Red Dwarf Stars and the Planets Around Them

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Artist rendering of a red dwarf or M star, with three exoplanets orbiting. About 75 percent of all stars in the sky are the cooler, smaller red dwarfs. (NASA)

It’s tempting to look for habitable planets around red dwarf stars, which put out far less luminosity and so are less blinding.  But is it wise?

That question has been near the top of the list for many exoplanet scientists, especially those involved in the search for habitable worlds.

Red dwarfs are plentiful (about three-quarters of all the stars out there) and the planets orbiting them are easier to observe because the stars are so small compared to our Sun and so an Earth-sized planet blocks a greater fraction of starlight.  Because planets orbiting red dwarfs are much closer in to their host stars, the observing geometry favors detecting more transits.

A potentially rich target, but with some drawbacks that have become better understood in recent years.  Not only are most planets orbiting these red dwarf stars tidally locked, with one side always facing the sun and the other in darkness, but the life history of red dwarfs is problematic.  They start out with powerful flares that many scientists say would sterilize the close-in planets forever.

Also, they are theorized to be prone to losing whatever water remains even if the stellar flares don’t do it. Originally, it was thought that this would happen because of a “runaway greenhouse,” where a warming planet under a brightening star would evaporate enough water from its oceans to create a thick blanket of H2O vapor at high altitudes and block the escape of radiation, leading to further warming and the eventual loss of all the planet’s water.

The parching CO2 greenhouse of a planet like Venus may be the result of that.  Later it was realized that on many planets, another mechanism called the “moist greenhouse” might create a similar thick blanket of water vapor at high altitudes long before a planet ever got to the runaway greenhouse stage.

Finally now has come some better news about red dwarf exoplanets.  Using 3-D models that characterize atmospheres going back, forward and to the sides, researchers found atmospheric conditions quite different from those predicted by 1-D models that capture changes only going from the surface straight up.

One paper found that using some pretty simple observations and calculations, scientists could determine the bottom line likelihood of whether or not the planet would be undone by a moist greenhouse effect.  The other found that these red dwarf exoplanets could have atmospheres that are always heavily clouded, but could still have surface temperatures that are moderate.

The new studies also enlarge the size of the habitable zones in which exoplanets could be orbiting a red dwarf or other “cool” star, making more of them potentially habitable.

The green sections are the habitable zones surround the different star types.  The term refers to the region around a star where water on a planet could remain liquid at least part of the time.  The term does not mean the planets in the zone are necessarily habitable, but that they make it past one particular large hurdle.  (NASA)

 

“This is good news for those of us hoping to find habitable planets,” said Anthony Del Genio, a senior research scientist at NASA’s Goddard Institute for Space Studies (GISS) in New York, and co-author of a new paper in The Astrophysical Journal.

“These studies show that a broader range of planets could have stable climates than we thought.  This is a broadening of the width of the habitable zone by showing that we can get closer to a star and still have a potentially habitable planet.”

Yuka Fujii, author of the Astrophysical Journal article, specializes in exoplanet characterization, planetary atmospheres, planet formation, and origin of life issues. (Nerissa Escanlar)

In a NASA release, the paper’s lead author, Yuka Fujii, said this: “Using a model that more realistically simulates atmospheric conditions, we discovered a new process that controls the habitability of exoplanets and will guide us in identifying candidates for further study.” Fujii was formerly at NASA GISS and now is a project associate professor  at the Earth-Life Science Institute in Tokyo.

Since telescope time available for exoplanets will be quite limited on observatories such as the James Webb Space Telescope — which has many astronomical tasks to accomplish — the Earth-sized exoplanets around red dwarfs seem to be the more technologically feasible target to observe.

Scientists have to observe Earth-size planets for a long time and for many transits in front of the star to get a good enough signal to interpret. So given that, it will be impossible to observe all, or even many, of the candidate Earth-size planets discovered so far or will be discovered.  Tough choices have to be made.

What the group found using their 3-D models is that unlike the predictions from 1-D models, this moist greenhouse effect does not set in immediately for a particular luminosity of the star. Rather, it occurs more gradually as the star becomes brighter.

That fact, Del Genio said, makes the findings from the new 3-D modeling studies additionally important because they can help observers determine which small, rocky exoplanets might be most promising in terms of habitability.

They do this by identifying — and then eliminating — exoplanets that have undergone what is called a “moist greenhouse” transformation.

