Life signs could survive near surfaces of Enceladus and Europa

Europa, a moon of Jupiter, and Enceladus, a moon of Saturn, have evidence of oceans beneath their ice crusts. A NASA experiment suggests that if these oceans support life, signatures of that life in the form of organic molecules (e.g. amino acids, nucleic acids, etc.) could survive just under the surface ice despite the harsh radiation on these worlds. If robotic landers are sent to these moons to look for life signs, they would not have to dig very deep to find amino acids that have survived being altered or destroyed by radiation.

"Based on our experiments, the 'safe' sampling depth for amino acids on Europa is almost 8 inches (around 20 centimeters) at high latitudes of the trailing hemisphere (hemisphere opposite to the direction of Europa's motion around Jupiter) in the area where the surface hasn't been disturbed much by meteorite impacts," said Alexander Pavlov of NASA's Goddard Space Flight Center in Greenbelt, Maryland, lead author of a paper on the research published July 18 in Astrobiology. "Subsurface sampling is not required for the detection of amino acids on Enceladus -- these molecules will survive radiolysis (breakdown by radiation) at any location on the Enceladus surface less than a tenth of an inch (under a few millimeters) from the surface."

The frigid surfaces of these nearly airless moons are likely uninhabitable due to radiation from both high-speed particles trapped in their host planet's magnetic fields and powerful events in deep space, such as exploding stars. However, both have oceans under their icy surfaces that are heated by tides from the gravitational pull of the host planet and neighboring moons. These subsurface oceans could harbor life if they have other necessities, such as an energy supply as well as elements and compounds used in biological molecules.

The research team used amino acids in radiolysis experiments as possible representatives of biomolecules on icy moons. Amino acids can be created by life or by non-biological chemistry. However, finding certain kinds of amino acids on Europa or Enceladus would be a potential sign of life because they are used by terrestrial life as a component to build proteins. Proteins are essential to life as they are used to make enzymes which speed up or regulate chemical reactions and to make structures. Amino acids and other compounds from subsurface oceans could be brought to the surface by geyser activity or the slow churning motion of the ice crust.

To evaluate the survival of amino acids on these worlds, the team mixed samples of amino acids with ice chilled to about minus 321 Fahrenheit (-196 Celsius) in sealed, airless vials and bombarded them with gamma-rays, a type of high-energy light, at various doses. Since the oceans might host microscopic life, they also tested the survival of amino acids in dead bacteria in ice. Finally, they tested samples of amino acids in ice mixed with silicate dust to consider the potential mixing of material from meteorites or the interior with surface ice.

The experiments provided pivotal data to determine the rates at which amino acids break down, called radiolysis constants. With these, the team used the age of the ice surface and the radiation environment at Europa and Enceladus to calculate the drilling depth and locations where 10 percent of the amino acids would survive radiolytic destruction.

Although experiments to test the survival of amino acids in ice have been done before, this is the first to use lower radiation doses that don't completely break apart the amino acids, since just altering or degrading them is enough to make it impossible to determine if they are potential signs of life. This is also the first experiment using Europa/Enceladus conditions to evaluate the survival of these compounds in microorganisms and the first to test the survival of amino acids mixed with dust.

The team found that amino acids degraded faster when mixed with dust but slower when coming from microorganisms.

"Slow rates of amino acid destruction in biological samples under Europa and Enceladus-like surface conditions bolster the case for future life-detection measurements by Europa and Enceladus lander missions," said Pavlov. "Our results indicate that the rates of potential organic biomolecules' degradation in silica-rich regions on both Europa and Enceladus are higher than in pure ice and, thus, possible future missions to Europa and Enceladus should be cautious in sampling silica-rich locations on both icy moons."

A potential explanation for why amino acids survived longer in bacteria involves the ways ionizing radiation changes molecules -- directly by breaking their chemical bonds or indirectly by creating reactive compounds nearby which then alter or break down the molecule of interest. It's possible that bacterial cellular material protected amino acids from the reactive compounds produced by the radiation.

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Shedding light on comet Chury's unexpected chemical complexity

Comets are fossils from the ancient times and from the depths of our Solar System, and they are relics from the formation of the sun, planets, and moons. A team led by chemist Dr. Nora Hänni of the Physics Institute of the University of Bern, Department of Space Research and Planetary Sciences, has now succeeded for the first time in identifying a whole series of complex organic molecules at a comet as they report in a study published end of June in the   journal Nature Communications.

