Day: 08/28/2015

Artificial leaf harnesses sunlight for efficient fuel production

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A highly efficient photoelectrochemical (PEC) device uses the power of the sun to split water into hydrogen and oxygen. The stand-alone prototype includes two chambers separated by a semi-permeable membrane that allows collection of both gas products.
Credit: Lance Hayashida/Caltech

Generating and storing renewable energy, such as solar or wind power, is a key barrier to a clean-energy economy. When the Joint Center for Artificial Photosynthesis (JCAP) was established at Caltech and its partnering institutions in 2010, the U.S. Department of Energy (DOE) Energy Innovation Hub had one main goal: a cost-effective method of producing fuels using only sunlight, water, and carbon dioxide, mimicking the natural process of photosynthesis in plants and storing energy in the form of chemical fuels for use on demand. Over the past five years, researchers at JCAP have made major advances toward this goal, and they now report the development of the first complete, efficient, safe, integrated solar-driven system for splitting water to create hydrogen fuels.

“This result was a stretch project milestone for the entire five years of JCAP as a whole, and not only have we achieved this goal, we also achieved it on time and on budget,” says Caltech’s Nate Lewis, George L. Argyros Professor and professor of chemistry, and the JCAP scientific director.

The new solar fuel generation system, or artificial leaf, is described in the August 24 online issue of the journal Energy and Environmental Science. The work was done by researchers in the laboratories of Lewis and Harry Atwater, director of JCAP and Howard Hughes Professor of Applied Physics and Materials Science.

“This accomplishment drew on the knowledge, insights and capabilities of JCAP, which illustrates what can be achieved in a Hub-scale effort by an integrated team,” Atwater says. “The device reported here grew out of a multi-year, large-scale effort to define the design and materials components needed for an integrated solar fuels generator.”

The new system consists of three main components: two electrodes–one photoanode and one photocathode–and a membrane. The photoanode uses sunlight to oxidize water molecules, generating protons and electrons as well as oxygen gas. The photocathode recombines the protons and electrons to form hydrogen gas. A key part of the JCAP design is the plastic membrane, which keeps the oxygen and hydrogen gases separate. If the two gases are allowed to mix and are accidentally ignited, an explosion can occur; the membrane lets the hydrogen fuel be separately collected under pressure and safely pushed into a pipeline.

Semiconductors such as silicon or gallium arsenide absorb light efficiently and are therefore used in solar panels. However, these materials also oxidize (or rust) on the surface when exposed to water, so cannot be used to directly generate fuel. A major advance that allowed the integrated system to be developed was previous work in Lewis’s laboratory, which showed that adding a nanometers-thick layer of titanium dioxide (TiO2)–a material found in white paint and many toothpastes and sunscreens–onto the electrodes could prevent them from corroding while still allowing light and electrons to pass through. The new complete solar fuel generation system developed by Lewis and colleagues uses such a 62.5-nanometer-thick TiO2 layer to effectively prevent corrosion and improve the stability of a gallium arsenide-based photoelectrode.

Another key advance is the use of active, inexpensive catalysts for fuel production. The photoanode requires a catalyst to drive the essential water-splitting reaction. Rare and expensive metals such as platinum can serve as effective catalysts, but in its work the team discovered that it could create a much cheaper, active catalyst by adding a 2-nanometer-thick layer of nickel to the surface of the TiO2. This catalyst is among the most active known catalysts for splitting water molecules into oxygen, protons, and electrons and is a key to the high efficiency displayed by the device.

The photoanode was grown onto a photocathode, which also contains a highly active, inexpensive, nickel-molybdenum catalyst, to create a fully integrated single material that serves as a complete solar-driven water-splitting system.

A critical component that contributes to the efficiency and safety of the new system is the special plastic membrane that separates the gases and prevents the possibility of an explosion, while still allowing the ions to flow seamlessly to complete the electrical circuit in the cell. All of the components are stable under the same conditions and work together to produce a high-performance, fully integrated system. The demonstration system is approximately one square centimeter in area, converts 10 percent of the energy in sunlight into stored energy in the chemical fuel, and can operate for more than 40 hours continuously.

