Latest news with #Miller-Urey
Time of India
25-04-2025
- Science
- Time of India
Scientists claim to have found evidence of alien life. But 'biosignatures' might hide more than they reveal
Representative Image (TOI) SYDNEY: Whether or not we're alone in the universe is one of the biggest questions in science. A recent study, led by astrophysicist Nikku Madhusudhan at the University of Cambridge, suggests the answer might be no. Based on observations from NASA's James Webb Space Telescope , the study points to alien life on K2-18b, a distant exoplanet 124 light years from Earth . The researchers found strong evidence of a chemical called dimethyl sulfide (DMS) in the planet's atmosphere. On Earth, DMS is produced only by living organisms, so it appears to be a compelling sign of life, or "biosignature". While the new findings have made headlines, a look at the history of astrobiology shows similar discoveries have been inconclusive in the past. The issue is partly theoretical: scientists and philosophers still have no agreed-upon definition of exactly what life is. Unlike the older Hubble telescope, which orbited Earth, NASA's James Webb Space Telescope is placed in orbit around the Sun. This gives it a better view of objects in deep space. When distant exoplanets pass in front of their host star, astronomers can deduce what chemicals are in their atmospheres from the tell-tale wavelengths they leave in the detected light. Since the precision of these readings can vary, scientists estimate a margin of error for their results, to rule out random chance. The recent study of K2-18b found only a 0.3 per cent probability that the readings were a fluke, leaving researchers confident in their detection of DMS. On Earth, DMS is only produced by life, mostly aquatic phytoplankton. This makes it a persuasive biosignature. The findings line up with what scientists already conjecture about K2-18b. Considered a "Hycean" world (a portmanteau of "hydrogen" and "ocean"), K2-18b is thought to feature a hydrogen-rich atmosphere and a surface covered with liquid water. These conditions are favourable to life. So does this mean K2-18b's oceans are crawling with extraterrestrial microbes? Some experts are less certain. Speaking to the New York Times, planetary scientist Christopher Glein expressed doubt that the study represents a "smoking gun". And past experiences teach us that in astrobiology, inconclusive findings are the norm. Astrobiology has its origins in efforts to explain how life began on our own planet. In the early 1950s, the Miller-Urey experiment showed that an electrical current could produce organic compounds from a best-guess reconstruction of the chemistry in Earth's earliest oceans, sometimes called the "primordial soup". Although it gave no real indication of how life in fact first evolved, the experiment left astrobiology with a framework for investigating the chemistry of alien worlds. In 1975, the first Mars landers, Viking 1 and 2, conducted experiments with collected samples of Martian soil. In one experiment, nutrients added to soil samples appeared to produce carbon dioxide, suggesting microbes were digesting the nutrients. Initial excitement quickly dissipated, as other tests failed to pick up organic compounds in the soil. And later studies identified plausible non-biological explanations for the carbon dioxide. One explanation points to a mineral abundant on Mars called perchlorate. Interactions between perchlorate and cosmic rays may have led to chemical reactions similar to those observed by the Viking tests. Concerns the landers' instruments had been contaminated on Earth also introduced uncertainty. In 1996, a NASA team announced a Martian meteorite discovered in Antarctica bore signs of past alien life. Specimen ALH84001 showed evidence of organic hydrocarbons, as well as magnetite crystals arranged in a distinctive pattern only produced biologically on Earth. More suggestive were the small, round structures in the rock resembling fossilised bacteria. Again, closer analysis led to disappointment. Non-biological explanations were found for the magnetite grains and hydrocarbons, while the fossil bacteria were deemed too small to plausibly support life. The most recent comparable discovery - claims of phosphine gas on Venus in 2020 - is also still controversial. Phosphine is considered a biosignature, since on Earth it's produced by bacterial life in low-oxygen environments, particularly in the digestive tracts of animals. Some astronomers claim the detected phosphine signal is too weak, or attributable to inorganically produced sulfur compounds. Each time biosignatures are found, biologists confront the ambiguous distinction between life and non-life, and the difficulty of extrapolating characteristics of life on Earth to alien environments. Carol Cleland, a leading philosopher of science, has called this the problem of finding "life as we don't know it". We still know very little about how life first emerged on Earth. This makes it hard to know what to expect from the primitive lifeforms that might exist on Mars or K2-18b. It's uncertain whether such lifeforms would resemble Earth life at all. Alien life might manifest in surprising