More precise analysis thanks to Bernese mass spectrometer

In the mid-1980ies, a fleet of spacecraft was sent out by the large space agencies to fly past Halley's comet. Onboard were several mass spectrometers that measured the chemical composition of both the comet's coma -- the thin atmosphere due to sublimation of cometary ices close to the Sun -, and also that of impacting dust particles. However, data collected by these instruments did not have the resolution needed to allow for unambiguous interpretation.

Now, more than 30 years later, the high-resolution mass spectrometer ROSINA, a Bern-led instrument onboard ESA's Rosetta spacecraft, collected data at comet 67P/Churyumov-Gerasimenko, also known as Chury, between 2014 and 2016. These data now allow the researchers to shed light for the first time on the complex organic budget of Chury.

The secret was hidden in the dust

When Chury reached its perihelion, the closest point to the Sun, it became very active. Sublimating cometary ices created outflow that dragged along dust particles. Expelled particles were heated up by solar irradiation to temperatures beyond those typically experienced at the cometary surface. This allows larger and heavier molecules to desorb, making them available to the high-resolution mass spectrometer ROSINA-DFMS (Rosetta Orbiter Sensor for Ion and Neutral Analysis-Double Focusing Mass Spectrometer). The astrophysicist Prof. em. Dr. Kathrin Altwegg, Principal Investigator of the ROSINA instrument and co-author of the new study, says: "Due to the extremely dusty conditions, the spacecraft had to retreat to a safe distance of a bit more than 200 km above the cometary surface in order for the instruments to be able to operate under steady conditions." Hence, it was possible to detect species composed of more than a handful of atoms which had previously remained hidden in the cometary dust.

The interpretation of such complex data is challenging. However, the Bernese team of researchers successfully identified a number of complex organic molecules, which have never been found in a comet before. "We found for instance naphthalene, which is responsible for the characteristic smell of mothballs. And we also found benzoic acid, a natural component of incense. In addition, we identified benzaldehyde, widely used to confer almond flavour to foods, and many other molecules." These heavy organics would apparently make Chury's scent even more complex, but also more appealing,  according to Hänni.

Apart from fragrant molecules, also many species with so-called prebiotic functionality have been identified in Chury's organics budget (e.g., formamide). Such compounds are important intermediates in the synthesis of biomolecules (e.g., sugars or amino acids). "It therefore seems likely that impacting comets -- as essential suppliers of organic material -- also contributed to the emergence of carbon-based life on Earth," explains Hänni.

Similar organics in Saturn and meteorites

In addition to the identification of individual molecules, the researchers also carried out a detailed characterization of the full ensemble of complex organic molecules in comet Chury, allowing to put it into the larger Solar System context. Parameters like the average sum formula of this organic material or the average bonding geometry of the carbon atoms in it are of importance for a broad scientific community, ranging from astronomers to Solar System scientists.

"It turned out that, on average, Chury's complex organics budget is identical to the soluble part of meteoritic organic matter," explains Hänni and adds: "Moreover, apart from the relative amount of hydrogen atoms, the molecular budget of Chury also strongly resembles the organic material raining down on Saturn from its innermost ring, as detected by the INMS mass spectrometer onboard NASA's Cassini spacecraft."

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Radioactive radiation could damage biological tissue also via a previously unnoticed mechanism

When cells are exposed to ionizing radiation, more destructive chain reactions may occur than previously thought. An international team led by researchers from the Max Planck Institute for Nuclear Physics in Heidelberg has for the first time observed intermolecular Coulombic decay in organic molecules. This is triggered by ionizing radiation such as from radioactivity or from space. The effect damages two neighbouring molecules and ultimately leads to the breaking of bonds -- like the ones in DNA and proteins. The finding not only improves the understanding of radiation damage but could also help in the search for more effective substances to support radiation therapy.

Sometimes radioactive damage cannot be great enough -- especially when it comes to destroying tumour tissue with ionizing radiation. In radiation therapy, substances that specifically enhance the damage of the radiation in the tumour tissue are used. "The intermolecular Coulombic decay we found could help make such sensitizers more effective," says Alexander Dorn, who heads a research group at the Max Planck Institute for Nuclear Physics and was instrumental in the current study. His team's observations could also improve our understanding of how artificial or natural ionizing radiation damages the genetic material of healthy tissue.