“This new system shatters all of the combined safety, performance, and stability records for artificial leaf technology by factors of 5 to 10 or more ,” Lewis says.

“Our work shows that it is indeed possible to produce fuels from sunlight safely and efficiently in an integrated system with inexpensive components,” Lewis adds, “Of course, we still have work to do to extend the lifetime of the system and to develop methods for cost-effectively manufacturing full systems, both of which are in progress.”

Because the work assembled various components that were developed by multiple teams within JCAP, coauthor Chengxiang Xiang, who is co-leader of the JCAP prototyping and scale-up project, says that the successful end result was a collaborative effort. “JCAP’s research and development in device design, simulation, and materials discovery and integration all funneled into the demonstration of this new device,” Xiang says.

Physicists discover ‘clearest evidence yet’ that the Universe is a hologram

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A team of physicists have provided what has been described by the journal Nature as the “clearest evidence yet” that our universe is a hologram.

The new research could help reconcile one of modern physics’ most enduring problems : the apparent inconsistencies between the different models of the universe as explained by quantum physics and Einstein’s theory of gravity.

The two new scientific papers are the culmination of years’ work led by Yoshifumi Hyakutake of Ibaraki University in Japan, and deal with hypothetical calculations of the energies of black holes in different universes.

The idea of the universe existing as a ‘hologram’ doesn’t refer to a Matrix-like illusion, but the theory that the three dimensions we perceive are actually just“painted” onto the cosmological horizon – the boundary of the known universe.

If this sounds paradoxical, try to imagine a holographic picture that changes as you move it. Although the picture is two dimensional, observing it from different locations creates the illusion that it is 3D.

This model of the universe helps explain some inconsistencies between general relativity (Einstein’s theory) and quantum physics. Although Einstein’s work underpins much of modern physics, at certain extremes (such as in the middle of a black hole) the principles he outlined break down and the laws of quantum physics take over.

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The traditional method of reconciling these two models has come from the 1997 work of theoretical physicist Juan Maldacena, whose ideas built upon string theory.

This is one of the most well respected ‘theories of everything’(Stephen Hawking is a fan) and it posits that one-dimensional vibrating objects known as ‘strings’ are the elementary particles of the universe.

Maldacena has welcomed the new research by Hyakutake and his team, telling the journal Nature that the findings are “an interesting way to test many ideas in quantum gravity and string theory.”

Leonard Susskind, a theoretical physicist regarded as one of the fathers of string theory, added that the work by the Japanese team “numerically confirmed, perhaps for the first time, something we were fairly sure had to be true, but was still a conjecture.”

Alzheimer’s disease thought to be accelerated by an abnormal build-up of fat in the brain

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Alzheimer's disease thought to be accelerated by an abnormal build-up of fat in the brain
People with Alzheimer’s disease have fat deposits in the brain. For the first time since the disease was described 109 years ago, researchers affiliated with the University of Montreal Hospital Research Centre (CRCHUM) have discovered accumulations of fat droplets in the brain of patients who died from the disease and have identified the nature of the fat. 

People with Alzheimer’s disease have fat deposits in the brain. For the first time since the disease was described 109 years ago, researchers affiliated with the University of Montreal Hospital Research Centre (CRCHUM) have discovered accumulations of fat droplets in the brain of patients who died from the disease and have identified the nature of the fat.

This breakthrough, published today in the journal Cell Stem Cell, opens up a new avenue in the search for a medication to cure or slow the progression of Alzheimer’s . “We found fatty acid deposits in the brain of patients who died from the disease and in mice that were genetically modified to develop Alzheimer’s disease. Our experiments suggest that these abnormal fat deposits could be a trigger for the disease”, said Karl Fernandes, a researcher at the CRCHUM and a professor at University of Montreal.

Over 47.5 million people worldwide have Alzheimer’s disease or some other type of dementia, according to the World Health Organization. Despite decades of research, the only medications currently available treat the symptoms alone.