and unrecognisable ways: while life on Earth is carbon-based, cellular, and reliant on self-replicating molecules such as DNA, an alien lifeform might fulfil the same functions with totally unfamiliar materials and structures. Our knowledge of the environmental conditions on K2-18b is also limited, so it's hard to imagine the adaptations a Hycean organism might need to survive there. Chemical biosignatures derived from life on Earth, it seems, might be a misleading guide. Philosophers of biology argue that a general definition of life will need to go beyond chemistry. According to one view, life is defined by its organisation, not the list of chemicals making it up: living things embody a kind of self-organisation able to autonomously produce its own parts, sustain a metabolism, and maintain a boundary or membrane separating inside from outside. Some philosophers of science claim such a definition is too imprecise. In my own research, I've argued that this kind of generality is a strength: it helps keep our theories flexible, and applicable to new contexts. K2-18b may be a promising candidate for identifying extraterrestrial life. But excitement about biosignatures such as DMS disguises deeper, theoretical problems that also need to be resolved. Novel lifeforms in distant, unfamiliar environments might not be detectable in the ways we expect. Philosophers and scientists will have to work together on non-reductive descriptions of living processes, so that when we do stumble across alien life, we don't miss it.
The Independent
23-04-2025
- Science
- The Independent
Scientists say they've found evidence of alien life. The truth is more complicated
Whether or not we're alone in the universe is one of the biggest questions in science. A recent study, led by astrophysicist Nikku Madhusudhan at the University of Cambridge, suggests the answer might be no. Based on observations from Nasa 's James Webb Space Telescope, the study points to alien life on K2-18b, a distant exoplanet 124 light years from Earth. The researchers found strong evidence of a chemical called dimethyl sulfide (DMS) in the planet's atmosphere. On Earth, DMS is produced only by living organisms, so it appears to be a compelling sign of life, or 'biosignature'. While the new findings have made headlines, a look at the history of astrobiology shows similar discoveries have been inconclusive in the past. The issue is partly theoretical: scientists and philosophers still have no agreed-upon definition of exactly what life is. A closer look Unlike the older Hubble telescope, which orbited Earth, Nasa's James Webb Space Telescope is placed in orbit around the Sun. This gives it a better view of objects in deep space. When distant exoplanets pass in front of their host star, astronomers can deduce what chemicals are in their atmospheres from the tell-tale wavelengths they leave in the detected light. Since the precision of these readings can vary, scientists estimate a margin of error for their results, to rule out random chance. The recent study of K2-18b found only a 0.3% probability that the readings were a fluke, leaving researchers confident in their detection of DMS. On Earth, DMS is only produced by life, mostly aquatic phytoplankton. This makes it a persuasive biosignature. The findings line up with what scientists already conjecture about K2-18b. Considered a 'Hycean' world (a portmanteau of 'hydrogen' and 'ocean'), K2-18b is thought to feature a hydrogen-rich atmosphere and a surface covered with liquid water. These conditions are favourable to life. So does this mean K2-18b's oceans are crawling with extraterrestrial microbes? Some experts are less certain. Speaking to the New York Times, planetary scientist Christopher Glein expressed doubt that the study represents a 'smoking gun'. And past experiences teach us that in astrobiology, inconclusive findings are the norm. Life as we don't know it Astrobiology has its origins in efforts to explain how life began on our own planet. In the early 1950s, the Miller-Urey experiment showed that an electrical current could produce organic compounds from a best-guess reconstruction of the chemistry in Earth's earliest oceans – sometimes called the 'primordial soup'. Although it gave no real indication of how life in fact first evolved, the experiment left astrobiology with a framework for investigating the chemistry of alien worlds. In 1975, the first Mars landers – Viking 1 and 2 – conducted experiments with collected samples of Martian soil. In one experiment, nutrients added to soil samples appeared to produce carbon dioxide, suggesting microbes were digesting the nutrients. Initial excitement quickly dissipated, as other tests failed to pick up organic compounds in the soil. And later studies identified plausible non-biological explanations for the carbon dioxide. One explanation points to a mineral abundant on Mars called perchlorate. Interactions between perchlorate and cosmic rays may have led to chemical reactions similar to those observed by the Viking tests. Concerns the landers' instruments had been contaminated on Earth also introduced uncertainty. In 1996, a Nasa team announced a Martian meteorite discovered in Antarctica bore