Anthony Del Genio, leader of the GISS team using cutting edge Earth climate models to better understand conditions on exoplanets.

A moist greenhouse occurs when a watery exoplanet orbits too close to its host star. Light from the star will then heat the oceans until they begin to evaporate and are lost to space.

This happens when water vapor rises to a layer in the upper atmosphere called the stratosphere and gets broken into its elemental components (hydrogen and oxygen) by ultraviolet light from the star.
The extremely light hydrogen atoms can then escape to space. Planets in the process of losing their oceans this way are said to have entered a “moist greenhouse” state because of their humid stratospheres.

What the group found using their 3-D models is that unlike the runaway greenhouse effect this moist greenhouse effect does not set it immediately at a particular temperature threshold.  Rather, it occurs more gradually, even over eons.

They came to this conclusion because the upper atmosphere heating turned out to be a function of the infrared radiation coming from the stars rather than from turbulent convective activity (as in massive thunderstorms) from the surface, as earlier believed.

The infrared radiation (which is at wavelengths slightly longer than the visible wavelength area of the spectrum) will warm the planet and cause what water is present to eventually. evaporate.

 

This is a plot of what the sea ice distribution could look like on a tidally locked ocean world. The star would be off to the right, blue is where there is open ocean, and white is where there is sea ice.  (NASA/GISS/Anthony Del Genio)

This paper comes on the heels of a related one in the August edition of  The Astrophysical Journal.

Ravi Kopparapu, a research scientist at NASA Goddard and Eric Wolf of the University of Colorado, Boulder came to a similar conclusion about surfaces on exoplanets orbiting red dwarfs. As they wrote in their abstract, the modeling  “implies that some planets around low mass (red dwarf) stars can simultaneously undergo water-loss and remain habitable.”

They also reported general circulation model 3-D modeling that showed moist greenhouse scenarios around red dwarfs were slow moving and took place at relatively low temperatures. As a result, oceans could remain for a long time — even billions of years — as they slowly evaporated.

Both groups use general circulation models (GCM), though different ones.  GCMs are an advanced type of climate model that looks at the general circulation patterns of planetary atmospheres and oceans.  They were initially designed to model Earth’s climate patterns, but now are used for exoplanets as well.

The original theory of the moist greenhouse scenario was put forward in the 1980s by James Kasting of Pennsylvania State University, who also did much original work on the concept of a habitable zone and helped popularize the concept.  Both the runaway greenhouse and the moist greenhouse have become important factors in exoplanet study.

 

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

2.5 Billion Years of Earth History in 100 Square Feet

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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. It’s a remarkable site for going back in time.”

In particular, there are not many natural environments with high levels of dissolved iron like this site. Yet scientists know from the rock record that there were periods of Earth history when the oceans were similarly filled with iron.

Mochizuki elaborated: “We’re trying to figure out what was possible chemically and biologically under certain conditions long ago.

“If you have something happening now at this unusual place – with the oxygen and iron mixing in the hot water to turn the water red – then there’s a chance that what we find today was there as well billions of years ago. ”

Tomohiro Mochizuki at collecting samples directly from the spot where 160 degree F water pushes up through the rock at Jinata hot spring. (Nerissa Escanlar)

The Jinata hot springs, as the area is known, is on Shikine-jima Island, one of the furthest out in the Izu chain of islands that starts in Tokyo Bay. More than 100 miles from Tokyo itself, Shikine-jima is nonetheless part of Tokyo Prefecture.

The Izu islands are all volcanic, created by the underwater movements of the Philippine and Pacific tectonic plates. That boundary remains in flux, and thus the hot springs and volcanoes. The terrain can be pretty rugged: in English, Jinata translates to something like Earth Hatchet, since the hot spring is at the end of a path through what does look like a rock rising that had been cut through with a hatchet.

Hot springs and underwater thermal vents have loomed large in thinking about origins of life since it became known in recent decades that both generally support abundant life – microbial and larger – and supply nutrients and even energy in the form of electricity from vents and electron transfers from chemical reactions.

And so not surprisingly, vents are visited and sampled not infrequently by ELSI scientists. McGlynn was on another hydrothermal vent field trip in Iceland over the summer with, among others, ELSI Origins Network fellow Donato Gionovelli and ELSI principal investigator and electrochemist Ruyhei Nakamura..

