Record-breaking recovery of rocks that originated in Earth's mantle could reveal secrets of planet's history

Scientists have recovered the first long section of rocks that originated in the Earth's mantle, the layer below the crust and the planet's largest component.

The rocks will help unravel the mantle's role in the origins of life on Earth, the volcanic activity generated when it melts, and how it drives the global cycles of important elements such as carbon and hydrogen, according to the team.

The nearly continuous 1,268 metres of mantle rock was recovered from a "tectonic window," a section of the seabed where rocks from the mantle were exposed along the Mid-Atlantic Ridge, during Expedition 399 "Building Blocks of Life, Atlantis Massif" of the ocean drilling vessel JOIDES Resolution in Spring 2023.

With attempts dating back to the early 1960s, the recovery was a record-breaking achievement led by the International Ocean Discovery Program, an international marine research consortium of more than 20 countries that retrieves cores -- cylindrical samples of sediment and rock -- from the ocean floor to study Earth's history.

Since then, the expedition team has been compiling an inventory of the recovered mantle rocks to understand their composition, structure and context.

Their findings, presented in the journal Science, reveal a more extensive history of melting in the recovered rocks than expected.

Lead author Professor Johan Lissenberg from Cardiff University's School of Earth and Environmental Sciences, said: "When we recovered the rocks last year, it was a major achievement in the history of the Earth sciences, but, more than that, its value is in what the cores of mantle rocks could tell us about the makeup and evolution of our planet.

"Our study begins to look at the composition of the mantle by documenting the mineralogy of the recovered rocks, as well as their chemical makeup.

"Our results differ from what we expected. There is a lot less of the mineral pyroxene in the rocks, and the rocks have got very high concentrations of magnesium, both of which results from much higher amounts of melting than what we would have predicted."

This melting occurred as the mantle rose from the deeper parts of the Earth towards the surface.

Results from further analysis of this process could have major implications for the understanding of how magma is formed and leads to volcanism, the researchers claim.

"We also found channels through which melt was transported through the mantle, and so we are able to track the fate of magma after it is formed and travels upwards to the Earth's surface.

"This is important because it tells us how the mantle melts and feeds volcanoes, particularly those on the ocean floor that account for the majority of volcanism on Earth. Having access to these mantle rocks will allow us to make the connection between the volcanoes and the ultimate source of their magmas."

The study also provides initial results on how olivine, an abundant mineral in mantle rocks, reacts with seawater, leading to a series of chemical reactions that produce hydrogen and other molecules that can fuel life.

Scientists believe this might have been one of the underpinning processes in the origin of life on Earth.

Dr Susan Q Lang, an associate scientist in Geology and Geophysics at the Woods Hole Oceanographic Institution, who was a co-chief scientist on the expedition and part of a team continuing to analyse rock and fluid samples, said: "The rocks that were present on early Earth bear a closer resemblance to those we retrieved during this expedition than the more common rocks that make up our continents today.

"Analysing them gives us a critical view into the chemical and physical environments that would have been present early in Earth's history, and that could have provided a consistent source of fuel and favorable conditions over geologically long timeframes to have hosted the earliest forms of life."

The international team of more than 30 scientists from the JOIDES Resolution expedition will continue their research on the recovered drill cores to address a wide range of problems.

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A recipe for zero-emissions fuel: Soda cans, seawater, and caffeine

A sustainable source for clean energy may lie in old soda cans and seawater.

MIT engineers have found that when the aluminum in soda cans is exposed in its pure form and mixed with seawater, the solution bubbles up and naturally produces hydrogen -- a gas that can be subsequently used to power an engine or fuel cell without generating carbon emissions. What's more, this simple reaction can be sped up by adding a common stimulant: caffeine.

In a study appearing today in the journal Cell Reports Physical Science, the researchers show they can produce hydrogen gas by dropping pretreated, pebble-sized aluminum pellets into a beaker of filtered seawater. The aluminum is pretreated with a rare-metal alloy that effectively scrubs aluminum into a pure form that can react with seawater to generate hydrogen. The salt ions in the seawater can in turn attract and recover the alloy, which can be reused to generate more hydrogen, in a sustainable cycle.

The team found that this reaction between aluminum and seawater successfully produces hydrogen gas, though slowly. On a lark, they tossed into the mix some coffee grounds and found, to their surprise, that the reaction picked up its pace.

In the end, the team discovered that a low concentration of imidazole -- an active ingredient in caffeine -- is enough to significantly speed up the reaction, producing the same amount of hydrogen in just five minutes, compared to two hours without the added stimulant.

The researchers are developing a small reactor that could run on a marine vessel or underwater vehicle. The vessel would hold a supply of aluminum pellets (recycled from old soda cans and other aluminum products), along with a small amount of gallium-indium and caffeine. These ingredients could be periodically funneled into the reactor, along with some of the surrounding seawater, to produce hydrogen on demand. The hydrogen could then fuel an onboard engine to drive a motor or generate electricity to power the ship.

"This is very interesting for maritime applications like boats or underwater vehicles because you wouldn't have to carry around seawater -- it's readily available," says study lead author Aly Kombargi, a PhD student in MIT's Department of Mechanical Engineering. "We also don't have to carry a tank of hydrogen. Instead, we would transport aluminum as the 'fuel,' and just add water to produce the hydrogen that we need."

The study's co-authors include Enoch Ellis, an undergraduate in chemical engineering; Peter Godart PhD '21, who has founded a company to recycle aluminum as a source of hydrogen fuel; and Douglas Hart, MIT professor of mechanical engineering.

Shields up

The MIT team, led by Hart, is developing efficient and sustainable methods to produce hydrogen gas, which is seen as a "green" energy source that could power engines and fuel cells without generating climate-warming emissions.

One drawback to fueling vehicles with hydrogen is that some designs would require the gas to be carried onboard like traditional gasoline in a tank -- a risky setup, given hydrogen's volatile potential. Hart and his team have instead looked for ways to power vehicles with hydrogen without having to constantly transport the gas itself.

They found a possible workaround in aluminum -- a naturally abundant and stable material that, when in contact with water, undergoes a straightforward chemical reaction that generates hydrogen and heat.

The reaction, however, comes with a sort of Catch-22: While aluminum can generate hydrogen when it mixes with water, it can only do so in a pure, exposed state. The instant aluminum meets with oxygen, such as in air, the surface immediately forms a thin, shield-like layer of oxide that prevents further reactions. This barrier is the reason hydrogen doesn't immediately bubble up when you drop a soda can in water.

In previous work, using fresh water, the team found they could pierce aluminum's shield and keep the reaction with water going by pretreating the aluminum with a small amount of rare metal alloy made from a specific concentration of gallium and indium. The alloy serves as an "activator," scrubbing away any oxide buildup and creating a pure aluminum surface that is free to react with water. When they ran the reaction in fresh, de-ionized water, they found that one pretreated pellet of aluminum produced 400 milliliters of hydrogen in just five minutes. They estimate that just 1 gram of pellets would generate 1.3 liters of hydrogen in the same amount of time.

But to further scale up the system would require a significant supply of gallium indium, which is relatively expensive and rare.

"For this idea to be cost-effective and sustainable, we had to work on recovering this alloy postreaction," Kombargi says.

By the sea

In the team's new work, they found they could retrieve and reuse gallium indium using a solution of ions. The ions -- atoms or molecules with an electrical charge -- protect the metal alloy from reacting with water and help it to precipitate into a form that can be scooped out and reused.

"Lucky for us, seawater is an ionic solution that is very cheap and available," says Kombargi, who tested the idea with seawater from a nearby beach. "I literally went to Revere Beach with a friend and we grabbed our bottles and filled them, and then I just filtered out algae and sand, added aluminum to it, and it worked with the same consistent results."

He found that hydrogen indeed bubbled up when he added aluminum to a beaker of filtered seawater. And he was able to scoop out the gallium indium afterward. But the reaction happened much more slowly than it did in fresh water. It turns out that the ions in seawater act to shield gallium indium, such that it can coalesce and be recovered after the reaction. But the ions have a similar effect on aluminum, building up a barrier that slows its reaction with water.

As they looked for ways to speed up the reaction in seawater, the researchers tried out various and unconventional ingredients.

"We were just playing around with things in the kitchen, and found that when we added coffee grounds into seawater and dropped aluminum pellets in, the reaction was quite fast compared to just seawater," Kombargi says.

To see what might explain the speedup, the team reached out to colleagues in MIT's chemistry department, who suggested they try imidazole -- an active ingredient in caffeine, which happens to have a molecular structure that can pierce through aluminum (allowing the material to continue reacting with water), while leaving gallium indium's ionic shield intact.

"That was our big win," Kombargi says. "We had everything we wanted: recovering the gallium indium, plus the fast and efficient reaction."

The researchers believe they have the essential ingredients to run a sustainable hydrogen reactor. They plan to test it first in marine and underwater vehicles. They've calculated that such a reactor, holding about 40 pounds of aluminum pellets, could power a small underwater glider for about 30 days by pumping in surrounding seawater and generating hydrogen to power a motor.