Excess energy leads to a Coulomb explosion

The DNA double helix of the genome resembles a rope ladder with rungs of nucleic base pairs. "Because experiments with the free nucleic bases are difficult, we initially studied pairs of benzene molecules as a model system," explains Dorn. These hydrocarbon rings are connected in a similar way to the nucleic bases stacked on top of each other in a strand of DNA. The researchers bombarded the benzene pairs with electrons, thereby imitating radioactive radiation to a certain extent. When an electron hit a benzene molecule, it was ionized and charged with a lot of energy. The team has now observed that the molecule transferred some of this energy to its partner molecule. This energy boost was enough to ionize the second molecule as well. Both molecules were thus positively charged. Of course, that didn't last long. The two molecular ions repelled each other and flew apart in a Coulomb explosion.

Until now, scientists had assumed that ionizing radiation damages biomolecules mainly indirectly. The high-energy radiation also ionizes the water of which a cell is largely composed and which surrounds biomolecules such as DNA. The ionized water molecules -- especially hydroxide ions -- then attack the DNA. And if an electron of the beta radiation or a gamma quantum does hit a DNA molecule directly, the excess energy normally is dissipated by processes in the molecule itself. It thus remains intact. Or at least that was the assumption up to now. In any case, the weak bonds between different molecules or different parts of the molecule -- as they exist in DNA and proteins -- should not be affected by this either. However, in their reaction microscope, the researchers observed that radioactive radiation can indeed break such bonds. This instrument allows them not only to detect the two separating benzene molecules and measure their energy but also to characterize the electrons emitted.

Fatal consequences of multiple DNA breaks

"It is not yet clear how the intermolecular Coulombic decay affects the DNA strand," says Dorn. If a single strand in the DNA ladder breaks, the consequences should not be too serious. However, the mechanism observed also releases several electrons that can "blow up" further pairs of molecules. And if both strands of DNA are broken in the immediate vicinity, this could have fatal consequences.

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Stellar cocoon with organic molecules at the edge of our galaxy

For the first time, astronomers have detected a newborn star and the surrounding cocoon of complex organic molecules at the edge of our Galaxy, which is known as the extreme outer Galaxy. The discovery, which revealed the hidden chemical complexity of our Universe, appears in a paper in The Astrophysical Journal.

The scientists from Niigata University (Japan), Academia Sinica Institute of Astronomy and Astrophysics (Taiwan), and the National Astronomical Observatory of Japan, used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to observe a newborn star (protostar) in the WB89-789 region, located in the extreme outer Galaxy. A variety of carbon-, oxygen-, nitrogen-, sulfur-, and silicon-bearing molecules, including complex organic molecules containing up to nine atoms, were detected. Such a protostar, as well as the associated cocoon of chemically-rich molecular gas, were for the first time detected at the edge of our Galaxy.

The ALMA observations reveal that various kinds of complex organic molecules, such as methanol (CH3OH), ethanol (C2H5OH), methyl formate (HCOOCH3), dimethyl ether (CH3OCH3), formamide (NH2CHO), propanenitrile (C2H5CN), etc., are present even in the primordial environment of the extreme outer Galaxy. Such complex organic molecules potentially act as the feedstock for larger prebiotic molecules.

Interestingly, the relative abundances of complex organic molecules in this newly discovered object resemble remarkably well what is found in similar objects in the inner Galaxy. The observations suggest that complex organic molecules are formed with similar efficiency even at the edge of our Galaxy, where the environment is very different from the solar neighborhood.

It is believed that the outer part of our Galaxy still harbors a primordial environment that existed in the early epoch of galaxy formation. The environmental characteristics of the extreme outer Galaxy, e.g., low abundance of heavy elements, small or no perturbation from Galactic spiral arms, are very different from those seen in the present-day solar neighborhood. Because of its unique characteristics, the extreme outer Galaxy is an excellent laboratory to study star formation and the interstellar medium in the past Galactic environment.