signs of past alien life. Specimen ALH84001 showed evidence of organic hydrocarbons, as well as magnetite crystals arranged in a distinctive pattern only produced biologically on Earth. More suggestive were the small, round structures in the rock resembling fossilised bacteria. Again, closer analysis led to disappointment. Non-biological explanations were found for the magnetite grains and hydrocarbons, while the fossil bacteria were deemed too small to plausibly support life. The most recent comparable discovery – claims of phosphine gas on Venus in 2020 – is also still controversial. Phosphine is considered a biosignature, since on Earth it's produced by bacterial life in low-oxygen environments, particularly in the digestive tracts of animals. Some astronomers claim the detected phosphine signal is too weak, or attributable to inorganically produced sulfur compounds. Each time biosignatures are found, biologists confront the ambiguous distinction between life and non-life, and the difficulty of extrapolating characteristics of life on Earth to alien environments. Carol Cleland, a leading philosopher of science, has called this the problem of finding 'life as we don't know it'. Moving beyond chemistry We still know very little about how life first emerged on Earth. This makes it hard to know what to expect from the primitive lifeforms that might exist on Mars or K2-18b. It's uncertain whether such lifeforms would resemble Earth life at all. Alien life might manifest in surprising and unrecognisable ways: while life on Earth is carbon-based, cellular, and reliant on self-replicating molecules such as DNA, an alien lifeform might fulfil the same functions with totally unfamiliar materials and structures. Our knowledge of the environmental conditions on K2-18b is also limited, so it's hard to imagine the adaptations a Hycean organism might need to survive there. Chemical biosignatures derived from life on Earth, it seems, might be a misleading guide. Philosophers of biology argue that a general definition of life will need to go beyond chemistry. According to one view, life is defined by its organisation, not the list of chemicals making it up: living things embody a kind of self-organisation able to autonomously produce its own parts, sustain a metabolism, and maintain a boundary or membrane separating inside from outside. Some philosophers of science claim such a definition is too imprecise. In my own research, I've argued that this kind of generality is a strength: it helps keep our theories flexible, and applicable to new contexts. K2-18b may be a promising candidate for identifying extraterrestrial life. But excitement about biosignatures such as DMS disguises deeper, theoretical problems that also need to be resolved. Novel lifeforms in distant, unfamiliar environments might not be detectable in the ways we expect. Philosophers and scientists will have to work together on non-reductive descriptions of living processes, so that when we do stumble across alien life, we don't miss it.
CNN
28-03-2025
- Science
- CNN
Scientists redid an experiment that showed how life on Earth could have started. They found a new possibility
Summary Scientists suggest microlightning in water droplets could have sparked the creation of Earth's earliest organic molecules. The new research, published in Science Advances, builds upon the landmark 1953 Miller-Urey experiment. Electrical exchanges between oppositely charged water droplets can result in the production of amino acids, the researchers found. This process could have been more frequent than lightning on ancient Earth, creating abundant building blocks for life. Alternative theories on life's origins suggest organic molecules originated at hydrothermal vents or arrived from space via asteroids. 'It's alive! IT'S ALIVE!' In the 1931 movie 'Frankenstein,' Dr. Henry Frankenstein howling his triumph was an electrifying moment in more ways than one. As massive bolts of lightning and energy crackled, Frankenstein's monster stirred on a laboratory table, its corpse brought to life by the power of electricity. Electrical energy may also have sparked the beginnings of life on Earth billions of years ago, though with a bit less scenery-chewing than that classic film scene. Earth is around 4.5 billion years old, and the oldest direct fossil evidence of ancient life — stromatolites, or microscopic organisms preserved in layers known as microbial mats — is about 3.5 billion years old. However, some scientists suspect life originated even earlier, emerging from accumulated organic molecules in primitive bodies of water, a mixture sometimes referred to as primordial soup. But where did that organic material come from in the first place? Researchers decades ago proposed that lightning caused chemical reactions in ancient Earth's oceans and spontaneously produced the organic molecules. Now, new research published March 14 in the journal Science Advances suggests that fizzes of barely visible 'microlightning,' generated between charged droplets of water mist, could have been potent enough to cook up amino acids from inorganic material. Amino acids — organic molecules that combine to form proteins — are life's most basic building blocks and would have been the first step toward the evolution of life. 