McGlynn’s work is focused on how electrons flow between elements and compounds, a transfer that he sees as a basic architecture for all life. With so many compelling flows occurring in such a small space, Jinata is a superb laboratory.

The volcanic Izu island chain, starting in Tokyo Bay and going out into the Philippine Sea.

For Mochizuki, the site turned out to be exciting but definitely not a goldmine. That’s because his speciality is viruses that live at very high temperatures, and even the bubbling hot spring in the iron trench measured about 73 degrees C (163 degrees F.) The viruses he incubates live at temperatures between closer to 90 C (194 F), not far from the boiling point.

His goal in studying these high-temperature (hyperthermophilic) viruses is to look back to the earliest days of life forming on Earth, using viruses as his navigators. Since life is thought by many scientists to have begun in a super hot RNA world, Mochizuki wants to look at viruses still living in those conditions today to see what they can tell us.

So far, he explained, what they have told us is that the RNA in the earliest lifeforms on Earth – denizens of the Archaean kingdom – did not have viruses. And this is puzzling.

So Mochizuki is always interested in going to sample hot springs and thermal vents to collect high temperature viruses, and to look for surprises.

Though the bubbling waters were so hot that both researchers had difficulty standing in the water with boots on and holding their collection vials with gloves, it was not hot enough for what Mochizuki is after. But that certainly didn’t stop him from taking as many samples as he could, including some for other ELSI researchers doing different work but still needing interesting samples.

Researchers often need to be inventive on field trips, and that was certainly the case at Jinata. When McGlynn first tried to sample the bubbles at the scalding spring, his hands and feet quickly felt on fire and he had to retreat.

To speed the process, he and Mochizuki built a funnel out of a large plastic water bottle, a device that allowed the bubbles to be collected and directed into the sample vial without the gloved hands being so close to the heat.   The booted feet, however, remained a problem and the heat just had to be endured.

Nearby the steaming bubbling of the hot spring were collections of what appeared to be fine etchings on the bottom of the red channel. These faint designs, McGlynn explained, were the product of a microbe that makes it’s way along the bottom and deposits lines of processed iron oxide as it goes. So while the elegant designs are not organic, the creatures that creates them surely is.

“Touch the area and the lines go poof,” McGlynn said. “That’s because they’re just the iron oxide; nothing more. Next to us is the water with much less iron and a lot more oxygen, and so there are blooms of (green) cyanobacteria. Touch them and they don’t go poof, they stick to your hand because they’re alive.”

Filaments created by microbes as they deposit iron oxide at the bottom of small channel. (Marc Kaufman)

McGlynn also collects some of the the poofs to get at the microbes making the unusual etchings. It may be a microbe never identified before.

As a microbiologist, he is of course interested in identifying and classifying microbes. He initially thought the microbes in the iron channel would be anaerobic, but he found that even tiny amount of oxygen making their way into the springs from the atmosphere made most aerobic, or possibly anaerobes capable of surviving with oxygen (which usually is toxic to them.)

He also found that laboratory studies that found cyanobacteria would not flourish in the presence of iron were not accurate in nature, or certainly were not accurate at Jinata onsen.

But it is that flow of electrons that really drives McGlynn – he even dreams of them at night, he told me.

One of the goals of his work, and that of his colleague and sometimes collaborator at ELSI, geobiochemist Yuichiro Ueno, is to answer some of the outstanding questions about that flow of electrons (electricity) from the core of the Earth. The energy transits through the mantle, to the surface and then often is in contact with the biosphere (all living things) before it enters the atmosphere and sometimes disappears into space.

He likened the process to the workings of a gigantic battery, with the iron core as the cathode and the oxygen in the atmosphere as the anode. Understanding the chemical pathways traveled by the electrons today, he is convinced, will tell a great deal about conditions on the early Earth as well.

It’s all important research in what is a chipping away of the many unknowns in the stories of the origins of Earth and the origin of life.

A boundary between where the very hot iron-rich water meets and the less hot water with thriving cyanobacteria colonies at Jinata.

The field work also illustrated the hit-and-miss nature of these kind of outings. While McGlynn has not come up with Jinata surprises or novel understandings, he was so taken with the setting that he wondered if a seemly empty building not too far from the site could be turned into an ELSI marine lab.