"With ALMA we were able to see a forming star and the surrounding molecular cocoon at the edge of our Galaxy," says Takashi Shimonishi, an astronomer at Niigata University, Japan, and the paper's lead author. "To our surprise, a variety of abundant complex organic molecules exists in the primordial environment of the extreme outer Galaxy. The interstellar conditions to form the chemical complexity might have persisted since the early history of the Universe," Shimonishi adds.

"These observations have revealed that complex organic molecules can be efficiently formed even in low-metallicity environments like the outermost regions of our Galaxy. This finding provides an important piece of the puzzle to understand how complex organic molecules are formed in the Universe," says Kenji Furuya, an astronomer at the National Astronomical Observatory of Japan, and the paper's co-author.

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Preconditions for life present 3.5 billion years ago

Microbial life already had the necessary conditions to exist on our planet 3.5 billion years ago. This was the conclusion reached by a research team after studying microscopic fluid inclusions in barium sulfate (barite) from the Dresser Mine in Marble Bar, Australia. In their publication "Ingredients for microbial life preserved in 3.5-billion-year-old fluid inclusions," the researchers suggest that organic carbon compounds which could serve as nutrients for microbial life already existed at this time. The study by first author Helge Mißbach (University of Göttingen, Germany) was published in the journal Nature Communications. Co-author Volker Lüders from the GFZ German Research Center for Geosciences carried out carbon isotope analyses on gases in fluid inclusions.

Fluid inclusions show potential for prehistoric life

Lüders assesses the results as surprising, although he cautions against misinterpreting them. "One should not take the study results as direct evidence for early life," says the GFZ researcher. Rather, the findings on the 3.5-billion-year-old fluids showed the existence of the potential for just such prehistoric life. Whether life actually arose from it at that time cannot be determined. Based on the results, "we now know a point in time from which we can say it would have been possible," explains Lüders.

Australian barites as geo-archives

Fluid inclusions in minerals are microscopic geo-archives for the migration of hot solutions and gases in the Earth's crust. Primary fluid inclusions were formed directly during mineral growth and provide important information about the conditions under which they were formed. This includes the pressure, temperature and the solution composition. In addition to an aqueous phase, fluid inclusions can also contain gases whose chemistry can persist for billions of years. The fluid inclusions examined in this study were trapped during crystallization of the host minerals. The fluid inclusions investigated in this study originate from the Dresser Mine in Australia. They were trapped during crystallisation of the host minerals of barium sulphate (barite). The research team analysed them extensively for their formation conditions, biosignatures and carbon isotopes.

In the course of the analyses, it turned out that they contained primordial metabolism -- and thus energy sources for life. The results of Lüders' carbon isotope analysis provided additional evidence for different carbon sources. While the gas-rich inclusions of gray barites contained traces of magmatic carbon, clear evidence of an organic origin of the carbon could be found in the fluid inclusions of black barites.

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Organic crystals' ice-forming superpowers

 At the heart of clouds are ice crystals. And at the heart of ice crystals, often, are aerosol particles -- dust in the atmosphere onto which ice can form more easily than in the open air.

It's a bit mysterious how this happens, though, because ice crystals are orderly structures of molecules, while aerosols are often disorganized chunks. New research by Valeria Molinero, distinguished professor of chemistry, and Atanu K. Metya, now at the Indian Institute of Technology Patna, shows how crystals of organic molecules, a common component of aerosols, can get the job done.

The story is more than that, though -- it's a throwback to Cold War-era cloud seeding research and an investigation into a peculiar memory effect that sees ice form more readily on these crystals the second time around.

The research, funded by the Air Force Office of Scientific Research, is published in the Journal of the American Chemical Society.

Throwback to cloud seeding

Molinero's research is focused on how ice forms, particularly the process of nucleation, which is the beginning of ice crystal formation. Under the right conditions, water molecules can nucleate ice on their own. But often some other material, called a nucleant, can help the process along.

After several studies on the ways that proteins can help form ice, Molinero and Metya turned their attention to organic ice nucleants (as used here, "organic" means organic compounds containing carbon) because they are similar to the ice-producing proteins and are found in airborne aerosols.

But a review of the scientific literature found that the papers discussing ice nucleation by organic compounds came from the 1950s and 1960s, with very little follow-up work after that until very recently.

"That made me really curious," Molinero says, "because there is a lot of interest now on organic aerosols and whether and how they promote the formation of ice in clouds, but all this new literature seemed dissociated from these early fundamental studies of organic ice nucleants."