This study highlights what might prove to be a missing link in the field. Researchers initially tried to understand why the brain’s stem cells, which normally help repair brain damage, are unresponsive in Alzheimer’s disease. Doctoral student Laura Hamilton was astonished to find near the stem cells, on the inner surface of the brain in mice predisposed to develop the disease. “We realized that Dr. Alois Alzheimer himself had noted the presence of lipid accumulations in patients’ brains after their death when he first described the disease in 1906. But this observation was dismissed and largely forgotten due to the complexity of lipid biochemistry”, said Laura Hamilton.

The researchers examined the brains of nine patients who died from Alzheimer’s disease and found significantly more fat droplets compared with five healthy brains. A team of chemists from University of Montreal led by Pierre Chaurand then used an advanced mass spectrometry technique to identify these fat deposits as triglycerides enriched with specific , which can also be found in animal fats and vegetable oils.

“We discovered that these fatty acids are produced by the brain, that they build up slowly with normal aging, but that the process is accelerated significantly in the presence of genes that predispose to Alzheimer’s disease”, explained Karl Fernandes. In mice predisposed to the disease, we showed that these fatty acids accumulate very early on, at two months of age, which corresponds to the early twenties in humans. Therefore, we think that the build-up of fatty acids is not a consequence but rather a cause or accelerator of the disease.”

Fortunately, there are pharmacological inhibitors of the enzyme that produces these fatty acids. These molecules, which are currently being tested for metabolic diseases such as obesity, could be effective in treating Alzheimer’s disease. “We succeeded in preventing these fatty acids from building up in the brains of mice predisposed to the disease. The impact of this treatment on all the aspects of the disease is not yet known, but it significantly increased stem cell activity,” explained Karl Fernandes. “This is very promising because play an important role in learning, memory and regeneration.”

This discovery lends support to the argument that Alzheimer’s disease is a metabolic brain disease, rather like obesity or diabetes are peripheral metabolic diseases. Karl Fernandes’ team is continuing its experiments to verify whether this new approach can prevent or delay the problems with memory, learning and depression associated with the disease.

Bioactive Compound In Turmeric Regenerates Brain Stem Cells .

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Components of turmeric – a well-known ingredient in curry spice – are wildly studied today for its anti-inflammatory effects and cancer prevention.

It turns out, a lesser-known bioactive turmeric compound promotes stem cell proliferation and differentiation in the brain, according to new research recently published in the open access journal Stem Cell Research & Therapy.

Results suggest aromatic turmerone could be a potential for treating neurological disorders, such as stroke and Alzheimer’s disease. Of course, the potential for researchers lies in its becoming a future drug candidate.

The study looked at the effects of aromatic (ar-) turmerone on endogenous neutral stem cells (NSC), which are stem cells found within adult brains.

NSC differentiate into neurons, and play an important role in self-repair and recovery of brain function in neurodegenerative diseases. Previous studies of ar-turmerone have shown that the compound can block activation of microglia cells – which are a part of central nervous system immune defense. When activated, these cells cause neuroinflammation, which is associated with different neurological disorders. However, ar-turmerone’s impact on the brain’s capacity to self-repair was unknown.

Researchers from the Institute of Neuroscience and Medicine in Jülich, Germany, studied the effects of ar-turmerone on NSC proliferation and differentiation both in vitro and in vivo.

In vitro: Rat fetal NSC were cultured and grown in six different concentrations of ar-turmerone over a 72 hour period. At certain concentrations, ar-turmerone was shown to increase NSC proliferation by up to 80%, without having any impact on cell death. The cell differentiation process also accelerated in ar-turmerone-treated cells compared to untreated control cells.

To test the effects of ar-turmerone on NSC in vivo, the researchers injected adult rats with ar-turmerone. Using PET imaging and a tracer to detect proliferating cells, they found that the subventricular zone (SVZ) was wider, and the hippocampus expanded, in the brains of rats injected with ar-turmerone than in control animals. The SVZ and hippocampus are the two sites in adult mammalian brains where neurogenesis, the growth of neurons, is known to occur.

Lead author of the study, Adele Rueger, said:

While several substances have been described to promote stem cell proliferation in the brain, fewer drugs additionally promote the differentiation of stem cells into neurons, which constitutes a major goal in regenerative medicine. Our findings on aromatic turmerone take us one step closer to achieving this goal.