And while Mochizuki did not find sufficiently hot water for his work, he might still be coming back to the island, or others nearby. That’s because he learned of a potentially much hotter spring at a spot where the sea hits one of the island’s steep cliffs – a site that requires boat access that was unsafe in the choppy waters during this particular visit.

In addition, McGlynn and Mochizuki did make some surprising discoveries, though they didn’t involve microbes, electron transfer or viruses.

During a morning visit to a different hot spring, they came across a team of what turned out to be officials of the Izu islands – all dressed in suits and ties. They were visiting Shikine-jima as part of a series of joint islands visit to assess economic development opportunities.

The officials were intrigued to learn what the scientists were up to, and made some suggestions of other spots to sample. One was an island occupied by Japanese self-defense forces and generally closed to outsiders. But the island is known to have areas of extremely hot water just below the surface of the land, sometimes up to 100 C (212 F.)

The officials gave their cards and told the scientists to contact them if they wanted to get onto that island for sampling. And as for the official from Shikine-jima, he was already thinking big.

“It would be a very good thing,” he said, “if you found the origin of life on our island.

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

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

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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. The result, they report, was the production of substantial amounts of formamide more quickly than earlier attempts by researchers using theoretical models and in laboratory settings.

It remains unclear whether early Earth had enough radioactive material in the right places to produce the chemical reactions that led to the formation of formamide. And even if the conditions were right, scientists cannot yet conclude that formamide played an important role in the origin of life.

Still, the new research furthers the evidence of the possible role of alternative solvents and presents a differing picture of the basis of life. Furthermore, it is suggestive of processes that might be at work on other exoplanets as well – where solvents other than water could, with energy supplied by radioactive sources, provide the necessary setting for simple compounds to be transformed into far more complex building blocks.

Formamide is a clear liquid which is miscible with water and has an ammonia-like odor.

“Imagine that water-based life was preceded by completely unique networks of interacting molecules that approximated, but were distinct from and followed different chemical rules, than life as we know it,” said Adam.

Their work was presented at recent gatherings of the International Society for the Study of the Origin of Life, and the Astrobiology Science Conference.

The team of Adam and Aono are hardly the first to put forward the formamide hypothesis as a solution to the water paradox, and they are also not the first to posit a role for high-energy, radioactive particles in the origin of life.

An Italian team led by Rafaelle Saladino of Tuscia University recently proposed formamide as a chemical that would supply necessary elements for life and would avoid the ‘water paradox.’ Since the time that Marie Curie described the phenomenon of radioactivity, scientists have proposed innumerable ways that the emission of particle-shedding atomic nuclei might have played roles, either large or small, in initiating life on Earth.

Merging the science of formamide and radioactivity, as Adam and Aono have done, is a potentially significant step forward, though one that needs deeper study.

“If we have formamide as a solvent, those precursor molecules can be kept stable, a kind of cradle to preserve very interesting products,” said Aono, who has moved to Tokyo-based Keio University while remaining a fellow at ELSI.

Aono and technician Isao Yoda in the radiation room with the cobalt-60 safely tucked away. (Nerissa Escanlar.)

The experiment with cobalt-60 did not begin as a search for a way to concentrate the production of formamide. Rather, Adam was looking more generally into the effects of gamma rays on a variety of molecules and solvents, while Aono was exploring radioactive sources for a role in the origin of life.

The two came together somewhat serendipitously at ELSI, an origins-of-life research center created by the Japanese government. ELSI was designed to be a place for scientists from around the world and from many different disciplines to tackle some of the notoriously difficult issues in origins of life research. At ELSI, Adam, who had been unable to secure sites to conduct laboratory tests in the United States, learned from Aono about a sparingly-used (and free) cobalt-60 lab; they promptly began collaborating.

It is well known that the early Earth was bombarded by high-energy cosmic particles and gamma rays. So is the fact that numerous elements (aluminum-26, iron-60, iodine-129) have existed as radioactive isotopes that can emit radiation for minutes to millennium, and that these isotopes were more common on early Earth than today. Indeed, the three listed above are now extinct on Earth, or nearly extinct, in their natural forms

Less known is the presence of “natural nuclear reactors” as sites where a high concentration of uranium in the presence of water has led to self-sustaining nuclear fission. Only one such spot has been found —in the Oklo region of the African nation of Gabon — where spent radioactive material was identified at 16 sites separate sites. Scientists ultimately concluded widespread natural nuclear reactions occurred in the region some 2 billion years ago.