Additional research revealed that the early work on organic ice nucleants was related to the study of cloud seeding, a post-war line of research into how particles (primarily silver iodide) could be introduced into the atmosphere to encourage cloud formation and precipitation. Scientists explored the properties of organic compounds as ice nucleants to see if they might be cost-effective alternatives to silver iodide.

But cloud seeding research collapsed in the 1970s after political pressures and fears of weather modification led to a ban on the practice in warfare. Funding and interest in organic ice nucleants dried up until recently, when climate research spurred a renewed interest in the chemistry of ice formation in the atmosphere.

"There has been a growing interest in ice nucleation by organic aerosols in the last few years, but no connection to these old studies on organic crystals," Molinero says. "So, I thought it was time to "rescue" them into the modern literature."

Going all classic

Phloroglucinol is one of the organic nucleants studied in the mid-20th century. It showed promise for controlling fog, but less for cloud seeding. Molinero and Metya revisited phloroglucinol as it proved potent at ice nucleation in the lab.

One question to answer is whether phloroglucinol nucleates ice through classical or non-classical processes. When ice nucleates on its own, without any surfaces or other molecules, the only hurdle to overcome is forming a stable crystallite of ice (only about 500 molecules in size under some conditions) that other molecules can build on to grow an ice crystal. That's classical nucleation.

Non-classical nucleation, involving a nucleant surface, occurs when a layer of water molecules assembles on the surface on which other water molecules can organize into a crystal lattice. The hurdle to overcome in non-classical nucleation is the formation of the monolayer.

Which applies to phloroglucinol? In the 1960s, researcher L.F. Evans concluded that it was non-classical. "I am still amazed he was able to deduce the existence of a monolayer and infer the mechanism was non-classical from experiments of freezing as a function of temperature alone!" Molinero says. But Molinero and Metya, using molecular simulations of how ice forms, found that it's more complicated.

"We find that the step that really decides whether water transforms to ice or not is not the formation of the monolayer but the growth of an ice crystallite on top," Molinero says. "That makes ice formation by organics classical although no less fascinating."

Holding on to memories of ice

The researchers also used their simulation methods to investigate an interesting memory effect previously observed with organic and other nucleants. When ice is formed, melted and formed again using these nucleants, the second round of crystallization is more effective than the first. It's assumed that the ice melts completely between crystallizations, and researchers have posed several potential explanations.

Molinero and Metya found that the memory effect isn't due to the ice changing the nucleant surface, nor to the monolayer of water persisting on the nucleant surface after melting. Instead, their simulations supported an explanation where crevices in the nucleant can hold on to small amounts of ice that melt at higher temperatures than the rest of the ice in the experiment. If these crevices are adjacent to one of the nucleant crystal surfaces that's good at forming ice, then it's off to the races when the second round of freezing begins.

Something in the air

Other mysteries still remain -- the mid-century studies of organic crystals found that at high pressures, around 1500 times atmospheric pressure, that the crystals are as efficient at organizing water molecules into ice as an ice crystal itself. Why? That's the focus of Molinero's next experiments.

More immediately, though, phloroglucinol is a naturally-occurring compound in the atmosphere, so anything that researchers can learn about it and other organic nucleants can help explain the ability of aerosols to nucleate ice and regulate the formation of clouds and precipitation.

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Key building block for organic molecules discovered in meteorites

 Scientists from Japan and the USA have confirmed the presence in meteorites of a key organic molecule which may have been used to build other organic molecules, including some used by life. The discovery validates theories of the formation of organic compounds in extraterrestrial environments.

The chemistry of life runs on organic compounds, molecules containing carbon and hydrogen, which also may include oxygen, nitrogen and other elements. While commonly associated with life, organic molecules also can be created by non-biological processes and are not necessarily indicators of life. An enduring mystery regarding the origin of life is how biology could have arisen from non-biological chemical processes, called prebiotic chemistry. Organic molecules from meteorites are one of the sources of organic compounds that lead to the formation of life on Earth.

Associate Professor Yasuhiro Oba from Hokkaido University led a team of researchers who discovered the presence of a prebiotic organic molecule called hexamethylenetetramine (HMT) in three different carbon-rich meteorites. Their discovery, published in the journal Nature Communications, validates models and theories that propose HMT as a key molecule in the formation of organic compounds in interstellar environments.