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Nanoscale movies shed light on one barrier to a clean energy future

Left unchecked, corrosion can rust out cars and pipes, take down buildings and bridges, and eat away at our monuments.

Corrosion can also damage devices that could be key to a clean energy future. And now, Duke University researchers have captured extreme close-ups of that process in action.

"By studying how and why renewable energy devices break down over time, we might be able to extend their lifetime," said chemistry professor and senior author Ivan Moreno-Hernandez.

In his lab at Duke sits a miniature version of one such device. Called an electrolyzer, it separates hydrogen out of water, using electricity to power the reaction.

When the electricity to power electrolysis comes from renewable sources such as wind or solar, the hydrogen gas it churns out is considered a promising source of clean fuel, because it takes no fossil fuels to produce and it burns without creating any planet-warming carbon dioxide.

A number of countries have plans to scale up their production of so-called "green hydrogen" to help curb their dependence on fossil fuels, particularly in industries like steel- and cement-making.

But before hydrogen can go mainstream, some big obstacles need to be overcome.

Part of the trouble is electrolyzers require rare metal catalysts to function, and these are prone to corrosion. They're not the same after a year of operation than they were in the beginning.

In a study published April 10 in the Journal of the American Chemical Society, Moreno-Hernandez and his Ph.D. student Avery Vigil used a technique called liquid phase transmission electron microscopy to study the complex chemical reactions that go on between these catalysts and their environment that cause them to decay.

You might remember from high school that to make hydrogen gas, an electrolyzer splits water into its constituent hydrogen and oxygen molecules. For the current study, the team focused on a catalyst called ruthenium dioxide that speeds up the oxygen half of the reaction, since that's the bottleneck in the process.

"We essentially put these materials through a stress test," Vigil said.

They zapped nanocrystals of ruthenium dioxide with high-energy radiation, and then watched the changes wrought by the acidic environment inside the cell.

To take pictures of such tiny objects, they used a transmission electron microscope, which shoots a beam of electrons through nanocrystals suspended inside a super-thin pocket of liquid to create time-lapse images of the chemistry taking place at 10 frames per second.

The result: desktop-worthy close-ups of virus-sized crystals, more than a thousand times finer than a human hair, as they get oxidized and dissolve into the acidic liquid around them.

"We're actually able to see the process of this catalyst breaking down with nanoscale resolution," Moreno-Hernandez said.

Over the course of five minutes, the crystals broke down fast enough to "render a real device useless in a matter of hours," Vigil said.

Zooming in hundreds of thousands of times, the videos reveal subtle defects in the crystals' 3D shapes that create areas of strain, causing some to break down faster than others.

By minimizing such imperfections, the researchers say it could one day be possible to design renewable energy devices that last two to three times longer than they currently do.

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Juno spacecraft measures oxygen production on Jupiter's moon, Europa

NASA's Juno spacecraft has directly measured charged oxygen and hydrogen molecules from the atmosphere of one of Jupiter's largest moons, Europa. According to a new study co-authored by SwRI scientists and led by Princeton University, these observations provide key constraints on the potential oxygenation of its subsurface ocean.

"These findings have direct implications on the potential habitability of Europa," said Juno Principal Investigator Dr. Scott Bolton of SwRI, a co-author of the study.

"This study provides the first direct in-situ measurement of water components existing in Europa's atmosphere, giving us a narrow range that could support habitability."

In 2022, Juno completed a flyby of Europa, coming as close as 352 kilometers to the moon.

The SwRI-developed Jovian Auroral Distributions Experiment (JADE) instrument aboard Juno detected significant amounts of charged molecular oxygen and hydrogen lost from the atmosphere.

"For the first time, we've been able to definitively detect hydrogen and oxygen with in-situ measurements and further confirm that Europa's atmosphere is made primarily of hydrogen and oxygen molecules," said SwRI Staff Scientist and co-author Dr. Robert Ebert.

The source of these molecules is thought to be water ice on Europa's surface.

Jupiter's rampant radiation breaks H2O's molecular bonds, leaving behind oxygen and hydrogen.

The heavier oxygen molecules remain more constrained to the surface, or near-surface atmosphere, while the lighter-weight hydrogen predominately escapes into the atmosphere and beyond.

Oxygen produced in the ice is either lost from the atmosphere and/or sequestered in the surface.

Oxygen retained in Europa's ice may work its way to its subsurface ocean as a possible source of metabolic energy.

"Europa's ice shell absorbs radiation, protecting the ocean underneath. This absorption also produces oxygen within the ice, so in a way, the ice shell acts as Europa's lung, providing a potential oxygen source for the ocean." said Princeton University Research Scholar Dr. Jamey Szalay, the study's lead author.

"We put narrow constraints on the total oxygen production at Europa currently at around 12 kg per second. Before Juno, previous estimates ranged from a few kg per second to over 1,000 kg per second. The findings unambiguously demonstrate oxygen is continuously produced in the surface, just a good bit lower than we expected."

"We designed JADE to measure the charged particles that create Jupiter's auroras," said SwRI Staff Scientist and co-author Dr. Frederic Allegrini.

"Flybys of Europa were not part of the primary Juno mission. JADE was designed to work in a high-radiation environment but not necessarily Europa's environment, which is constantly bombarded with high levels of radiation. Nonetheless, the instrument performed beautifully."

The new measurements contribute to a greater understanding of Europa and its environment, open the door for newer, more precise models.

The study's new estimation of how much oxygen is produced within Europa's surface, for instance, could inform future research related to its subsurface ocean and potential habitability.

As these observations provide the first charged particle composition measurements within Europa's vicinity, they provide an important new window into the moons' complex interaction with its environment.

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Bright galaxies put dark matter to the test

For the past year and a half, the James Webb Space Telescope has delivered astonishing images of distant galaxies formed not long after the Big Bang, giving scientists their first glimpses of the infant universe. Now, a group of astrophysicists has upped the ante: Find the tiniest, brightest galaxies near the beginning of time itself, or scientists will have to totally rethink their theories about dark matter.

The team, led by UCLA astrophysicists, ran simulations that track the formation of small galaxies after the Big Bang and included, for the first time, previously neglected interactions between gas and dark matter. They found that the galaxies created are very tiny, much brighter, and form more quickly than they do in typical simulations that don''t take these interactions into account, instead revealing much fainter galaxies.

Small galaxies, also called dwarf galaxies, are present throughout the universe, and are often thought to represent the earliest type of galaxy. Small galaxies are thus especially interesting to scientists studying the origins of the universe. But the small galaxies they find don't always match what they think they should find. Those closest to the Milky Way spin quicker or are not as dense as in simulations, indicating that the models might have omitted something, such as these gas-dark matter interactions.

The new research, published in The Astrophysical Journal Letters, improves the simulations by adding dark matter interactions with gas and finds that these faint galaxies may have been much brighter than expected early in the universe's history, when they were just beginning to form. The authors suggest scientists should try to find small galaxies that are much brighter than expected using telescopes like the Webb telescope. If they only find faint ones, then some of their ideas about dark matter might be wrong.

Dark matter is a type of hypothetical matter that does not interact with electromagnetism or light. Thus, it is impossible to observe using optics, electricity or magnetism. But dark matter does interact with gravity, and its presence has been inferred from the gravitational effects it has on ordinary matter -- the stuff that makes up all the observable universe. Even though 84% of the matter in the universe is thought to be made of dark matter, it has never been detected directly.

All galaxies are surrounded by a vast halo of dark matter, and scientists think that dark matter was essential to their formation. The "standard cosmological model" astrophysicists use to understand galaxy formation describes how clumps of dark matter in the very early universe drew in ordinary matter through gravity, causing the formation of stars and creating the galaxies we see today. Because most dark matter particles -- called cold dark matter -- are thought to move much slower than the speed of light, this process of accumulation would have occurred gradually.

But over 13 billion years ago, prior to the formation of the first galaxies, ordinary matter, consisting of hydrogen and helium gas from the Big Bang, and dark matter were moving relative to one another. The gas streamed at supersonic velocities past dense thickets of more slowly moving dark matter that should have pulled it in to form galaxies.

"Indeed, in models that do not take streaming into account, this is exactly what happens," said Claire Williams, a UCLA doctoral student and the paper's first author. "Gas is attracted to the gravitational pull of dark matter, forms clumps and knots so dense that hydrogen fusion can occur, and thus forms stars like our sun."

But Williams and co-authors on the Supersonic Project team, a group of astrophysicists from the United States, Italy and Japan led by UCLA physics and astronomy professor Smadar Naoz, found if they added the streaming effect of different velocities between dark and ordinary matter to the simulations, the gas landed far away from the dark matter and was prevented from forming stars right away. When the accumulated gas fell back into the galaxy millions of years later, a massive burst of star formation occurred all at once. Because these galaxies had many more young, hot, luminous stars than ordinary small galaxies for a time, they shone much brighter.

"While the streaming suppressed star formation in the smallest galaxies, it also boosted star formation in dwarf galaxies, causing them to outshine the non-streaming patches of the universe," Williams said. "We predict that the Webb telescope will be able to find regions of the universe where galaxies will be brighter, heightened by this velocity. The fact that they should be so bright might make it easier for the telescope to discover these small galaxies, which are typically extremely hard to detect only 375 million years after the Big Bang."