Of course, researchers are scrambling to isolate turmeric compounds to later produce patented pharmaceuticals. While their discoveries are a revelation, it shouldn’t diminish the power of consuming whole-food turmeric and letting all the compounds go to work.Inexpensive, bulk turmeric power can be easily found at the health food store or online.Tinctures are a concentrated form that can be taken in liquids, and capsules are preferableif the strong taste cannot be withstood.

This study shows that the anti-inflammatory benefits of turmeric extend to the brain and nervous system which could make it ideal in a diet to potentially help with neurodegenerative and auto-immune problems.

Physicists announce graphene’s latest cousin: stanene

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Physicists say they have produced stanene – a 2D layer of tin (Sn) atoms. It forms a honeycomb structure ‘buckled’ on top of a bismuth telluride support (centre: top view; right: side view). Microscope images pick out only the upper ridges of the sheet (left).

Two years after physicists predicted that tin should be able to form a mesh just one atom thick, researchers say that they have made it. The thin film, called stanene, is reported on 3 August inNature Materials1. But researchers have not been able to confirm whether the material has the predicted exotic electronic properties that have excited theorists, such as being able to conduct electricity without generating any waste heat.

Stanene (from the Latin stannum meaning tin, which also gives the element its chemical symbol, Sn), is the latest cousin of graphene, the honeycomb lattice of carbon atoms that has spurred thousands of studies into related 2D materials. Those include sheets of silicene, made from silicon atoms; phosphorene, made from phosphorus; germanene, from germanium; and thin stacks of sheets that combine different kinds of chemical elements (see ‘The super materials that could trump graphene’).

Many of these sheets are excellent conductors of electricity, but stanene is — in theory — extra-special. At room temperature, electrons should be able to travel along the edges of the mesh without colliding with other electrons and atoms as they do in most materials. This should allow the film to conduct electricity without losing energy as waste heat, according to predictions2 made in 2013 by Shou-Cheng Zhang, a physicist at Stanford University in California, who is a co-author of the latest study.

That means that a thin film of stanene might be the perfect highway along which to ferry current in electric circuits, says Peide Ye, a physicist and electrical engineer at Purdue University in West Lafayette, Indiana. “I’m always looking for something not only scientifically interesting but that has potential for applications in a device,” he says. “It’s very interesting work.”

Stanene is predicted to be an example of a topological insulator, in which charge carriers (such as electrons) cannot travel through a material’s centre but can move freely along its edge, with their direction of travel dependent on whether their spin — a quantum property — points ‘up’ or ‘down’. Electric current is not dissipated because most impurities do not affect the spin and cannot slow the electrons, says Zhang.

Substrate interference

But even after making stanene, Zhang and his colleagues at four universities in China have not been able to confirm that it is a topological insulator. Experimentalists at Shanghai Jiao Tong University created the mesh by vaporizing tin in a vacuum and allowing the atoms to waft onto a supporting surface made of bismuth telluride. Although this surface allows 2D stanene crystals to form, it also interacts with them, creating the wrong conditions for a topological insulator, says Zhang. He has already co-authored another paper3 examining which surfaces would work better.

Ralph Claessen, a physicist at the University of Würzburg in Germany, says that it is not completely clear that the researchers have made stanene. Theory predicts that the 2D tin lattice should form a buckled honeycomb structure, with alternate atoms folding upwards to form corrugated ridges; Zhang and his team mostly saw only the upper ridge of atoms with their scanning tunnelling microscope, except in a small spot where that ridge disappeared and a lower layer of tin atoms was exposed. However, they are confident that they have created a buckled honeycomb, partly because the distance between upper and lower layers matches predictions.

Claessen says that he would need to see direct measurements of the lattice’s structure — from X-ray diffraction — to be confident that the team has made stanene, and not some other arrangement of tin. This would require larger amounts of the material than Zhang and his co-authors have grown.

Yuanbo Zhang, a physicist at Fudan University in Shanghai, China, who was not involved in the study, is more convinced. “I think the work is a significant breakthrough that once again expands the 2D-material universe,” he says. “It’ll be exciting to see how the material lives up to its expectations.”