'It's recognized that an energetic catalyst was almost certainly required to facilitate some of the reactions on early Earth that led to the origin of life,' said astrobiologist and geobiologist Dr. Amy J. Williams, an associate professor in the department of geosciences at the University of Florida. For animo acids to form, they need nitrogen atoms that can bond with carbon. Freeing up atoms from nitrogen gas requires severing powerful molecular bonds and takes an enormous amount of energy, according to Williams, who was not involved in the research. 'Lightning, or in this case, microlightning, has the energy to break molecular bonds and therefore facilitate the generation of new molecules that are critical to the origin of life on Earth,' Williams told CNN in an email. To recreate a scenario that may have produced Earth's first organic molecules, researchers built upon experiments from 1953 when American chemists Stanley Miller and Harold Urey concocted a gas mixture mimicking the atmosphere of ancient Earth. Miller and Urey combined ammonia (NH3), methane (CH4), hydrogen (H2) and water, enclosed their 'atmosphere' inside a glass sphere and jolted it with electricity, producing simple amino acids containing carbon and nitrogen. The Miller-Urey experiment, as it is now known, supported the scientific theory of abiogenesis: that life could emerge from nonliving molecules. For the new study, scientists revisited the 1953 experiments but directed their attention toward electrical activity on a smaller scale, said senior study author Dr. Richard Zare, the Marguerite Blake Wilbur Professor of Natural Science and professor of chemistry at Stanford University in California. Zare and his colleagues looked at electricity exchange between charged water droplets measuring between 1 micron and 20 microns in diameter. (The width of a human hair is 100 microns.) 'The big droplets are positively charged. The little droplets are negatively charged,' Zare told CNN. 'When droplets that have opposite charges are close together, electrons can jump from the negatively charged droplet to the positively charged droplet.' The researchers mixed ammonia, carbon dioxide, methane and nitrogen in a glass bulb, then sprayed the gases with water mist, using a high-speed camera to capture faint flashes of microlightning in the vapor. When they examined the bulb's contents, they found organic molecules with carbon-nitrogen bonds. These included the amino acid glycine and uracil, a nucleotide base in RNA. 'We discovered no new chemistry; we have actually reproduced all the chemistry that Miller and Urey did in 1953,' Zare said. Nor did the team discover new physics, he added — the experiments were based on known principles of electrostatics. 'What we have done, for the first time, is we have seen that little droplets, when they're formed from water, actually emit light and get this spark,' Zare said. 'That's new. And that spark causes all types of chemical transformations.' Lightning is a dramatic display of electrical power, but it is also sporadic and unpredictable. Even on a volatile Earth billions of years ago, lightning may have been too infrequent to produce amino acids in quantities sufficient for life — a fact that has cast doubt on such theories in the past, Zare said. Water spray, however, would have been more common than lightning. A more likely scenario is that mist-generated microlightning constantly zapped amino acids into existence from pools and puddles, where the molecules could accumulate and form more complex molecules, eventually leading to the evolution of life. 'Microdischarges between obviously charged water microdroplets make all the organic molecules observed previously in the Miller-Urey experiment,' Zare said. 'We propose that this is a new mechanism for the prebiotic synthesis of molecules that constitute the building blocks of life.' However, even with the new findings about microlightning, questions remain about life's origins, he added. While some scientists support the notion of electrically charged beginnings for life's earliest building blocks, an alternative abiogenesis hypothesis proposes that Earth's first amino acids were cooked up around hydrothermal vents on the seafloor, produced by a combination of seawater, hydrogen-rich fluids and extreme pressure. Yet another hypothesis suggests that organic molecules didn't originate on Earth at all. Rather, they formed in space and were carried here by comets or fragments of asteroids, a process known as panspermia. 'We still don't know the answer to this question,' Zare said. 'But I think we're closer to understanding something more about what could have happened.' Though the details of life's origins on Earth may never be fully explained, 'this study provides another avenue for the formation of molecules crucial to the origin of life,' Williams said. 'Water is a ubiquitous aspect of our world, giving rise to the moniker 'Blue Marble' to describe the Earth from space. Perhaps the falling of water, the most crucial element that sustains us, also played a greater role in the origin of life on Earth than we previously recognized.'