Because dark matter is impossible to study directly, searching for bright patches of galaxies in the early universe could offer an effective test for theories about dark matter, which has been fruitless so far.

"The discovery of patches of small, bright galaxies in the early universe would confirm that we are on the right track with the cold dark matter model because only the velocity between two kinds of matter can produce the type of galaxy we're looking for," said Naoz, the Howard and Astrid Preston Professor of Astrophysics. "If dark matter does not behave like standard cold dark matter and the streaming effect isn't present, then these bright dwarf galaxies won't be found and we need to go back to the drawing board."

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Study uncovers potential origins of life in ancient hot springs

Newcastle University research turns to ancient hot springs to explore the origins of life on Earth.

The research team, funded by the UK's Natural Environmental Research Council, investigated how the emergence of the first living systems from inert geological materials happened on the Earth, more than 3.5 billion years ago.

Scientists at Newcastle University found that by mixing hydrogen, bicarbonate, and iron-rich magnetite under conditions mimicking relatively mild hydrothermal vent results in the formation of a spectrum of organic molecules, most notably including fatty acids stretching up to 18 carbon atoms in length.

Published in the journal Communications Earth & Environment, their findings potentially reveal how some key molecules needed to produce life are made from inorganic chemicals, which is essential to understanding a key step in how life formed on the Earth billions of years ago.

Their results may provide a plausible genesis of the organic molecules that form ancient cell membranes, that were perhaps selectively chosen by early biochemical processes on primordial Earth.

Fatty acids in the early stages of life

Fatty acids are long organic molecules that have regions that both attract and repel water that will automatically form cell-like compartments in water naturally and it is these types of molecules that could have made the first cell membranes.

Yet, despite their importance, it was uncertain where these fatty acids came from in the early stages of life.

One idea is that they might have formed in the hydrothermal vents where hot water, mixed with hydrogen-rich fluids coming from underwater vents mixed with seawater containing CO2.

The group replicated crucial aspects of the chemical environment found in early Earth's oceans and the mixing of the hot alkaline water from around certain types of hydrothermal vents in their laboratory.

They found that when hot hydrogen-rich fluids were mixed with carbon dioxide-rich water in the presence of iron-based minerals that were present on the early Earth it created the types of molecules needed to form primitive cell membranes.

Lead author, Dr Graham Purvis, conducted the study at Newcastle University and is currently a Postdoctoral Research Associate at Durham University.

He said: "Central to life's inception are cellular compartments, crucial for isolating internal chemistry from the external environment. These compartments were instrumental in fostering life-sustaining reactions by concentrating chemicals and facilitating energy production, potentially serving as the cornerstone of life's earliest moments.

The results suggest that the convergence of hydrogen-rich fluids from alkaline hydrothermal vents with bicarbonate-rich waters on iron-based minerals could have precipitated the rudimentary membranes of early cells at the very beginning of life.

This process might have engendered a diversity of membrane types, some potentially serving as life's cradle when life first started.

Principal Investigator Dr Jon Telling, Reader in Biogeochemistry, at School of Natural Environmental Sciences, added:

"We think that this research may provide the first step in how life originated on our planet. Research in our laboratory now continues on determining the second key step; how these organic molecules which are initially 'stuck' to the mineral surfaces can lift off to form spherical membrane-bounded cell-like compartments; the first potential 'protocells' that went on to form the first cellular life."

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Astronomers discover first population of binary stripped stars

Astronomers at the University of Toronto have discovered a population of massive stars that have been stripped of their hydrogen envelopes by their companions in binary systems. The findings, published today in Science, shed light on the hot helium stars that are believed to be the origins of hydrogen-poor core-collapse supernovae and neutron star mergers.

For over a decade, scientists have theorized that approximately one in three massive stars are stripped of their hydrogen envelope in binary systems. Yet, until now, only one possible candidate had been identified.

"This was such a big, glaring hole," says co-lead author Maria Drout, an Assistant Professor in the David A. Dunlap Department of Astronomy & Astrophysics and a Dunlap Institute for Astronomy & Astrophysics Associate at the University of Toronto.

"If it turned out that these stars are rare, then our whole theoretical framework for all these different phenomena is wrong, with implications for supernovae, gravitational waves, and the light from distant galaxies," Drout says. "This finding shows these stars really do exist."

"Going forward, we are going to be able to do much more detailed physics with these stars," Drout says. "For example, predictions for how many neutron star mergers we should see are dependent on the properties of these stars, such as how much material comes off of them in stellar winds. Now, for the first time, we'll be able to measure that, whereas people have been extrapolating it before."

Binary stripped stars have been previously evoked to explain why a third of core-collapse supernovae contain much less hydrogen than a typical explosion of a Red Supergiant star. Drout and her colleagues propose that these newly discovered stars will eventually explode as hydrogen-poor supernovae. These star systems are also thought to be necessary to form neutron star mergers, like those that emit gravitational waves detected from Earth by the LIGO experiment.

In fact, the researchers believe that a few objects in their current sample are stripped stars with neutron star or blackhole companions. These objects are at the stage immediately before they become double neutron star or neutron star plus blackhole systems that could eventually merge.

"Many stars are part of a cosmic dance with a partner, orbiting each other in a binary system. They're not solitary giants but part of dynamic duos, interacting and influencing each other throughout their lifetimes," says Bethany Ludwig, a PhD student in in the David A. Dunlap Department of Astronomy & Astrophysics at the University Toronto and the third author on this paper. "Our work sheds light on these fascinating relationships, revealing a universe that is far more interconnected and active than we previously imagined."

"Just as humans are social beings, stars too, especially the massive ones, are rarely alone," Ludwig says.

As stars evolve and expand to become red giants, the hydrogen at the outer edges of one can be stripped by the gravitational pull of its companion -- leaving a very hot helium core exposed. The process can take tens of thousands, or even hundreds of thousands, of years.

Stripped stars are difficult to find because much of the light they emit is outside of the visible light spectrum and can be obstructed by dust in the universe or outshone by their companion stars.

Drout and her collaborators began their search in 2016. Having studied hydrogen-poor supernovae during her PhD, Drout set out to find the stripped stars thought to be at the heart of them during a NASA Hubble Postdoctoral Fellowship at the Observatories of the Carnegie Institution for Science. She met fellow co-author Ylva Götberg, now Assistant Professor at the Institute of Science and Technology Austria (ISTA), at a conference, who had recently built new theoretical models of what these stars should look like.

Drout, Götberg, and their collaborators designed a new survey to look in the ultraviolet part of the spectrum where extremely hot stars emit most of their light. While invisible to the naked eye, ultraviolet light can be detected by specialized instruments and telescopes.

Using data from the Swift Ultra-Violet/Optical Telescope, the researchers collected brightnesses for millions of stars in the Large and Small Magellanic Clouds, two of the closest galaxies to Earth. Ludwig developed the first wide-field UV catalog of the Magellanic Clouds and used UV photometry to detect systems with unusual UV emissions, signaling the possible presence of a stripped star.

They carried out a pilot study of 25 objects, obtaining optical spectroscopy with the Magellan Telescopes at Las Campanas Observatory between 2018 and 2022. They used these observations to demonstrate that the stars were hot, small, hydrogen-poor, and in binary systems -- all consistent with their model predictions.

Currently, the researchers are continuing to study the stars identified in this paper and expanding their search to find more. They will be looking both within nearby galaxies and within our own Milky Way with approved programs on the Hubble Space Telescope, the Chandra X-Ray Telescope, the Magellan Telescopes, and the Anglo-Australian Telescope. As part of this publication, all theoretical models and data used to identify these stars have been made public and available to other scientists.

Read more at Science Daily

Reaching for the (invisible) stars

Supernovae-stellar explosions as bright as an entire galaxy-have fascinated us since time immemorial. Yet, there are more hydrogen-poor supernovae than astrophysicists can explain. Now, a new Assistant Professor at the Institute of Science and Technology Austria (ISTA) has played a pivotal role in identifying the missing precursor star population. The results, now published in Science, go back to a conversation the involved professors had many years ago as junior scientists.

Some stars do not simply die down, but explode in a stellar blast that could outshine entire galaxies. These cosmic phenomena, called supernovae, spread light, elements, energy, and radiation in space and send galactic shock waves that could compress gas clouds and generate new stars. In other words, supernovae shape our universe. Among these, hydrogen-poor supernovae from exploding massive stars have long puzzled astrophysicists. The reason: scientists have not been able to put their finger on their precursor stars. It is almost as if these supernovae appeared out of nowhere.

"There are many more hydrogen-poor supernovae than our current models can explain. Either we can't detect the stars that mature on this path, or we must revise all our models," says ISTA Assistant Professor Ylva Götberg. She pioneered this work together with Maria Drout, an Associated Faculty Member of the Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Canada. "Single stars would typically explode as hydrogen-rich supernovae. Being hydrogen-poor indicates that the precursor star must have lost its thick hydrogen-rich envelope. This happens naturally in a third of all massive stars through envelope stripping by a binary companion star," says Götberg. Now, Götberg and Drout combined their areas of expertise in theoretical modeling and observation to hunt down the missing stars. Their quest is successful: they document a first-of-its-kind star population that finally bridges a large knowledge gap and sheds light on the origin of hydrogen-poor supernovae.