That time frame would mean that the site would have been active well after life had begun on Earth, but it is a potential proof of concept of what could have existed elsewhere long before

Adam and Aono remain agnostic about where the formamide-producing radioactive particles came from. But they are convinced that it is entirely possible that such reactions took place and helped produce an environment where each of the backbone precursors of RNA could readily be found in close quarters.

Current scientific thinking about how formamide appeared on Earth focuses on limited arrival via asteroid impacts or through the concentration of the chemical in evaporated water-formamide mixtures in desert-like conditions. Adam acknowledges that the prevailing scientific consensus points to low amounts of formamide on early Earth.

“We are not trying to argue to the contrary,” he said, “but we are trying to say that it may not matter.”

If you have a unique place (or places) on the Earth creating significant amounts of formamide over a long period of time through radiolysis, then an opportunity exists for the onset of some unique chemistry that can support the production of essential precursor compounds for life, Adam said.

“So, the argument then shifts to— how likely was it that this unique place existed? We only need one special location on the entire planet to meet these circumstances,” he said.

Zachary Adam, an earth scientist in the lab of Andrew Knoll at Harvard University. (Nerissa Escanlar)

After that, the system set into motion would have the ability to bring together the chemical building blocks of life.

“That’s the possibility that we look forward to investigating in the coming years,” Adam said.

James Cleaves, an organic chemist also at ELSI and a co-author of the cobalt-60 paper, said while production of formamide from much simpler compounds represents progress, “there are no silver bullets in origin of life work. We collect facts like these, and then see where they lead.”

Another member of the cobalt-60 team is Albert Fahrenbach, a former postdoc in the lab of Harvard University’s Nobel laureate Jack Szostak and now an associate principal investigator at ELSI.

An organic chemist, Fahrenbach was a late-comer to the project, brought in because Cleaves thought the project could use his expertise.

“Connecting the origins of life, or precursors chemicals, with radiolysis (or radioactivty) was an active field back in the 70s and 80s,” he said. “Then it pretty much died out and went out of fashion.”

Fahrenbach said he remains uncertain about any possible role for radiolysis in the origin of life story. But the experiment did intrigue him greatly, it led him to experiment with some of the chemicals formed by the gamma ray blasts, and he says the results have been productive.

“Without this experiment, I would definitely not be going down some very interesting paths,” he said

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

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

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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.

“But life is not like that; it isn’t any single reaction. They’re looking at a subset of reactions and we ask: ‘Why not look at the whole complex system?’”

 

Irena Mamajanov of ELSI, with colleague Yuki Suna, synthesizes particular complex molecules similar to enzymes to explore the many pathways that could have been involved in the production of actual early enzymes. The term “messy chemistry” grew out of a prebiotic chemistry conference at the Carnegie Institution for Science in Washington several years ago.  (Nerissa Escanlar)

There’s a scientific lineage here – researchers have worked with complex systems and reaction systems in many fields, and in principle this is the same. It’s taking a “systems” approach and applying it to that black box period on Earth when non- biological chemicals were slowly transformed (or transformed themselves) into chemical systems with the attributes of “life.”

The messy chemistry work is getting noticed, and Mamajanov was a featured speaker on the “New Approaches to the Origins of Life” plenary at the 2017 Astrobiology Science Conference, in Mesa, Arizona. At ELSI alone, researchers have been working on messy chemistry using metals, using electricity, using radioactivity, using computational chemistry and using analytical chemistry to tease out patterns and structure in the tars.

Mamajanov says this messy chemistry approach – which she learned to some extent as a fellow at both Carnegie and Georgia Tech — makes intuitive, as well as scientific sense because life is nothing if not complex.

Wouldn’t it be logical for the origin of life to be found in some of the earliest complex systems on Earth, rather than in looking for straight-line processes that progress almost independent of all the chemistry happening around them?

It stands to reason that the gunky tar played a role, she said, because tars allow some essential processes to occur. Tars can concentrate compounds, can encapsulate them, and can provide a kind of primitive (messy) scaffolding that could eventually evolve into the essential backbones of a living entity.

 

Stanley Miller and the iconic Miller-Urey experiment in 1952. The experiment added some of the chemicals thought to be in the Early Earth atmosphere, some water, and an electric charge. The result was the creation of some building blocks of life (amino acids, nucleotides) and lots of what was long considered a problematic residue of tar.