CNN
28-03-2025
- Science
- CNN
Scientists redid an experiment that showed how life on Earth could have started. They found a new possibility
Summary Scientists suggest microlightning in water droplets could have sparked the creation of Earth's earliest organic molecules. The new research, published in Science Advances, builds upon the landmark 1953 Miller-Urey experiment. Electrical exchanges between oppositely charged water droplets can result in the production of amino acids, the researchers found. This process could have been more frequent than lightning on ancient Earth, creating abundant building blocks for life. Alternative theories on life's origins suggest organic molecules originated at hydrothermal vents or arrived from space via asteroids. 'It's alive! IT'S ALIVE!' In the 1931 movie 'Frankenstein,' Dr. Henry Frankenstein howling his triumph was an electrifying moment in more ways than one. As massive bolts of lightning and energy crackled, Frankenstein's monster stirred on a laboratory table, its corpse brought to life by the power of electricity. Electrical energy may also have sparked the beginnings of life on Earth billions of years ago, though with a bit less scenery-chewing than that classic film scene. Earth is around 4.5 billion years old, and the oldest direct fossil evidence of ancient life — stromatolites, or microscopic organisms preserved in layers known as microbial mats — is about 3.5 billion years old. However, some scientists suspect life originated even earlier, emerging from accumulated organic molecules in primitive bodies of water, a mixture sometimes referred to as primordial soup. But where did that organic material come from in the first place? Researchers decades ago proposed that lightning caused chemical reactions in ancient Earth's oceans and spontaneously produced the organic molecules. Now, new research published March 14 in the journal Science Advances suggests that fizzes of barely visible 'microlightning,' generated between charged droplets of water mist, could have been potent enough to cook up amino acids from inorganic material. Amino acids — organic molecules that combine to form proteins — are life's most basic building blocks and would have been the first step toward the evolution of life. 'It's recognized that an energetic catalyst was almost certainly required to facilitate some of the reactions on early Earth that led to the origin of life,' said astrobiologist and geobiologist Dr. Amy J. Williams, an associate professor in the department of geosciences at the University of Florida. For animo acids to form, they need nitrogen atoms that can bond with carbon. Freeing up atoms from nitrogen gas requires severing powerful molecular bonds and takes an enormous amount of energy, according to Williams, who was not involved in the research. 'Lightning, or in this case, microlightning, has the energy to break molecular bonds and therefore facilitate the generation of new molecules that are critical to the origin of life on Earth,' Williams told CNN in an email. To recreate a scenario that may have produced Earth's first organic molecules, researchers built upon experiments from 1953 when American chemists Stanley Miller and Harold Urey concocted a gas mixture mimicking the atmosphere of ancient Earth. Miller and Urey combined ammonia (NH3), methane (CH4), hydrogen (H2) and water, enclosed their 'atmosphere' inside a glass sphere and jolted it with electricity, producing simple amino acids containing carbon and nitrogen. The Miller-Urey experiment, as it is now known, supported the scientific theory of abiogenesis: that life could emerge from nonliving molecules. For the new study, scientists revisited the 1953 experiments but directed their attention toward electrical activity on a smaller scale, said senior study author Dr. Richard Zare, the Marguerite Blake Wilbur Professor of Natural Science and professor of chemistry at Stanford University in California. Zare and his colleagues looked at electricity exchange between charged water droplets measuring between 1 micron and 20 microns in diameter. (The width of a human hair is 100 microns.) 'The big droplets are positively charged. The little droplets are negatively charged,' Zare told CNN. 'When droplets that have opposite charges are close together, electrons can jump from the negatively charged droplet to the positively charged droplet.' The researchers mixed ammonia, carbon dioxide, methane and nitrogen in a glass bulb, then sprayed the gases with water mist, using a high-speed camera to capture faint flashes of microlightning in the vapor. When they examined the bulb's contents, they found organic molecules with carbon-nitrogen bonds. These included the amino acid glycine and uracil, a nucleotide base in RNA. 'We discovered no new chemistry; we have actually reproduced all the chemistry that Miller and Urey did in 1953,' Zare said. Nor did the team discover new physics, he added — the experiments were based on known principles of electrostatics. 