Binary stars and envelope stripping

The stars that Götberg and Drout search for go in pairs: interlocked in a binary star system. Some binary systems are well-known to us Earthlings: these include the brightest star in our night sky, Sirius A, and its faint companion star Sirius B. The Sirius binary system is located only 8.6 light-years away from Earth-a stone's throw in cosmic terms. This explains Sirius A's observed brightness in our night sky.

Astrophysicists expect the missing stars to be initially formed from massive binary systems. In a binary system, the stars would orbit around one another until the more massive star's thick, hydrogen-rich envelope expands. Eventually, the expanding envelope experiences a stronger gravitational pull to the companion star than to its own core. This causes a transfer of mass to begin, which eventually leads the entire hydrogen-rich envelope to be stripped off, leaving the hot and compact helium core exposed-more than 10 times hotter than the Sun's surface. This is precisely the type of stars that Götberg and Drout are looking for. "Intermediate mass helium stars stripped through binary interaction are predicted to play important roles in astrophysics. Yet, they were not observed until now," says Götberg. In fact, there is an important mass gap between the known classes of helium stars: the more massive Wolf-Rayet (WR) stars have more than 10 times the Sun's mass, and the low-mass subdwarf stars could have around half the Sun's mass. However, models have predicted the precursors of hydrogen-poor supernovae to lie between 2 and 8 solar masses following stripping.

Not just a needle in the haystack

Before Götberg and Drout's study, only one star was found to fulfill the expected mass and composition criteria and was called "Quasi-WR" (or "Almost Wolf-Rayet"). "Yet, the stars that follow this path have such a long lifetime that many must be scattered all over the observable universe," says Götberg. Did the scientists simply not "see" them? Thus, Götberg and Drout drew on their complementary expertise. With the help of UV photometry and optical spectroscopy, they identified a population of 25 stars that are consistent with the expectations for intermediate-mass helium stars. The stars are located in two well-studied neighboring galaxies, the Large and the Small Magellanic Clouds. "We showed that these stars were bluer than the stellar birthline, the bluest phase in a single star's lifetime. Single stars mature by evolving towards the redder region of the spectrum. A star only shifts in the opposite direction if its outer layers are removed-something that is expected to be common in interacting binary stars and rare among single massive stars," explains Götberg.

The scientists then verified their candidate star population using optical spectroscopy: they showed that the stars had strong spectral signatures of ionized helium. "Strong ionized helium lines tell us two important things: first, they confirm that the stars' outermost layers are dominated by helium and, second, that their surface is very hot. This is what happens to stars left as an exposed, compact, helium-rich core following stripping," says Götberg. Yet, both stars in a binary system contribute to the observed spectra. Thus, this technique allowed the researchers to classify their candidate population depending on which star contributed the most to the spectrum. "This work allowed us to find the missing population of intermediate-mass, stripped helium stars, the predicted progenitors of hydrogen-poor supernovae. These stars have always been there and there are probably many more out there. We must simply come up with ways to find them," says Götberg. "Our work may be one of the first attempts, but there should be other ways possible."

From graduate students at a conference to group leaders

The idea behind this project sparked in a discussion following a talk by Götberg at a conference that she and Drout attended during their graduate studies. Both scientists, then Early Career Researchers reaching for the stars, are now group leaders in their field. Götberg joined ISTA in September following her research at the Carnegie Observatories in Pasadena, California, as a NASA Hubble postdoctoral fellow. At ISTA, Götberg joins the Institute's growing ranks of young group leaders in astrophysics and leads her own group focused on studying the binary interactions of stars.

Read more at Science Daily

Solar-powered device produces clean water and clean fuel at the same time

A floating, solar-powered device that can turn contaminated water or seawater into clean hydrogen fuel and purified water, anywhere in the world, has been developed by researchers.

The device, developed by researchers at the University of Cambridge, could be useful in resource-limited or off-grid environments, since it works with any open water source and does not require any outside power.

It takes its inspiration from photosynthesis, the process by which plants convert sunlight into food. However, unlike earlier versions of the 'artificial leaf', which could produce green hydrogen fuel from clean water sources, this new device operates from polluted or seawater sources and can produce clean drinking water at the same time.

Tests of the device showed it was able to produce clean water from highly polluted water, seawater, and even from the River Cam in central Cambridge. The results are reported in the journal Nature Water.

"Bringing together solar fuels production and water purification in a single device is tricky," said Dr Chanon Pornrungroj from Cambridge's Yusuf Hamied Department of Chemistry, the paper's co-lead author. "Solar-driven water splitting, where water molecules are broken down into hydrogen and oxygen, need to start with totally pure water because any contaminants can poison the catalyst or cause unwanted chemical side-reactions."

"In remote or developing regions, where clean water is relatively scarce and the infrastructure necessary for water purification is not readily available, water splitting is extremely difficult," said co-lead author Ariffin Mohamad Annuar. "A device that could work using contaminated water could solve two problems at once: it could split water to make clean fuel, and it could make clean drinking water."

Pornrungroj and Mohamad Annuar, who are both members of Professor Erwin Reisner's research group, came up with a design that did just that. They deposited a photocatalyst on a nanostructured carbon mesh that is a good absorber of both light and heat, generating the water vapour used by the photocatalyst to create hydrogen. The porous carbon mesh, treated to repel water, served both to help the photocatalyst float and to keep it away from the water below, so that contaminants do not interfere with its functionality.

In addition, the new device uses more of the Sun's energy. "The light-driven process for making solar fuels only uses a small portion of the solar spectrum -- there's a whole lot of the spectrum that goes unused," said Mohamad Annuar.

The team used a white, UV-absorbing layer on top of the floating device for hydrogen production via water splitting. The rest of the light in the solar spectrum is transmitted to the bottom of the device, which vaporises the water.

"This way, we're making better use of the light -- we get the vapour for hydrogen production, and the rest is water vapour," said Pornrungroj. "This way, we're truly mimicking a real leaf, since we've now been able to incorporate the process of transpiration."

A device that can make clean fuel and clean water at once using solar power alone could help address the energy and the water crises facing so many parts of the world. For example, the indoor air pollution caused by cooking with 'dirty' fuels, such as kerosene, is responsible for more than three million deaths annually, according to the World Health Organization. Cooking with green hydrogen instead could help reduce that number significantly. And 1.8 billion people worldwide still lack safe drinking water at home.

"It's such a simple design as well: in just a few steps, we can build a device that works well on water from a wide variety of sources," said Mohamad Annuar.

"It's so tolerant of pollutants, and the floating design allows the substrate to work in very cloudy or muddy water," said Pornrungroj. "It's a highly versatile system."

"Our device is still a proof of principle, but these are the sorts of solutions we will need if we're going to develop a truly circular economy and sustainable future," said Reisner, who led the research. "The climate crisis and issues around pollution and health are closely related, and developing an approach that could help address both would be a game-changer for so many people."

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Engineers develop an efficient process to make fuel from carbon dioxide

The search is on worldwide to find ways to extract carbon dioxide from the air or from power plant exhaust and then make it into something useful. One of the more promising ideas is to make it into a stable fuel that can replace fossil fuels in some applications. But most such conversion processes have had problems with low carbon efficiency, or they produce fuels that can be hard to handle, toxic, or flammable.

Now, researchers at MIT and Harvard University have developed an efficient process that can convert carbon dioxide into formate, a liquid or solid material that can be used like hydrogen or methanol to power a fuel cell and generate electricity. Potassium or sodium formate, already produced at industrial scales and commonly used as a de-icer for roads and sidewalks, is nontoxic, nonflammable, easy to store and transport, and can remain stable in ordinary steel tanks to be used months, or even years, after its production.

The new process, developed by MIT doctoral students Zhen Zhang, Zhichu Ren, and Alexander H. Quinn, Harvard University doctoral student Dawei Xi, and MIT Professor Ju Li, is described this week in the journal Cell Press Physical Sciences. The whole process -- including capture and electrochemical conversion of the gas to a solid formate powder, which is then used in a fuel cell to produce electricity -- was demonstrated at a small, laboratory scale. However, the researchers expect it to be scalable so that it could provide emissions-free heat and power to individual homes and even be used in industrial or grid-scale applications.

Other approaches to converting carbon dioxide into fuel, Li explains, usually involve a two-stage process: First the gas is chemically captured and turned into a solid form as calcium carbonate, then later that material is heated to drive off the carbon dioxide and convert it to a fuel feedstock such as carbon monoxide. That second step has very low efficiency, typically converting less than 20 percent of the gaseous carbon dioxide into the desired product, Li says.

