eistla Regio is displayed in this three-dimensional perspective view of the surface of Venus. Synthetic aperture radar data from the spacecraft Magellan is combined with radar altimetry to develop a three-dimensional map of the surface. Rays cast in a computer intersect the surface to create a three-dimensional perspective view.  The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image, a frame from a video released in 1991, was produced at NASA’s JPL Multimission Image Processing Laboratory.

In the last 25 years, scientists have discovered over 3,500 extrasolar planets. The vast majority of these worlds have not been imaged directly, but are detected by tiny influences on their host star.… Read more

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… 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,

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

In Search of Panspermia (and Life on Icy Moons)


Sometimes personal affairs intervene for all of us, and they have now for your Many Worlds writer and his elderly father.  But rather than remain off the radar screen, I wanted to repost this column which has a new import. 

It turns out that versions of the instrument described below — a miniature gene sequencing device produced by Oxford Nanopore — have been put forward as the kind of technology that could detect life in the plume of Enceladus, or perhaps on Europa or Titan. 

Major figures in the astrobiology field, including Steve Benner of the Foundation for Applied Molecular Evolution (FfAME) and Chris McKay of NASA Ames Research Center see this kind of detection of the basic polymer backbone of RNA or DNA life as a potentially significant way forward.  Three different “Icy Moon” teams are vying for a NASA New Frontiers mission to Enceladus and Titan, and this kind of technology plays a role in at least one of the proposed missions.


Early Earth, like early Mars and no doubt many other planets, was bombarded by meteorites and comets. Could they have arrived "living" microbes inside them?

Early Earth, like early Mars and no doubt many other planets, was bombarded by meteorites and comets. Could they have arrived “living” microbes inside them?

When scientists approach the question of how life began on Earth, or elsewhere, their efforts generally involve attempts to understand how non-biological molecules bonded, became increasingly complex, and eventually reached the point where they could replicate or could use sources of energy to make things happen.  Ultimately, of course, life needed both.

Researchers have been working for some time to understand this very long and winding process, and some have sought to make synthetic life out of selected components and energy.  Some startling progress has been made in both of these endeavors, but many unexplained mysteries remain at the heart of the processes.  And nobody is expecting the origin of life on Earth (or elsewhere) to be fully understood anytime soon.

To further complicate the picture, the history of early Earth is one of extreme heat caused by meteorite bombardment and, most important, the enormous impact some 4.5 billion years of the Mars-sized planet that became our moon.  As a result, many early Earth researchers think the planet was uninhabitable until about 4 billion years ago.

Yet some argue that signs of Earth life 3.8 billion years ago have been detected in the rock record, and lifeforms were certainly present 3.5 billion years ago.  Considering the painfully slow pace of early evolution — the planet, after all, supported only single-cell life for several billion years before multicellular life emerged — some

dna animation. the big 300

A DNA helix animation.

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Nobel Laureate Jack Szostak: Exoplanets Gave The Origin of Life Field a Huge Boost

Jack Szostak, Nobel laureate and pioneering researcher in the origin-of-life field, was the featured speaker at a workshop this week at the Earth-Life Science Institute (ELSI) in Tokyo.  One goal of his Harvard lab is to answer this once seemingly impossible question:  was the origin of life on Earth essentially straight-forward and “easy,” or was it enormously “hard” and consequently rare in the universe. (Nerissa Escanlar)

Sometimes tectonic shifts in scientific disciplines occur because of discoveries and advances in the field.  But sometimes they occur for reasons entirely outside the field itself.  Such appears to be case with origins-of-life studies.

Nobel laureate Jack Szostak was recently in Tokyo to participate in a workshop at the Earth-Life Science Institute (ELSI) at the Tokyo Institute of Technology on “Reconstructing the Phenomenon of Life To Retrace the Emergence of Life.”

The talks were technical and often cutting-edge, but the backstory that Szostak tells of why he and so many other top scientists are now in the origins of life field was especially intriguing and illuminating in terms of how science progresses.

Those ground-shifting discoveries did not involve traditional origin-of-life questions of chemical transformations and pathways.  They involved exoplanets.

“Because of the discovery of all those exoplanets, astronomy has been transformed along with many other fields,” Szostak said after the workshop.

“We now know there’s a large range of planetary environments out there, and that has stimulated a huge amount of interest in where else in the universe might there be life.  Is it just here?  We know for sure that lots of environments could support life and we also would like to know:  do they?

“This has stimulated much more laboratory-based work to try to address the origins question.  What’s really important is for us to know whether the transition from chemistry to biology is easy and can happen frequently and anywhere, or are there one or many difficult steps that make life potentially very rare?”

In other words, the explosion in exoplanet science has led directly to an invigorated scientific effort to better understand that road from a pre-biotic Earth to a biological Earth — with chemistry that allows compounds to replicate, to change, to surround themselves in cell walls, and to grow ever more complex.

With today’s increased pace of research, Szostak said, the chances of finding some solid answers have been growing.  In fact, he’s quite optimistic that an answer will ultimately be forthcoming to the question of how life began on Earth.… Read more

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