'What we have done, for the first time, is we have seen that little droplets, when they're formed from water, actually emit light and get this spark,' Zare said. 'That's new. And that spark causes all types of chemical transformations.' Lightning is a dramatic display of electrical power, but it is also sporadic and unpredictable. Even on a volatile Earth billions of years ago, lightning may have been too infrequent to produce amino acids in quantities sufficient for life — a fact that has cast doubt on such theories in the past, Zare said. Water spray, however, would have been more common than lightning. A more likely scenario is that mist-generated microlightning constantly zapped amino acids into existence from pools and puddles, where the molecules could accumulate and form more complex molecules, eventually leading to the evolution of life. 'Microdischarges between obviously charged water microdroplets make all the organic molecules observed previously in the Miller-Urey experiment,' Zare said. 'We propose that this is a new mechanism for the prebiotic synthesis of molecules that constitute the building blocks of life.' However, even with the new findings about microlightning, questions remain about life's origins, he added. While some scientists support the notion of electrically charged beginnings for life's earliest building blocks, an alternative abiogenesis hypothesis proposes that Earth's first amino acids were cooked up around hydrothermal vents on the seafloor, produced by a combination of seawater, hydrogen-rich fluids and extreme pressure. Yet another hypothesis suggests that organic molecules didn't originate on Earth at all. Rather, they formed in space and were carried here by comets or fragments of asteroids, a process known as panspermia. 'We still don't know the answer to this question,' Zare said. 'But I think we're closer to understanding something more about what could have happened.' Though the details of life's origins on Earth may never be fully explained, 'this study provides another avenue for the formation of molecules crucial to the origin of life,' Williams said. 'Water is a ubiquitous aspect of our world, giving rise to the moniker 'Blue Marble' to describe the Earth from space. Perhaps the falling of water, the most crucial element that sustains us, also played a greater role in the origin of life on Earth than we previously recognized.'
CNN
28-03-2025
- Science
- CNN
Scientists redid an experiment that showed how life on Earth could have started. They found a new possibility
Summary Scientists suggest microlightning in water droplets could have sparked the creation of Earth's earliest organic molecules. The new research, published in Science Advances, builds upon the landmark 1953 Miller-Urey experiment. Electrical exchanges between oppositely charged water droplets can result in the production of amino acids, the researchers found. This process could have been more frequent than lightning on ancient Earth, creating abundant building blocks for life. Alternative theories on life's origins suggest organic molecules originated at hydrothermal vents or arrived from space via asteroids. 'It's alive! IT'S ALIVE!' In the 1931 movie 'Frankenstein,' Dr. Henry Frankenstein howling his triumph was an electrifying moment in more ways than one. As massive bolts of lightning and energy crackled, Frankenstein's monster stirred on a laboratory table, its corpse brought to life by the power of electricity. Electrical energy may also have sparked the beginnings of life on Earth billions of years ago, though with a bit less scenery-chewing than that classic film scene. Earth is around 4.5 billion years old, and the oldest direct fossil evidence of ancient life — stromatolites, or microscopic organisms preserved in layers known as microbial mats — is about 3.5 billion years old. However, some scientists suspect life originated even earlier, emerging from accumulated organic molecules in primitive bodies of water, a mixture sometimes referred to as primordial soup. But where did that organic material come from in the first place? Researchers decades ago proposed that lightning caused chemical reactions in ancient Earth's oceans and spontaneously produced the organic molecules. Now, new research published March 14 in the journal Science Advances suggests that fizzes of barely visible 'microlightning,' generated between charged droplets of water mist, could have been potent enough to cook up amino acids from inorganic material. Amino acids — organic molecules that combine to form proteins — are life's most basic building blocks and would have been the first step toward the evolution of life. 