By contrast, the new process achieves a conversion of well over 90 percent and eliminates the need for the inefficient heating step by first converting the carbon dioxide into an intermediate form, liquid metal bicarbonate. That liquid is then electrochemically converted into liquid potassium or sodium formate in an electrolyzer that uses low-carbon electricity, e.g. nuclear, wind, or solar power. The highly concentrated liquid potassium or sodium formate solution produced can then be dried, for example by solar evaporation, to produce a solid powder that is highly stable and can be stored in ordinary steel tanks for up to years or even decades, Li says.

Several steps of optimization developed by the team made all the difference in changing an inefficient chemical-conversion process into a practical solution, says Li, who holds joint appointments in the departments of Nuclear Science and Engineering and of Materials Science and Engineering.

The process of carbon capture and conversion involves first an alkaline solution based capture that concentrates carbon dioxide, either from concentrated streams such as from power plant emissions or from very low-concentration sources, even open air, into the form of a liquid metal-bicarbonate solution. Then, through the use of a cation-exchange membrane electrolyzer, this bicarbonate is electrochemically converted into solid formate crystals with a carbon efficiency of greater than 96 percent, as confirmed in the team's lab-scale experiments.

These crystals have an indefinite shelf life, remaining so stable that they could be stored for years, or even decades, with little or no loss. By comparison, even the best available practical hydrogen storage tanks allow the gas to leak out at a rate of about 1 percent per day, precluding any uses that would require year-long storage, Li says. Methanol, another widely explored alternative for converting carbon dioxide into a fuel usable in fuel cells, is a toxic substance that cannot easily be adapted to use in situations where leakage could pose a health hazard. Formate, on the other hand, is widely used and considered benign, according to national safety standards.

Several improvements account for the greatly improved efficiency of this process. First, a careful design of the membrane materials and their configuration overcomes a problem that previous attempts at such a system have encountered, where a buildup of certain chemical byproducts changes the pH, causing the system to steadily lose efficiency over time. "Traditionally, it is difficult to achieve long-term, stable, continuous conversion of the feedstocks," Zhang says. "The key to our system is to achieve a pH balance for steady-state conversion."

To achieve that, the researchers carried out thermodynamic modeling to design the new process so that it is chemically balanced and the pH remains at a steady state with no shift in acidity over time. It can therefore can continue operating efficiently over long periods. In their tests, the system ran for over 200 hours with no significant decrease in output. The whole process can be done at ambient temperatures and relatively low pressures (about five times atmospheric pressure).

Another issue was that unwanted side reactions produced other chemical products that were not useful, but the team figured out a way to prevent these side reactions by the introduction of an extra "buffer" layer of bicarbonate-enriched fiberglass wool that blocked these reactions.

The team also built a fuel cell specifically optimized for the use of this formate fuel to produce electricity. The stored formate particles are simply dissolved in water and pumped into the fuel cell as needed. Although the solid fuel is much heavier than pure hydrogen, when the weight and volume of the high-pressure gas tanks needed to store hydrogen is considered, the end result is an electricity output near parity for a given storage volume, Li says.

The formate fuel can potentially be adapted for anything from home-sized units to large scale industrial uses or grid-scale storage systems, the researchers say. Initial household applications might involve an electrolyzer unit about the size of a refrigerator to capture and convert the carbon dioxide into formate, which could be stored in an underground or rooftop tank. Then, when needed, the powdered solid would be mixed with water and fed into a fuel cell to provide power and heat. "This is for community or household demonstrations," Zhang says, "but we believe that also in the future it may be good for factories or the grid."

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Making hydrogen from waste plastic could pay for itself

Hydrogen is viewed as a promising alternative to fossil fuel, but the methods used to make it either generate too much carbon dioxide or are too expensive. Rice University researchers have found a way to harvest hydrogen from plastic waste using a low-emissions method that could more than pay for itself.

"In this work, we converted waste plastics -- including mixed waste plastics that don't have to be sorted by type or washed -- into high-yield hydrogen gas and high-value graphene," said Kevin Wyss, a Rice doctoral alumnus and lead author on a study published in Advanced Materials. "If the produced graphene is sold at only 5% of current market value -- a 95% off sale! -- clean hydrogen could be produced for free."

By comparison, 'green' hydrogen -- produced using renewable energy sources to split water into its two component elements -- costs roughly $5 for just over two pounds. Though cheaper, most of the nearly 100 million tons of hydrogen used globally in 2022 was derived from fossil fuels, its production generating roughly 12 tons of carbon dioxide per ton of hydrogen.

"The main form of hydrogen used today is 'gray' hydrogen, which is produced through steam-methane reforming, a method that generates a lot of carbon dioxide" said James Tour, Rice's T. T. and W. F. Chao Professor of Chemistry and a professor of materials science and nanoengineering. "Demand for hydrogen will likely skyrocket over the next few decades, so we can't keep making it the same way we have up until now if we're serious about reaching net zero emissions by 2050."

The researchers exposed plastic waste samples to rapid flash Joule heating for about four seconds, bringing their temperature up to 3100 degrees Kelvin. The process vaporizes the hydrogen present in plastics, leaving behind graphene -- an extremely light, durable material made up of a single layer of carbon atoms.

"When we first discovered flash Joule heating and applied it to upcycle waste plastic into graphene, we observed a lot of volatile gases being produced and shooting out of the reactor," Wyss said. "We wondered what they were, suspecting a mix of small hydrocarbons and hydrogen, but lacked the instrumentation to study their exact composition."

Using funding from the United States Army Corps of Engineers, the Tour lab acquired the necessary equipment to characterize the vaporized contents.

"We know that polyethylene, for example, is made of 86% carbon and 14% hydrogen, and we demonstrated that we are able to recover up to 68% of that atomic hydrogen as gas with a 94% purity," Wyss said. "Developing the methods and expertise to characterize and quantify all the gases, including hydrogen, produced by this method was a difficult but rewarding process for me.

"I am glad that techniques I learned and used in this work -- specifically life-cycle assessment and gas chromatography -- can be applied to other projects in our group. I hope that this work will allow for the production of clean hydrogen from waste plastics, possibly solving major environmental problems like plastic pollution and the greenhouse gas-intensive production of hydrogen by steam methane reforming."

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Water world? Methane, carbon dioxide in atmosphere of massive exoplanet

A new investigation with NASA's James Webb Space Telescope into K2-18 b, an exoplanet 8.6 times as massive as Earth, has revealed the presence of carbon-bearing molecules including methane and carbon dioxide. Webb's discovery adds to recent studies suggesting that K2-18 b could be a Hycean exoplanet, one which has the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface.

The first insight into the atmospheric properties of this habitable-zone exoplanet came from observations with NASA's Hubble Space Telescope, which prompted further studies that have since changed our understanding of the system.

K2-18 b orbits the cool dwarf star K2-18 in the habitable zone and lies 120 light-years from Earth in the constellation Leo. Exoplanets such as K2-18 b, which have sizes between those of Earth and Neptune, are unlike anything in our solar system. This lack of equivalent nearby planets means that these 'sub-Neptunes' are poorly understood, and the nature of their atmospheres is a matter of active debate among astronomers.

The suggestion that the sub-Neptune K2-18 b could be a Hycean exoplanet is intriguing, as some astronomers believe that these worlds are promising environments to search for evidence for life on exoplanets.

"Our findings underscore the importance of considering diverse habitable environments in the search for life elsewhere," explained Nikku Madhusudhan, an astronomer at the University of Cambridge and lead author of the paper announcing these results. "Traditionally, the search for life on exoplanets has focused primarily on smaller rocky planets, but the larger Hycean worlds are significantly more conducive to atmospheric observations."

The abundance of methane and carbon dioxide, and shortage of ammonia, support the hypothesis that there may be a water ocean underneath a hydrogen-rich atmosphere in K2-18 b. These initial Webb observations also provided a possible detection of a molecule called dimethyl sulfide (DMS). On Earth, this is only produced by life. The bulk of the DMS in Earth's atmosphere is emitted from phytoplankton in marine environments.

The inference of DMS is less robust and requires further validation. "Upcoming Webb observations should be able to confirm if DMS is indeed present in the atmosphere of K2-18 b at significant levels," explained Madhusudhan.

While K2-18 b lies in the habitable zone, and is now known to harbor carbon-bearing molecules, this does not necessarily mean that the planet can support life. The planet's large size -- with a radius 2.6 times the radius of Earth -- means that the planet's interior likely contains a large mantle of high-pressure ice, like Neptune, but with a thinner hydrogen-rich atmosphere and an ocean surface. Hycean worlds are predicted to have oceans of water. However, it is also possible that the ocean is too hot to be habitable or be liquid.

"Although this kind of planet does not exist in our solar system, sub-Neptunes are the most common type of planet known so far in the galaxy," explained team member Subhajit Sarkar of Cardiff University. "We have obtained the most detailed spectrum of a habitable-zone sub-Neptune to date, and this allowed us to work out the molecules that exist in its atmosphere."

Characterizing the atmospheres of exoplanets like K2-18 b -- meaning identifying their gases and physical conditions -- is a very active area in astronomy. However, these planets are outshone -- literally -- by the glare of their much larger parent stars, which makes exploring exoplanet atmospheres particularly challenging.