And Guy Le Lay, a physicist at Aix-Marseille University in France who was among the first to produce both silicene4 and germanene5, preaches optimism in the attempt to verify stanene’s electronic properties. “It’s like going to the Moon,” he says. “The first step is the crucial step.”

Researchers Thwart Cancer Cells By Triggering ‘Virus Alert’

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Working with human cancer cell lines and mice, researchers at the Johns Hopkins Kimmel Cancer Center and elsewhere have found a way to trigger a type of immune system “virus alert” that may one day boost cancer patients’ response to immunotherapy drugs. An increasingly promising focus of cancer research, the drugs are designed to disarm cancer cells’ ability to avoid detection and destruction by the immune system.

In a report on the work published in the Aug. 27 issue ofCell, the Johns Hopkins-led research team says it has found a core group of genes related to both a viral defense warning system and susceptibility to a demethylating drug called 5-azacytidine that chemically alters their ability to operate through a process called demethylation.

A study with similar findings authored by Daniel De Carvalho, Ph.D., at the Ontario Cancer Institute/Princess Margaret Hospital, and Peter Jones, Ph.D., D.Sc., director of research at the Van Andel Institute, focused on the ability of DNA demethylating agents to target colorectal cancer stem cells, is published in the same journal issue.

Tumors are known to co-opt cellular gene-silencing systems that add tiny chemicals called methyl groups to areas of genes, thereby turning off the affected gene function. Such “epigenetic” control normally occurs in many genes, including ones that contain DNA leftover from previous exposures to viruses. When epigenetic control of these genes is removed, the virus-laden gene sequences are activated and trigger an alert to immune system cells that a virus has invaded.

“A main barrier to immune therapy success has been the tumor’s ability to keep the immune system from functioning against the cancer,” says study leader Stephen Baylin, M.D., the Virginia and Daniel K. Ludwig Professor of Cancer Research at the Kimmel Cancer Center. “The immune cells are there, but like an unarmed army, they hang around and do nothing. However, certain epigenetic processes that silence such viral defense genes can be reversed in tumor cells with a demethylating drug, making immunotherapies work more effectively to kill cancer cells.”

For their new study, Baylin and his team worked with laboratory-grown cell lines from human ovarian, colon and skin cancer, and the team led by De Carvalho worked with colon cancer cells. In the cancer cell lines, both teams found that the viral defense pathway can be turned on when the cells were exposed to 5-azacytidine. Once the pathway is activated, Baylin adds, the tumor cells release signaling proteins called interferons that rouse other cancer-fighting cells in the immune system.

Then, the Johns Hopkins team created a gene signature of the viral defense pathway. In tumor samples available from the National Cancer Institute’s Cancer Genome Atlas project, the scientists used the gene signature to distinguish between tumor samples with high expression of the pathway from those with low expression. Those with high expression may respond to certain immunotherapy drugs without the aid of 5-azacytidine, but those with low expression levels may need the epigenetic drug to boost response to immunotherapy, says Baylin.

Looking for the connection between the pathway’s expression and immunotherapy drug response, the Johns Hopkins investigators and their colleagues focused on expression levels of the viral defense pathway in tumor cells from 21 patients with melanoma treated with the immune therapy drug ipilimumab at Memorial Sloan Kettering Cancer Center. They found high expression levels in the cells of seven of eight of those patients who had responded well to ipilimumab. Cells from all 12 patients with limited response to ipilimumab had low expression of the viral defense pathway.

In a melanoma mouse model in which ipilimumab alone was partially effective, adding 5-azacytidine to ipilimumab triggered a better tumor response.

“Our findings further decipher the mechanisms that lead to this tumor cell immune reaction and offer a way to potentially boost the success of immune therapies in patients with cancer,” says Baylin, who first became interested in the immune system’s connection to 5-azacytidine when laboratory research and clinical trials at Johns Hopkins hinted at the drug’s ability to prevent cancer cells’ proliferation when combined with immunotherapy.

Baylin and his colleagues say that, if their findings are confirmed and extended in clinical trials, the 5-azacytidine treatment could be followed by ipilimumab or other types of immunotherapy called checkpoint blockade, which lower cancer cells’ defenses and allow immune system cells to see and destroy them.