By confirming the presence of HMT in meteorites for the first time, this work supports the hypothesis that the compound was present in asteroids, the parent bodies of many meteorites. Early in the solar system's history, many asteroids could have been heated by collisions or the decay of radioactive elements. If some asteroids were warm enough and had liquid water, HMT could have broken down to provide building blocks that in turn reacted to make other important biological molecules which have been found in meteorites, including amino acids. Some types of amino acids are used by life to make proteins, which are used to build structures like hair and nails, or to speed up and regulate chemical reactions.

While the diversity of organic compounds in meteorites is well-documented, many questions remain about the processes by which these compounds were formed. The most important meteorites in this area of research are carbonaceous chondrites, stony meteorites that contain high percentages of water and organic compounds. Experimental models have shown that a combination of water, ammonia and methanol, when subjected to photochemical and thermal conditions common in extraterrestrial environments, give rise to a number or organic compounds, the most common of which is HMT. Interstellar ice is rich in methanol. Hypothetically, HMT should be common in water-containing extraterrestrial materials, but, until this study, it had not been detected.

HMT is susceptible to degradation when exposed to processes commonly used in the analysis of organic compounds in meteorites. The scientists developed a method that specifically extracted HMT from meteorites with minimal degradation. This method allowed them to isolate significant quantities of HMT and HMT derivatives from the meteorites Murchison, Murray and Tagish Lake.

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Prebiotic chemistry: In the beginning, there was sugar

 Organic molecules formed the basis for the evolution of life. But how could inorganic precursors have given rise to them? Ludwig-Maximilians-Universitaet (LMU) in Munich chemist Oliver Trapp now reports a reaction pathway in which minerals catalyze the formation of sugars in the absence of water.

More than 4 billion years ago, the Earth was very far from being the Blue Planet it would later become. At that point it had just begun to cool and, in the course of that process, the concentric structural zones that lie ever deeper beneath our feet were formed. The early Earth was dominated by volcanism, and the atmosphere was made up of carbon dioxide, nitrogen, methane, ammonia, hydrogen sulfide and water vapor. In this decidedly inhospitable environment the building blocks of life were formed. How then might this have come about?

Researchers have puzzled over the question for decades. The first breakthrough was made in 1953 by two chemists, named Stanley Miller and Harold C. Urey, at the University of Chicago. In their experiments, they simulated the atmosphere of the primordial Earth in a closed reaction system that contained the gases mentioned above. A miniature 'ocean' was heated to provide water vapor, and electrical discharges were passed through the system to mimic the effects of lightning. When they analyzed the chemicals produced under these conditions, Miller and Urey detected amino acids -- the basic constituents of proteins -- as well as a number of other organic acids.

It is now known that the conditions employed in these experiments did not reflect those that prevailed on the early Earth. Nevertheless, the Miller-Urey experiment initiated the field of prebiotic chemical evolution. However, it not throw much light on how other classes of molecules found in all biological cells -- such as sugars, fats and nucleic acids -- might have been generated. These compounds are however indispensable ingredients of the process that led to the first bacteria and subsequently to photosynthetic cyanobacteria that produced oxygen. This is why Oliver Trapp, Professor of Organic Chemistry at LMU, decided to focus his research on the prebiotic synthesis of these substances.

From formaldehyde to sugar

The story of synthetic routes from smaller precursors to sugars goes back almost a century prior to the Miller-Urey experiment. In 1861, the Russian chemist Alexander Butlerov showed that formaldehyde could give rise to various sugars via what became known as the formose reaction. Miller und Urey in fact found formic acid in their experiments, and it can be readily reduced to yield formaldehyde. Butlerov also discovered that the formose reaction is promoted by a number of metal oxides and hydroxides, including those of calcium, barium, thallium and lead. Notably calcium is abundantly available on and below the Earth's surface.

However, the hypothesis that sugars could have been produced via the formose reaction runs into two difficulties. The 'classical' formose reaction produces a diverse mixture of compounds, and it takes place only in aqueous media. These requirements are at odds with the fact that sugars have been detected in meteorites.