The team sidestepped this challenge by analyzing light from K2-18 b's parent star as it passed through the exoplanet's atmosphere. K2-18 b is a transiting exoplanet, meaning that we can detect a drop in brightness as it passes across the face of its host star. This is how the exoplanet was first discovered in 2015 with NASA's K2 mission. This means that during transits a tiny fraction of starlight will pass through the exoplanet's atmosphere before reaching telescopes like Webb. The starlight's passage through the exoplanet atmosphere leaves traces that astronomers can piece together to determine the gases of the exoplanet's atmosphere.

"This result was only possible because of the extended wavelength range and unprecedented sensitivity of Webb, which enabled robust detection of spectral features with just two transits," said Madhusudhan. "For comparison, one transit observation with Webb provided comparable precision to eight observations with Hubble conducted over a few years and in a relatively narrow wavelength range."

"These results are the product of just two observations of K2-18 b, with many more on the way," explained team member Savvas Constantinou of the University of Cambridge. "This means our work here is but an early demonstration of what Webb can observe in habitable-zone exoplanets."

The team's results were accepted for publication in The Astrophysical Journal Letters.

The team now intends to conduct follow-up research with the telescope's MIRI (Mid-Infrared Instrument) spectrograph that they hope will further validate their findings and provide new insights into the environmental conditions on K2-18 b.

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New catalyst lowers cost for producing environmentally sustainable hydrogen from water

A plentiful supply of clean energy is lurking in plain sight. It is the hydrogen we can extract from water (H2O) using renewable energy. Scientists are seeking low-cost methods for producing clean hydrogen from water to replace fossil fuels, as part of the quest to combat climate change.

Hydrogen can power vehicles while emitting nothing but water. Hydrogen is also an important chemical for many industrial processes, most notably in steel making and ammonia production. Using cleaner hydrogen is highly desirable in those industries.

A multi-institutional team led by the U.S. Department of Energy's (DOE) Argonne National Laboratory has developed a low-cost catalyst for a process that yields clean hydrogen from water. Other contributors include DOE's Sandia National Laboratories and Lawrence Berkeley National Laboratory, as well as Giner Inc.

"A process called electrolysis produces hydrogen and oxygen from water and has been around for more than a century," said Di-Jia Liu, senior chemist at Argonne. He also holds a joint appointment in the Pritzker School of Molecular Engineering at the University of Chicago.

Proton exchange membrane (PEM) electrolyzers represent a new generation of technology for this process. They can split water into hydrogen and oxygen with higher efficiency at near room temperature. The reduced energy demand makes them an ideal choice for producing clean hydrogen by using renewable but intermittent sources, such as solar and wind.

This electrolyzer runs with separate catalysts for each of its electrodes (cathode and anode). The cathode catalyst yields hydrogen, while the anode catalyst forms oxygen. A problem is that the anode catalyst uses iridium, which has a current market price of around $5,000 per ounce. The lack of supply and high cost of iridium pose a major barrier for widespread adoption of PEM electrolyzers.

The main ingredient in the new catalyst is cobalt, which is substantially cheaper than iridium. "We sought to develop a low-cost anode catalyst in a PEM electrolyzer that generates hydrogen at high throughput while consuming minimal energy," Liu said. "By using the cobalt-based catalyst prepared by our method, one could remove the main bottleneck of cost to producing clean hydrogen in an electrolyzer."

Giner Inc., a leading research and development company working toward commercialization of electrolyzers and fuel cells, evaluated the new catalyst using its PEM electrolyzer test stations under industrial operating conditions. The performance and durability far exceeded that of competitors' catalysts.

Important to further advancing the catalyst performance is understanding the reaction mechanism at the atomic scale under electrolyzer operating conditions. The team deciphered critical structural changes that occur in the catalyst under operating conditions by using X-ray analyses at the Advanced Photon Source (APS) at Argonne. They also identified key catalyst features using electron microscopy at Sandia Labs and at Argonne's Center for Nanoscale Materials (CNM). The APS and CNM are both DOE Office of Science user facilities.

"We imaged the atomic structure on the surface of the new catalyst at various stages of preparation," said Jianguo Wen, an Argonne materials scientist.

In addition, computational modeling at Berkeley Lab revealed important insights into the catalyst's durability under reaction conditions.

The team's achievement is a step forward in DOE's Hydrogen Energy Earthshot initiative, which mimics the U.S. space program's "Moon Shot" of the 1960s. Its ambitious goal is to lower the cost for green hydrogen production to one dollar per kilogram in a decade. Production of green hydrogen at that cost could reshape the nation's economy. Applications include the electric grid, manufacturing, transportation and residential and commercial heating.

"More generally, our results establish a promising path forward in replacing catalysts made from expensive precious metals with elements that are much less expensive and more abundant," Liu noted.

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How did Earth get its water?

Our planet's water could have originated from interactions between the hydrogen-rich atmospheres and magma oceans of the planetary embryos that comprised Earth's formative years, according to new work from Carnegie Science's Anat Shahar and UCLA's Edward Young and Hilke Schlichting. Their findings, which could explain the origins of Earth's signature features, are published in Nature.

For decades, what researchers knew about planet formation was based primarily on our own Solar System. Although there are some active debates about the formation of gas giants like Jupiter and Saturn, it is widely agreed upon that Earth and the other rocky planets accreted from the disk of dust and gas that surrounded our Sun in its youth.

As increasingly larger objects crashed into each other, the baby planetesimals that eventually formed Earth grew both larger and hotter, melting into a vast magma ocean due to the heat of collisions and radioactive elements. Over time, as the planet cooled, the densest material sank inward, separating Earth into three distinct layers -- the metallic core, and the rocky, silicate mantle and crust.

However, the explosion of exoplanet research over the past decade informed a new approach to modeling the Earth's embryonic state.

"Exoplanet discoveries have given us a much greater appreciation of how common it is for just-formed planets to be surrounded by atmospheres that are rich in molecular hydrogen, H2, during their first several million years of growth," Shahar explained. "Eventually these hydrogen envelopes dissipate, but they leave their fingerprints on the young planet's composition."

Using this information, the researchers developed new models for Earth's formation and evolution to see if our home planet's distinct chemical traits could be replicated.

Using a newly developed model, the Carnegie and UCLA researchers were able to demonstrate that early in Earth's existence, interactions between the magma ocean and a molecular hydrogen proto-atmosphere could have given rise to some of Earth's signature features, such as its abundance of water and its overall oxidized state.

The researchers used mathematical modeling to explore the exchange of materials between molecular hydrogen atmospheres and magma oceans by looking at 25 different compounds and 18 different types of reactions -- complex enough to yield valuable data about Earth's possible formative history, but simple enough to interpret fully.

Interactions between the magma ocean and the atmosphere in their simulated baby Earth resulted in the movement of large masses of hydrogen into the metallic core, the oxidation of the mantle, and the production of large quantities of water.

Even if all of the rocky material that collided to form the growing planet was completely dry, these interactions between the molecular hydrogen atmosphere and the magma ocean would generate copious amounts of water, the researchers revealed. Other water sources are possible, they say, but not necessary to explain Earth's current state.

"This is just one possible explanation for our planet's evolution, but one that would establish an important link between Earth's formation history and the most common exoplanets that have been discovered orbiting distant stars, which are called Super-Earths and sub-Neptunes," Shahar concluded.

This project was part of the interdisciplinary, multi-institution AEThER project, initiated and led by Shahar, which seeks to reveal the chemical makeup of the Milky Way galaxy's most common planets -- Super-Earths and sub-Neptunes -- and to develop a framework for detecting signatures of life on distant worlds. Funded by the Alfred P. Sloan Foundation, this effort was developed to understand how the formation and evolution of these planets shape their atmospheres. This could -- in turn -- enable scientists to differentiate true biosignatures, which could only be produced by the presence of life, from atmospheric molecules of non-biological origin.

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Switching to hydrogen fuel could prolong the methane problem

Hydrogen's potential as a clean fuel could be limited by a chemical reaction in the lower atmosphere, according to research from Princeton University and the National Oceanic and Atmospheric Association.

This is because hydrogen gas easily reacts in the atmosphere with the same molecule primarily responsible for breaking down methane, a potent greenhouse gas. If hydrogen emissions exceed a certain threshold, that shared reaction will likely lead to methane accumulating in the atmosphere -- with decades-long climate consequences.

"Hydrogen is theoretically the fuel of the future," said Matteo Bertagni, a postdoctoral researcher at the High Meadows Environmental Institute working on the Carbon Mitigation Initiative. "In practice, though, it poses many environmental and technological concerns that still need to be addressed."

Bertagni is the first author of a research article published in Nature Communications, in which researchers modeled the effect of hydrogen emissions on atmospheric methane. They found that above a certain threshold, even when replacing fossil fuel usage, a leaky hydrogen economy could cause near-term environmental harm by increasing the amount of methane in the atmosphere. The risk for harm is compounded for hydrogen production methods using methane as an input, highlighting the critical need to manage and minimize emissions from hydrogen production.