It’s the structure, in fact, that stands out as a particularly promising aspect of messy chemistry. More traditional synthetic biology is looking for simple molecular structures created by clean reactions, while messy chemistry is doing the opposite.

The goal of messy chemists is to see what interesting chemical processes take place within a defined portion of the messy, complex sample. What unexpected, surprising compounds or chemical structures might be formed? And how might they shed light on the process of chemical self-organization and more generally the origin of life question?

In her lab on the basement floor of the ELSI main building, Mamajanov works with colleagues to synthesize her messy molecules and push further into understanding their structures, their potential ability to adapt, and their suitability as possible precursors to the RNA and DNA molecules that characterize life.

Her specific area of study is hyperbranched polymers – three-dimensional, tree-shaped chains of repeating molecules that connect with other similar molecules. The result is globular, presents multitudes of chemical reactions and has some hidden and protected spaces inside their globs.  Related synthetic, or bio-mimicked chemicals (i.e., modeled on biological compounds and processes) have been used by the drug industry for some time.

With these hyperbranched polymers, Mamajanov has worked to produce pathways within the messy systems where the polymers show characteristics of evolvability.

Hyperbranch polymers exist in nature, most prominently in the process that petroleum oil is form, but are also made synthetically for research.  The tar that Mamajamov makes out of the chemicals is greasy but clear rather than brownish.

Her hyperbranched polymers are synthetic, as are those of noted synthetic chemists–in-search-of-biology such as Steven Benner, at the Foundation for Applied Molecular Evolution and Gerald Joyce of the Scripps Institute.

But the starting points are quite different, as are the goals. The two men are working to create clean chemical systems that produce the building block molecules that they want, but without the tar.  Mamajamov is intentionally making tar.

Eric Smith, a specialist in complexity systems, physics and chemistry who is also at ELSI sees the messy approach as containing the seeds of an important new way forward. “What is now called messy chemistry used to be completely out of the mainstream,” he said. “That is no longer the case.”

Smith described how John Sutherland of the Laboratory of Molecular Biology at Cambridge, U.K. won accolades for his work on the prebiotic assembly of important building blocks for RNA, using controlled chemistry that avoided all the messiness.

But he was also criticized later for using a such a controlled model – early Earth, after all, did not have any outside controller – and Smith said Sutherland is incorporating the messier side of prebiotic chemistry today, although tar remains an enemy rather than a potential friend.

“Now he’s going back to a one pot synthesis, allowing reactions that would have to be less controlled than what he was doing before,” Smith said of Sutherland. “He may do it in a way quite different from Irena and others involved in messy chemistry, but it seems to allow for many more complex reactions.”

Eric Smith is a senior scientist at ELSI steeped in the world of complex systems. (Nerissa Escanlar)

And complexity is indeed the desired endpoint. Not simply repetitive reactions and not random ones, but rather reactions that are very complex but ultimately structured.

This is where another novel aspect of the messy chemistry approach comes into play: Mamajanov and others at ELSI are collaborating with practitioners of “artificial chemistry,” computer simulated versions of what could be happening in messy interactions.

The work is being done primarily by Nathaniel Virgo, an artificial life specialist who uses computing to learn about how chemical systems behave once you leave the laboratory world where the number of chemical components is small and controlled.

And his big question: “Are there situations in which you can get ‘order from disorder’ in chemistry – to start with a messy system and have it spontaneously become more ordered? If so, what kinds of conditions are required for this to happen, and what kinds of ordered states can result?

Mamajanov needs Virgo’s computations to analyze and project forward what a messy chemical system might do, since the sheer number of possible chemical reactions involved is huge. And Virgo needs the messy chemistry as a test bed of sorts for his abstracted questions about, in effect, making order out of what appears to be chaos. They are, for each other, hypothesis-generating machines.

Virgo pointed to several primary reasons why computational work is important for answering the question of creating order from disorder (and ultimately, he is convinced, life from non-life.)

“The first is simply that studying messy chemistry experimentally is really hard. If you have a test tube containing a mess, it takes a lot of work to find out what molecules are in it, and basically impossible to know what reactions are happening, at least not without an enormous amount of work. In contrast, in a simulation you know exactly what molecules and reactions are present, even if there are millions of different types.”