'It's recognized that an energetic catalyst was almost certainly required to facilitate some of the reactions on early Earth that led to the origin of life,' said astrobiologist and geobiologist Dr. Amy J. Williams, an associate professor in the department of geosciences at the University of Florida. For animo acids to form, they need nitrogen atoms that can bond with carbon. Freeing up atoms from nitrogen gas requires severing powerful molecular bonds and takes an enormous amount of energy, according to Williams, who was not involved in the research. 'Lightning, or in this case, microlightning, has the energy to break molecular bonds and therefore facilitate the generation of new molecules that are critical to the origin of life on Earth,' Williams told CNN in an email. To recreate a scenario that may have produced Earth's first organic molecules, researchers built upon experiments from 1953 when American chemists Stanley Miller and Harold Urey concocted a gas mixture mimicking the atmosphere of ancient Earth. Miller and Urey combined ammonia (NH3), methane (CH4), hydrogen (H2) and water, enclosed their 'atmosphere' inside a glass sphere and jolted it with electricity, producing simple amino acids containing carbon and nitrogen. The Miller-Urey experiment, as it is now known, supported the scientific theory of abiogenesis: that life could emerge from nonliving molecules. For the new study, scientists revisited the 1953 experiments but directed their attention toward electrical activity on a smaller scale, said senior study author Dr. Richard Zare, the Marguerite Blake Wilbur Professor of Natural Science and professor of chemistry at Stanford University in California. Zare and his colleagues looked at electricity exchange between charged water droplets measuring between 1 micron and 20 microns in diameter. (The width of a human hair is 100 microns.) 'The big droplets are positively charged. The little droplets are negatively charged,' Zare told CNN. 'When droplets that have opposite charges are close together, electrons can jump from the negatively charged droplet to the positively charged droplet.' The researchers mixed ammonia, carbon dioxide, methane and nitrogen in a glass bulb, then sprayed the gases with water mist, using a high-speed camera to capture faint flashes of microlightning in the vapor. When they examined the bulb's contents, they found organic molecules with carbon-nitrogen bonds. These included the amino acid glycine and uracil, a nucleotide base in RNA. 'We discovered no new chemistry; we have actually reproduced all the chemistry that Miller and Urey did in 1953,' Zare said. Nor did the team discover new physics, he added — the experiments were based on known principles of electrostatics. 'What we have done, for the first time, is we have seen that little droplets, when they're formed from water, actually emit light and get this spark,' Zare said. 'That's new. And that spark causes all types of chemical transformations.' Lightning is a dramatic display of electrical power, but it is also sporadic and unpredictable. Even on a volatile Earth billions of years ago, lightning may have been too infrequent to produce amino acids in quantities sufficient for life — a fact that has cast doubt on such theories in the past, Zare said. Water spray, however, would have been more common than lightning. A more likely scenario is that mist-generated microlightning constantly zapped amino acids into existence from pools and puddles, where the molecules could accumulate and form more complex molecules, eventually leading to the evolution of life. 'Microdischarges between obviously charged water microdroplets make all the organic molecules observed previously in the Miller-Urey experiment,' Zare said. 'We propose that this is a new mechanism for the prebiotic synthesis of molecules that constitute the building blocks of life.' However, even with the new findings about microlightning, questions remain about life's origins, he added. While some scientists support the notion of electrically charged beginnings for life's earliest building blocks, an alternative abiogenesis hypothesis proposes that Earth's first amino acids were cooked up around hydrothermal vents on the seafloor, produced by a combination of seawater, hydrogen-rich fluids and extreme pressure. Yet another hypothesis suggests that organic molecules didn't originate on Earth at all. Rather, they formed in space and were carried here by comets or fragments of asteroids, a process known as panspermia. 'We still don't know the answer to this question,' Zare said. 'But I think we're closer to understanding something more about what could have happened.' Though the details of life's origins on Earth may never be fully explained, 'this study provides another avenue for the formation of molecules crucial to the origin of life,' Williams said. 'Water is a ubiquitous aspect of our world, giving rise to the moniker 'Blue Marble' to describe the Earth from space. Perhaps the falling of water, the most crucial element that sustains us, also played a greater role in the origin of life on Earth than we previously recognized.'