“Treatment with 5-azacytidine activates interferon signaling in tumor cells and, when followed by checkpoint blockade immune therapy, the immune cells could go into increased action against the cancer,” says Johns Hopkins research fellow and lead author Katherine Chiappinelli, Ph.D.

Baylin and Chiappinelli caution that clinical trials will take time to learn how effective the strategy of alerting the viral defense pathway might be. But the strategy holds promise, he says, for patients who have cancers with low expression of the pathway.

In addition to Baylin and Chiappinelli, other investigators included Pamela L. Strissel, Alexis Desrichard, Huili Li, Christine Henke, Benjamin Akman, Alexander Hein, Neal S. Rote, Leslie M. Cope, Alexandra Snyder, Vladimir Makarov, Sadna Buhu, Dennis Slamon, Jedd D. Wolchok, Drew M. Pardoll, Matthias W. Beckmann, Cynthia A. Zahnow, Taha Mergoub, Timothy A. Chan and Reiner Strick. In addition to the Johns Hopkins Kimmel Cancer Center, participating institutions included the University-Clinic Erlangen in Germany, Memorial Sloan Kettering Cancer Center, Case Western Reserve University and Jonsson Comprehensive Cancer Center at UCLA.

Baylin is a consultant for MDxHealth, which makes an assay procedure that is licensed to MDxHealth by The Johns Hopkins University. Baylin and the university are entitled to royalty shares from sales of the assay. Pardoll is a consultant for Pfizer and Amplimmune.

The Longest Tunnel In the World Is Now Finished

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​Earlier this week, the new longest tunnel in the world was completed. The Gotthard Base Tunnel started in 2004, and travels underneath the Swiss Alps for 35.4 miles. The cost of the project was just under $10 billion U.S., and now it is finally done, though it won’t see its first passenger trains until next year.

The Gotthard Base tunnel was constructed some 2,000 feet below an existing 10 mile tunnel that was opened in 1882. In addition to accommodating more trains through the mountain range on its two parallel one-track tubes, the new tunnel is rated to handle a whole lot more weight. It can handle trains up to 4,000 short tons​, more than twice that of its predecessor.

To dig the extremely long tunnel, miners used an army of mining machines three stories high and over 1,200 feet long, drilling from both sides. They finally met in the middle in 2010, and the last bit of track was laid down on October 31st of 2014.

How to Find ‘Strange Life’ on Alien Planets

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Detecting signs of life very different from that of Earth in the atmospheres of alien planets may be difficult, but it is possible, researchers say.

A team of scientists examined models of “super-Earths” — exoplanets slightly larger than Earth — to determine how easily signs of life could be spotted. They determined that such biosignatures could be identified more easily on planets orbiting stars producing relatively low amounts of radiation — but even then only if everything worked out just right.

The team, led by Sara Seager of the Massachusetts Institute of Technology (MIT), did not focus solely on Earth-like life.

“What we’ve been trying to do is move away from that,” William Bains, also of MIT, said during the Astrobiology Science Conference in Chicago in June. Bains worked with Seager and Renyu Hu to study super-Earths with hydrogen-rich atmospheres. “We wanted to build a model of biosignatures independent of Earth’s biology.”

‘A dynamic process’

Super-Earths are worlds up to 10 times more massive than our planet. Because of their size, they are more likely to retain an atmosphere rich in molecular hydrogen. The girth of super-Earths also makes them easier to discover, and their atmosphereseasier to characterize, relative to their Earth-size cousins. Hydrogen-rich super-Earths are now known to be quite commonthroughout the galaxy.

Bains and his colleagues simulated a planet 10 times as massive and nearly twice as wide as Earth, with an atmosphere rich in molecular hydrogen. Their simulations placed the planet in an orbit around three different types of stars: a sunlike star, a normal red dwarf (a star smaller and dimmer than the sun) and and an especially inactive red dwarf. (Different stellar types produce different levels of ultraviolet radiation, with the sunlike star producing the most, which affects how molecules break down in the atmosphere of orbiting planets.)