"We have a lot to learn about the consequences of using hydrogen, so the switch to hydrogen, a seemingly clean fuel, doesn't create new environmental challenges," said Amilcare Porporato, Thomas J. Wu '94 Professor of Civil and Environmental Engineering and the High Meadows Environmental Institute. Porporato is a principal investigator and member of the Leadership Team for the Carbon Mitigation Initiative and is also associated faculty at the Andlinger Center for Energy and the Environment.

The problem boils down to one small, difficult-to-measure molecule known as the hydroxyl radical (OH). Often dubbed "the detergent of the troposphere," OH plays a critical role in eliminating greenhouse gases such as methane and ozone from the atmosphere.

The hydroxyl radical also reacts with hydrogen gas in the atmosphere. And since a limited amount of OH is generated each day, any spike in hydrogen emissions means that more OH would be used to break down hydrogen, leaving less OH available to break down methane. As a consequence, methane would stay longer in the atmosphere, extending its warming impacts.

According to Bertagni, the effects of a hydrogen spike that might occur as government incentives for hydrogen production expand could have decades-long climate consequences for the planet.

"If you emit some hydrogen into the atmosphere now, it will lead to a progressive build-up of methane in the following years," Bertagni said. "Even though hydrogen only has a lifespan of around two years in the atmosphere, you'll still have the methane feedback from that hydrogen in 30 years from now."

In the study, the researchers identified the tipping point at which hydrogen emissions would lead to an increase in atmospheric methane and thereby undermine some of the near-term benefits of hydrogen as a clean fuel. By identifying that threshold, the researchers established targets for managing hydrogen emissions.

"It's imperative that we are proactive in establishing thresholds for hydrogen emissions, so that they can be used to inform the design and implementation of future hydrogen infrastructure," said Porporato.

For hydrogen referred to as green hydrogen, which is produced by splitting water into hydrogen and oxygen using electricity from renewable sources, Bertagni said that the critical threshold for hydrogen emissions sits at around 9%. That means that if more than 9% of the green hydrogen produced leaks into the atmosphere -- whether that be at the point of production, sometime during transport, or anywhere else along the value chain -- atmospheric methane would increase over the next few decades, canceling out some of the climate benefits of switching away from fossil fuels.

And for blue hydrogen, which refers to hydrogen produced via methane reforming with subsequent carbon capture and storage, the threshold for emissions is even lower. Because methane itself is the primary input for the process of methane reforming, blue hydrogen producers have to consider direct methane leakage in addition to hydrogen leakage. For example, the researchers found that even with a methane leakage rate as low as 0.5%, hydrogen leakages would have to be kept under around 4.5% to avoid increasing atmospheric methane concentrations.

"Managing leakage rates of hydrogen and methane will be critical," Bertagni said. "If you have just a small amount of methane leakage and a bit of hydrogen leakage, then the blue hydrogen that you produce really might not be much better than using fossil fuels, at least for the next 20 to 30 years."

The researchers emphasized the importance of the time scale over which the effect of hydrogen on atmospheric methane is considered. Bertagni said that in the long-term (over the course of a century, for instance), the switch to a hydrogen economy would still likely deliver net benefits to the climate, even if methane and hydrogen leakage levels are high enough to cause near-term warming. Eventually, he said, atmospheric gas concentrations would reach a new equilibrium, and the switch to a hydrogen economy would demonstrate its climate benefits. But before that happens, the potential near-term consequences of hydrogen emissions might lead to irreparable environmental and socioeconomic damage.

Thus, if institutions hope to meet mid-century climate goals, Bertagni cautioned that hydrogen and methane leakage to the atmosphere must be held in check as hydrogen infrastructure begins to roll out. And because hydrogen is a small molecule that is notoriously difficult to control and measure, he explained that managing emissions will likely require researchers to develop better methods for tracking hydrogen losses across the value chain.

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Catalyst purifies herbicide-tainted water and produces hydrogen

Researchers in the Oregon State University College of Science have developed a dual-purpose catalyst that purifies herbicide-tainted water while also producing hydrogen.

The project, which included researchers from the OSU College of Engineering and HP Inc. is important because water pollution is a major global challenge, and hydrogen is a clean, renewable fuel.

Findings of the study, which explored photoactive catalysts, were published today in the journal ACS Catalysis.

"We can combine oxidation and reduction into a single process to achieve an efficient photocatalytic system," OSU's Kyriakos Stylianou said. "Oxidation happens via a photodegradation reaction, and reduction through a hydrogen evolution reaction."

A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

Photocatalysts are materials that absorb light to reach a higher energy level and can use that energy to break down organic contaminants through oxidation. Among photocatalysts' many applications are self-cleaning coatings for stain- and odor-resistant walls, floors, ceilings and furniture.

Stylianou, assistant professor of chemistry, led the study, which involved titanium dioxide photocatalysts derived from a metal-organic framework, or MOF.

Made up of positively charged metal ions surrounded by organic "linker" molecules, MOFs are crystalline, porous materials with tunable structural properties and nanosized pores. They can be designed with a variety of components that determine the MOF's properties.

Upon MOFs' calcination -- high heating without melting -- semiconducting materials like titanium dioxide can be generated. Titanium dioxide is the most commonly used photocatalyst, and it's found in the minerals anatase, rutile and brookite.

Stylianou and collaborators including Líney Árnadóttir of the OSU College of Engineering and William Stickle of HP discovered that anatase doped with nitrogen and sulfur was the best "two birds, one stone" photocatalyst for simultaneously producing hydrogen and degrading the heavily used herbicide glyphosate.

Glyphosate, also known as N-phosphonomethyl glycine or PMG, has been widely sprayed on agricultural fields over the last 50 years since first appearing on the market under the trade name Roundup.

"Only a small percentage of the total amount of PMG applied is taken up by crops, and the rest reaches the environment," Stylianou said. "That causes concerns regarding the leaching of PMG into soil and groundwater, as well it should -- contaminated water can be detrimental to the health of every living thing on the planet. And herbicides leaching into water channels are a primary cause of water pollution."

Among an array of compounds in which hydrogen is found, water is the most common, and producing hydrogen by splitting water via photocatalysis is cleaner and more sustainable than the conventional method of deriving hydrogen -- from natural gas via a carbon-dioxide-producing process known as methane-steam reforming.

Hydrogen serves many scientific and industrial purposes in addition to its energy-related roles. It's used in fuel cells for cars, in the manufacture of many chemicals including ammonia, in the refining of metals and in the production of plastics.

"Water is a rich hydrogen source, and photocatalysis is a way of tapping into the Earth's abundant solar energy for hydrogen production and environmental remediation," Stylianou said. "We are showing that through photocatalysis, it is possible to produce a renewable fuel while removing organic pollutants, or converting them into useful products."

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Does ice in the Universe contain the molecules making up the building blocks of life in planetary systems?

The James Webb Space Telescope -- the most precise telescope ever built -- was decisive in discovering the frozen forms of a long series of molecules, such as carbon dioxide, ammonia, methane, methanol and even more complex molecules, frozen out as ices on the surface of small dust grains.

The dust grains grow in size when being a part of the discs of gas and dust forming around young stars. This means that the researchers could study many of the molecules going into the forming of new exoplanets.

Researchers at the Niels Bohr Institute, University of Copenhagen, combined the discoveries from JWST with data from Atacama Large Millimeter Array (ALMA), making observations in other wavelengths than JWST and researchers from Aarhus University contributed with the necessary investigations in the laboratory.

"With the application of observations, e.g. from ALMA, it is possible for us to directly observe the dust grains themselves, and it is also possible to see the same molecules as in the gas observed in the ice" Lars Kristensen, associate Professor at the Niels Bohr Institute (NBI), explains.

"Using the combined data set gives us a unique insight into the complex interactions between gas, ice and dust in areas where stars and planets form" according to Jes Jørgensen, Professor at NBI.

"This way we can map the location of the molecules in the area both before and after they have been frozen out onto the dust grains and we can follow their path from the cold molecular cloud to the emerging planetary systems around young stars."

The content of ice in the molecular cloud was a decisive discovery

The ices were detected and measured by studying how starlight from beyond the molecular cloud was absorbed by icy molecules at specific infrared wavelengths visible to Webb.

This process leaves behind chemical fingerprints known as absorption spectra which can be compared with laboratory data to identify which ices are present in the molecular cloud.

In this study, the team targeted ices buried in a particularly cold, dense and difficult to investigate region of the Chamaeleon I molecular cloud, a region approximately 600 light-years from Earth which is currently in the process of forming dozens of young stars.

Along with star forming comes planet forming and the perspective for the researchers in the IceAge collaboration is basically to identify the role the ice plays in gathering the molecules necessary to form life.

"This study confirms that interstellar grains of dust are catalysts for the forming of complex molecules in the very diffuse gas in these clouds, something we see in the lab as well," Sergio Ioppolo explains, associate professor at Aarhus University, contributing with some of the experiments in the lab that were compared with the observations.

The sensitivity of JWST was an absolutely necessary precondition for the discovery

"We simply couldn't have observed these ices without Webb," elaborated Klaus Pontoppidan, JWST project scientist at the Space Telescope Science Institute, Baltimore, USA, who was involved in this research.