Nathaniel Virgo, a specialist in computational artificial-life, speaks during an ELSI seminar in Tokyo.  (Nerissa Escanlar)

The second reason involves the fundamental issue of studying specific chemical systems versus studying general mechanisms.

“As a complex systems scientist, I first want to know what, in general, is required, for a given phenomenon to occur. Once this is known, it should become clear which real systems will exhibit the right kinds of properties.

“This allows us to narrow down the vast space of possible hypotheses for the origins of life, rather than simply testing them one at a time. It should also give us some insight into the question of whether life might be possible with completely different kinds of chemistry than the protein-nucleic acid-metabolite chemistry we have on Earth.

From his studies he has found that in messy chemical systems, chemical self-production occurs and tht the systems can change dramatically in response to small changes such as an increased temperature.

“This suggests that messy chemistry is fundamentally qualitatively different from clean chemistry – adding more species doesn’t just mean the system gets harder to study, it also means that fundamentally new things can happen.”

And in the origins of life world, things are happening.

 

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Cassini Nearing the End, Still Working Hard

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Spiral density wave on Saturn’s moon Janus. (NASA/JPL-Caltech)

As the Cassini mission embarks on its final dive this Friday into Saturn, it will continue taking photos all the way down (or as far as it remains operations.)

We’ve grown accustomed to seeing remarkable images for the mission and the planet, but clearly the show is not over, and perhaps far from it.

This is what NASA wrote describing the image above:

This view  shows a wave structure in Saturn’s rings known as the Janus 2:1 spiral density wave. Resulting from the same process that creates spiral galaxies, spiral density waves in Saturn’s rings are much more tightly wound. In this case, every second wave crest is actually the same spiral arm which has encircled the entire planet multiple times.

This is the only major density wave visible in Saturn’s B ring. Most of the B ring is characterized by structures that dominate the areas where density waves might otherwise occur, but this innermost portion of the B ring is different.

For reasons researchers do not entirely understand, damping of waves by larger ring structures is very weak at this location, so this wave is seen ringing for hundreds of bright wave crests, unlike density waves in Saturn’s A ring.

The image gives the illusion that the ring plane is tilted away from the camera toward upper-left, but this is not the case. Because of the mechanics of how this kind of wave propagates, the wavelength decreases with distance from the resonance. Thus, the upper-left of the image is just as close to the camera as the lower-right, while the wavelength of the density wave is simply shorter.

This wave is remarkable because Janus, the moon that generates it, is in a strange orbital configuration. Janus and Epimetheus (see PIA12602) share practically the same orbit and trade places every four years. Every time one of those orbit swaps takes place, the ring at this location responds, spawning a new crest in the wave.

The distance between any pair of crests corresponds to four years’ worth of the wave propagating downstream from the resonance, which means the wave seen here encodes many decades’ worth of the orbital history of Janus and Epimetheus.

According to this interpretation, the part of the wave at the very upper-left of this image corresponds to the positions of Janus and Epimetheus around the time of the Voyager flybys in 1980 and 1981, which is the time at which Janus and Epimetheus were first proven to be two distinct objects (they were first observed in 1966).

Epimetheus also generates waves at this location, but they are swamped by the waves from Janus, since Janus is the larger of the two moons.

 

The clouds covering the planet itself consist of ammonia ice.  Further down is also some water ice, some ammonium hydrosulfide ice, and further still is ammonia in a gas phase. Some cloud layers are more than 1000 miles thick. (NASA/JPL-Caltech.

This image is from a few months ago, but it certainly puts you there above the deep, deep clouds of Saturn.  False color was used to make the patterns more discernible.

Saturn has some remarkable features in its atmosphere. When the Voyager missions traveled to the planet in the early 1980s, it imaged a hexagon-shaped cloud formation near the north pole. Twenty-five years later, infrared images taken by Cassini revealed the storm was still spinning, powered by jet streams that push it to speeds of about 220 mph (100 meters per second). At 15,000 miles  across, the long-lasting storm could easily contain an Earth or two.

Cassini is now on its last full orbit, to be following by its partial finale.  The final 22 orbits leading to the plunge into the clouds looked like this:

Cassini’s final orbits, in blue, have taken the spacecraft closer to the planet than ever before, and into the space between the rings and the top of the cloud layers. (NASA/JPL-Caltech)

 

And here is a Jet Propulsion Lab video recapping the Cassini mission and describing its Friday rendezvous:

 

(NASA/JPL-Caltech)

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.