To search for biosignatures, Bains said, it’s important to understand why forms of life produce gas in the first place. Some gas is produced as a byproduct when energy is captured from the atmosphere. Other gases are byproducts of metabolic reactions, such as photosynthesis. The third type is created by life not as a result of its central chemical production but from stress, for signaling and in other functions.

“Life is a dynamic process,” Bains said.

The byproducts of life

After determining what gases could survive in the atmosphere, the scientists then calculated how much biomass would be needed to produce a detectable amount, and whether or not such an amount of life would be reasonable to find.

The team found four volatiles that would be generated by the production of energy in a hydrogen-rich atmosphere. Of them, three could be formed geologically, making them unreliable biosignatures.

“This was really disappointing,” Bains said.

The only interesting biosignature that the team came up in the first class was ammonia (NH3). For ammonia to be created, life would have to find a way to break the bonds between molecular nitrogen and molecular hydrogen. On Earth, synthetic chemistry can break each molecule apart individually, but no known system is capable of breaking both at once. Still, the team remains hopeful that a form of life could evolve on other worlds capable of capitalizing on the possibility.

Producing a detectable amount of ammonia in the atmosphere of a distant super-Earth would require a layer of life less than one bacterial cell thick, researchers said.

“Even if it was deader than the deadest place on Earth, we could detect it,” Bains said.

That’s the case for super-Earths orbiting sunlike stars, anyway. For alien planets receiving lower levels of ultraviolet radiation, such as those orbiting standard or quiet red dwarfs, the required biomass would need to be significantly higher.

While scientists should be able to detect ammonia in the atmosphere of distant planets, determining if it stems from life is another matter. At present, uncertainties about the size and mass of exoplanets remain high enough that worlds presently thought to be super-Earths could, in fact, be mini-Neptunes, gas giants smaller than those found in the solar system.

Disregarding the fact that surface conditions on gas planets would be essentially nonexistent, the deep atmospheres could produce ammonia without the aid of life. Determining whether a planet is a super-Earth or a mini-Neptune requires probing atmospheric pressures near the surface, something that even NASA’s upcoming James Webb Space Telescopewill be unable to accomplish, researchers said. [‪Building The James Webb Space Telescope (Photos)]

Even if scientists could conclusively identify a planet as rocky, it’s possible that the world could have collected ammonia during its evolution, as Saturn’s moon, Titan, did. Ices on the surface could break down with either internal heat or with the help of ultraviolet radiation, releasing ammonia into the atmosphere to create a false positive.

So, without getting up close to these distant worlds, characterizing whether ammonia in the atmosphere comes from life remains a significant challenge.

The research that formed the basis of Bains’ talk at the astrobiology conference was published in late 2013 in The Astrophysical Journal.

Seager, Bains and Hu also considered another group of gases — those produced for biomass building. Capturing energy from the environment requires energy. On Earth, a prime example is the oxygen plants release during the process of photosynthesis.

Unfortunately, the team was unable to identify any potentially useful biosignature gases of this type in a hydrogen-rich atmosphere. The gases that life might produce would be expected to exist naturally in the atmosphere of such a world, Bains said.

As a third option, the team examined molecules produced unrelated to energy generation. The presence of such gases would depend on the amount of ultraviolet (UV) radiation in the atmosphere, because high UV levels lead to the creation of lots of destructive hydrogen ions.

Planets orbiting sunlike stars, which emit lots of UV light, would therefore need an enormous density of biomass to produce biosignatures high enough to reach detectable levels. Even around a normal red dwarf, the values would need to be high, though they could be plausible when compared to Earth’s biomass surface density range.

According to the team, the James Webb Space Telescope (JWST) could spot evidence of biosignatures gas “if and only if every single factor is in our favor.”

Detecting life using JWST would require a pool of transiting planets around nearby red dwarfs. Because the stars are so dim, they would need to be relatively close to Earth in order for scientists to study their planets. These planets would need a molecular hydrogen atmosphere, which would be easier to study than a more Earth-like atmosphere. The star itself would need to be quiet, with little radiation. Finally, the planet itself must have life that produces a detectable gas as a biosignature.

“We will have the ability to predict some biosignatures gas independent of Earth,” Bains said. “But it’s going to be really hard to detect.”