Together with colleagues at LMU and the Max Planck Institute for Astronomy in Heidelberg, Trapp therefore decided to explore whether formaldehyde could give rise to sugars in a solid-phase system. With a view to simulating the kinds of mechanical forces to which solid minerals would have been subjected, all the reaction components were combined in a ball mill -- in the absence of solvents, but adding enough formaldehyde to saturate the powdered solids

And indeed, the formose reaction was observed and several different minerals were found to catalyze it. The formaldehyde was adsorbed onto the solid particles, and the interaction resulted in the formation of the formaldehyde dimer (glycolaldehyde) -- and ribose, the 5-carbon sugar that is an essential constituent of ribonucleic acid (RNA). RNA is thought to have merged prior to DNA, and it serves as the repository of genetic information in many viruses, as well as providing the templates for protein synthesis in all cellular organisms. More complex sugars were also obtained in the experiments, together with a few byproducts, such as lactic acid and methanol.

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Tracing the cosmic origin of complex organic molecules with their radiofrequency footprint

 The origin of life on Earth is a topic that has piqued human curiosity since probably before recorded history began. But how did the organic matter that constitutes lifeforms even arrive at our planet? Though this is still a subject of debate among scholars and practitioners in related fields, one approach to answering this question involves finding and studying complex organic molecules (COMs) in outer space.

Many scientists have reported finding all sorts of COMs in molecular clouds -- gigantic regions of interstellar space that contain various types of gases. This is generally done using radio telescopes, which measure and record radiofrequency waves to provide a frequency profile of the incoming radiation called spectrum. Molecules in space are usually rotating in various directions, and they emit or absorb radio waves at very specific frequencies when their rotational speed changes. Current physics and chemistry models allow us to approximate the composition of what a radio telescope is pointed at, via analysis of the intensity of the incoming radiation at these frequencies.

In a recent study published in Monthly Notices of the Royal Astronomical Society, Dr Mitsunori Araki from Tokyo University of Science, along with other scientists from across Japan, tackled a difficult question in the search for interstellar COMs: how can we assert the presence of COMs in the less dense regions of molecular clouds? Because molecules in space are mostly energized by collisions with hydrogen molecules, COMs in the low-density regions of molecular clouds emit less radio waves, making it difficult for us to detect them. However, Dr Araki and his team took a different approach based on a special organic molecule called acetonitrile (CH3CN).

Acetonitrile is an elongated molecule that has two independent ways of rotating: around its long axis, like a spinning top, or as if it were a pencil spinning around your thumb. The latter type of rotation tends to spontaneously slow down due to the emission of radio waves and, in the low-density regions of molecular clouds, it naturally becomes less energetic or "cold."

In contrast, the other type of rotation does not emit radiation and therefore remains active without slowing down. This particular behavior of the acetonitrile molecule was the basis on which Dr Araki and his team managed to detect it. He explains: "In low-density regions of molecular clouds, the proportion of acetonitrile molecules rotating like a spinning top should be higher. Thus, it can be inferred that an extreme state in which a lot of them would be rotating in this way should exist. Our research team was, however, the first to predict its existence, select astronomical bodies that could be observed, and actually begin exploration."

Instead of going for radio wave emissions, they focused on radio wave absorption. The "cold" state of the low-density region, if populated by acetonitrile molecules, should have a predictable effect on the radiation that originates in celestial bodies like stars and goes through it. In other words, the spectrum of a radiating body that we perceive on Earth as being "behind" a low-density region would be filtered by acetonitrile molecules spinning like a top in a calculable way, before it reaches our telescope on earth. Therefore, Dr Araki and his team had to carefully select radiating bodies that could be used as an appropriate "background light" to see if the shadow of "cold" acetonitrile appeared in the measured spectrum. To this end, they used the 45 m radio telescope of the Nobeyama Radio Observatory, Japan, to explore this effect in a low-density region around the "Sagittarius molecular cloud Sgr B2(M)," one of the largest molecular clouds in the vicinity of the center of our galaxy.

After careful analysis of the spectra measured, the scientists concluded that the region analyzed was rich in acetonitrile molecules rotating like a spinning top; the proportion of molecules rotating this way was actually the highest ever recorded. Excited about the results, Dr Araki remarks: "By considering the special behavior of acetonitrile, its amount in the low-density region around Sgr B2(M) can be accurately determined. Because acetonitrile is a representative COM in space, knowing its amount and distribution though space can help us probe further into the overall distribution of organic matter."

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