"The ices show up as dips against a continuum of background starlight. In regions that are this cold and dense, much of the light from the background star is blocked and Webb's exquisite sensitivity was necessary to detect the starlight and therefore identify the ices in the molecular cloud."

The IceAge team has already planned more observations with both Webb and other telescopes.

"These observations together with further laboratory studies will tell us which mixture of ices -- and therefore which elements -- can eventually be delivered to the surfaces of terrestrial exoplanets or incorporated into the atmospheres of giant gas or ice planets.

Read more at Science Daily

Why microbes in the deep ocean live without sunlight

A world first study reverses the idea that the bulk of life in the ocean is fuelled by photosynthesis via sunshine, revealing that many ocean microbes in fact get their energy from hydrogen and carbon monoxide.

It has always been a mystery as to how microbes growing in deepest parts of the sea survive, with no sunlight. A new study, from researchers at the Monash University published in the journal Nature Microbiology, shows that a distinct process called chemosynthesis -- growth using inorganic compounds -- fuels microbes in these darkest depths.

The five-year study, led by Dr Rachael Lappan and Professor Chris Greening from the Biomedicine Discovery Institute, reveals that two common gases -- hydrogen and carbon monoxide -- serve as the fuel for trillions of microbes in the ocean from the tropics to the poles.

According to Professor Greening, until now most scientists have believed that ocean microbial life is primarily driven by photosynthesis (growth by using light energy). "But what about those regions so deep that light can't penetrate or so nutrient-poor that algae can't thrive? We showed in this study that instead chemosynthesis is dominant in these regions," he said.

"Hydrogen and carbon monoxide in fact "fed" microbes in all regions we've looked at: from urban bays to around tropical islands to hundreds of metres below the surface. Some can even be found beneath Antarctica's ice shelves."

The study involved combining chemical measurements during oceanic voyages with laboratory-based characterisation of microbial cultures. The research team also extensively used metagenomic sequencing, "which tells us the genetic blueprints of all of the microbes present in a given region of the ocean," Dr Lappan said. "We found the genes that enable hydrogen consumption across eight distantly related types of microbes, known as phyla, and this survival strategy becomes more common the deeper they live."

For this project, the researchers were inspired by their previous work on soil bacteria. Professor Greening and colleagues have previously showed most soil bacteria can live by consuming hydrogen and carbon monoxide from the atmosphere.

"The surface layers of the world's oceans generally contain high levels of dissolved hydrogen and carbon monoxide gases due to various geological and biological processes. So it made sense that oceanic bacteria used the same gases as their terrestrial cousins," Dr Lappan said.

Read more at Science Daily

Seawater split to produce 'green' hydrogen

Researchers have successfully split seawater without pre-treatment to produce green hydrogen.

The international team was led by the University of Adelaide's Professor Shizhang Qiao and Associate Professor Yao Zheng from the School of Chemical Engineering.

"We have split natural seawater into oxygen and hydrogen with nearly 100 per cent efficiency, to produce green hydrogen by electrolysis, using a non-precious and cheap catalyst in a commercial electrolyser," said Professor Qiao.

A typical non-precious catalyst is cobalt oxide with chromium oxide on its surface.

"We used seawater as a feedstock without the need for any pre-treatment processes like reverse osmosis desolation, purification, or alkalisation," said Associate Professor Zheng.

"The performance of a commercial electrolyser with our catalysts running in seawater is close to the performance of platinum/iridium catalysts running in a feedstock of highly purified deionised water.

The team published their research in the journal Nature Energy.

"Current electrolysers are operated with highly purified water electrolyte. Increased demand for hydrogen to partially or totally replace energy generated by fossil fuels will significantly increase scarcity of increasingly limited freshwater resources," said Associate Professor Zheng.

Seawater is an almost infinite resource and is considered a natural feedstock electrolyte. This is more practical for regions with long coastlines and abundant sunlight. However, it isn't practical for regions where seawater is scarce.

Seawater electrolysis is still in early development compared with pure water electrolysis because of electrode side reactions, and corrosion arising from the complexities of using seawater.

"It is always necessary to treat impure water to a level of water purity for conventional electrolysers including desalination and deionisation, which increases the operation and maintenance cost of the processes," said Associate Professor Zheng.

"Our work provides a solution to directly utilise seawater without pre-treatment systems and alkali addition, which shows similar performance as that of existing metal-based mature pure water electrolyser."

The team will work on scaling up the system by using a larger electrolyser so that it can be used in commercial processes such as hydrogen generation for fuel cells and ammonia synthesis.

Researchers have successfully split seawater without pre-treatment to produce green hydrogen.

The international team was led by the University of Adelaide's Professor Shizhang Qiao and Associate Professor Yao Zheng from the School of Chemical Engineering.

"We have split natural seawater into oxygen and hydrogen with nearly 100 per cent efficiency, to produce green hydrogen by electrolysis, using a non-precious and cheap catalyst in a commercial electrolyser," said Professor Qiao.

A typical non-precious catalyst is cobalt oxide with chromium oxide on its surface.

"We used seawater as a feedstock without the need for any pre-treatment processes like reverse osmosis desolation, purification, or alkalisation," said Associate Professor Zheng.

"The performance of a commercial electrolyser with our catalysts running in seawater is close to the performance of platinum/iridium catalysts running in a feedstock of highly purified deionised water.

The team published their research in the journal Nature Energy.

"Current electrolysers are operated with highly purified water electrolyte. Increased demand for hydrogen to partially or totally replace energy generated by fossil fuels will significantly increase scarcity of increasingly limited freshwater resources," said Associate Professor Zheng.

Seawater is an almost infinite resource and is considered a natural feedstock electrolyte. This is more practical for regions with long coastlines and abundant sunlight. However, it isn't practical for regions where seawater is scarce.

Seawater electrolysis is still in early development compared with pure water electrolysis because of electrode side reactions, and corrosion arising from the complexities of using seawater.

"It is always necessary to treat impure water to a level of water purity for conventional electrolysers including desalination and deionisation, which increases the operation and maintenance cost of the processes," said Associate Professor Zheng.

"Our work provides a solution to directly utilise seawater without pre-treatment systems and alkali addition, which shows similar performance as that of existing metal-based mature pure water electrolyser."

Read more at Science Daily

Martian meteorite upsets planet formation theory

A new study of an old meteorite contradicts current thinking about how rocky planets like the Earth and Mars acquire volatile elements such as hydrogen, carbon, oxygen, nitrogen and noble gases as they form. The work is published June 16 in Science.

A basic assumption about planet formation is that planets first collect these volatiles from the nebula around a young star, said Sandrine Péron, a postdoctoral scholar working with Professor Sujoy Mukhopadhyay in the Department of Earth and Planetary Sciences, University of California, Davis.

Because the planet is a ball of molten rock at this point, these elements initially dissolve into the magma ocean and then degass back into the atmosphere. Later on, chondritic meteorites crashing into the young planet deliver more volatile materials.

So scientists expect that the volatile elements in the interior of the planet should reflect the composition of the solar nebula, or a mixture of solar and meteoritic volatiles, while the volatiles in the atmosphere would come mostly from meteorites. These two sources -- solar vs. chondritic -- can be distinguished by the ratios of isotopes of noble gases, in particular krypton.

Mars is of special interest because it formed relatively quickly -- solidifying in about 4 million years after the birth of the Solar System, while the Earth took 50 to 100 million years to form.

"We can reconstruct the history of volatile delivery in the first few million years of the Solar System," Péron said.

Meteorite from Mars' interior

Some meteorites that fall to Earth come from Mars. Most come from surface rocks that have been exposed to Mars' atmosphere. The Chassigny meteorite, which fell to Earth in north-eastern France in 1815, is rare and unusual because it is thought to represent the interior of the planet.

By making extremely careful measurements of minute quantities of krypton isotopes in samples of the meteorite using a new method set up at the UC Davis Noble Gas Laboratory, the researchers could deduce the origin of elements in the rock.

"Because of their low abundance, krypton isotopes are challenging to measure," Péron said.

Surprisingly, the krypton isotopes in the meteorite correspond to those from chondritic meteorites, not the solar nebula. That means that meteorites were delivering volatile elements to the forming planet much earlier than previously thought, and in the presence of the nebula, reversing conventional thinking.

"The Martian interior composition for krypton is nearly purely chondritic, but the atmosphere is solar," Péron said. "It's very distinct."

The results show that Mars' atmosphere cannot have formed purely by outgassing from the mantle, as that would have given it a chondritic composition. The planet must have acquired atmosphere from the solar nebula, after the magma ocean cooled, to prevent substantial mixing between interior chondritic gases and atmospheric solar gases.

The new results suggest that Mars' growth was completed before the solar nebula was dissipated by radiation from the Sun. But the irradiation should also have blown off the nebular atmosphere on Mars, suggesting that atmospheric krypton must have somehow been preserved, possibly trapped underground or in polar ice caps.

"However, that would require Mars to have been cold in the immediate aftermath of its accretion," Mukhopadhyay said. "While our study clearly points to the chondritic gases in the Martian interior, it also raises some interesting questions about the origin and composition of Mars' early atmosphere."

Read more at Science Daily