Purpose: Students will work in groups to develop a recipe for life and will learn how evidence from different scientific disciplines contributes to the understanding of the development of life in the universe.
Procedural overview: After reading the Science News article “Life on Earth may have begun in hostile hot springs,” students will research the conditions scientists think are necessary for the formation of organic molecules and living things and then work in groups to develop a “recipe” for life based on physical, chemical, geological, astronomical and biological principles. They also will discuss the role of interdisciplinary research in understanding the origins of life on Earth and the pursuit of life elsewhere in the universe. (A version of “Life on Earth may have begun in hostile hot springs” appeared in the September 26, 2020 issue of Science News, with the title “Did life begin in a place like this?”)
Make it a virtual lesson: Post the link to the Science News article “Life on Earth may have begun in hostile hot springs” to your virtual classroom. Ask students to read the article for homework and prepare for online class by answering the first question. Before the class meets, provide the students with the links to all articles they will need for class. Class discussion can be conducted via Zoom; the research and recipe-building components can be conducted in breakout rooms.
Approximate class time: 2 class periods
Supplies:
Paper
Pencils
Create a Recipe for Life student worksheet
Computer with access to the Science News, Science News for Students and Science News in High Schools archives
Interactive meeting and screen-sharing application for virtual learning (optional)
Audio or video-capture equipment and editing software (optional)
Directions for teachers:
Background
Scientists generally agree that Earth formed from the coalescence of debris from a solar nebula about 4.6 billion years ago. Due to the motion and collisions of particles during coalescence, the early Earth was largely molten, and the hot, fluid materials differentiated by density to form an iron core at the planet’s center, a rocky mantle and a less dense outer crust. As Earth’s surface cooled, the oceans and atmosphere began to form. The primordial oceans and atmosphere were chemically different from today’s oceans and atmosphere. Those changes are a result of geological, chemical and biological processes.
Evidence from rock and fossil records have helped scientists create a model of the early Earth’s geosphere, atmosphere and oceans. As new discoveries are made, theories about the formation and evolution of Earth’s spheres must change to fit the new evidence. Current evidence suggests that life may have begun on Earth some 4 billion years ago. The exact mechanism by which life originated on Earth is still unknown. Scientists agree that living organisms must have arisen from nonliving matter, a process called abiogenesis. But they don’t agree on the process by which that transition occurred. Known living things all exhibit some basic characteristics, including that they are composed of chains of specific molecules and they self-replicate.
The setup
Consider coordinating with other science teachers to teach this interdisciplinary lesson, which lends itself to combining students from biology, chemistry, physics, earth science and astronomy classes. Teachers could lead the discussions on the topics in their subject specialties.
If you will be working remotely or combining multiple classes, find alternative ways for students to collaborate in real time or in rapid succession to interact as they do the activity. Instead of a live discussion, consider having students in different sections or classes record video presentations or construct interactive web experiences to present their life recipes.
Before the first class, ask students to read the Science News article “Life on Earth may have begun in hostile hot springs” as homework and answer the question that follows. Encourage the students to think about what information is being presented and what information has been left out of the article, as well as gaps in their own understanding of the subject. Students may ask questions about the experiments, the scientists or the conclusions outlined in the article.
1. What did you want to learn more about after reading this article? List at least three questions you have about the origins of life on Earth.
Answers will vary. Possible responses include: What characteristics define the difference between living and nonliving things? How did scientists know which chemical elements and compounds to include in their experiments? What characteristics do scientists use to determine whether their experimental procedures formed organic molecules? How are the molecules formed in these experiments similar to and different from living organisms? What other environmental settings could provide conditions that might result in the formation of these molecules? How similar to modern environmental conditions were the conditions at hot springs and in oceans shortly after the formation of Earth?
Class discussion
Before beginning the class discussion about “Life on Earth may have begun in hostile hot springs,” make sure students understand core concepts about the formation of Earth and the origin of life on Earth.
After discussing student answers to the homework question for “Life on Earth may have begun in hostile hot springs,” use the remaining time to focus on topics that will help the students conduct the research needed to create their recipes.
Encourage students to identify each scientist’s core discipline and record which environment they support as the likely origin of life and why. Ask students how scientists differentiate between living and nonliving materials and whether the organic molecules formed during scientists’ experiments at hot springs and hydrothermal vents constitute life. If life could begin in the ways described in the article, why haven’t scientists seen the constant development of new life-forms in hot springs and hydrothermal vents?
Have the students answer the following questions as a class before they break into their research groups.
1. What conditions do the scientists mentioned in the Science News article propose are required for the formation of organic or biological materials? How do those conditions differ based on the scientist’s core science discipline, such as biology, chemistry, physics, geology or astronomy?
All of the scientists agree that a few basic conditions are required. Necessary ingredients include certain chemical elements — such as carbon, nitrogen, oxygen, hydrogen and phosphorus — water or another medium in which chemical reactions can occur, and an energy source for the reactions. The scientists all agree that condensation reactions cause molecules to form and connect together to form organic materials. The scientists also agree that moderate to high temperatures were required for the necessary reactions to occur. However, the scientists differ in the conditions they think are required for the condensation reactions. In general, the biologists and chemists agree that wet-dry cycles, in which the chemical mixture in which the molecules formed was repeatedly wetted and then dried, are required. The astrophysicist proposes that the reactions that connect molecules could occur in ocean water, where the alkaline-acidic gradient could act as a battery to supply the energy for chemical reactions without the wet-dry cycles.
2. Are the scientists mentioned in the Science News article creating new life in their experiments? Support your claim with evidence and scientific reasoning.
No, none of the scientists mentioned in the article are generating new life from nonliving materials. All of the experiments described in the article describe ways that organic molecules may form or join together to form more complex structures. But none of the experiments has generated a fully functioning, living organism that meets all of the requirements of life.
Research conditions necessary for life
Provide students with links to Science News archive and other online resources to help them identify the components necessary for life to develop in environments where life is not known to exist. Then assign students to their groups by scientific discipline. If you are combining biology and chemistry classes, you could have the biology students research and construct their recipes based on biological and geological principles and have the chemistry students base their recipes on chemistry and physics principles.
Make sure each group understands the expectations for the type of information students should find and record. You may wish to construct a simple rubric for groups to follow to ensure they complete the task sufficiently to contribute to the class discussion. To support collaboration, consider having students use a Google doc or some other platform that will allow members of each group to work simultaneously and to give one another immediate feedback.
If this portion is being done with several classes in virtual breakout rooms, it might be helpful to assign teachers to the breakout rooms to address questions from the groups.
1. Identify the scientific discipline on which you will base your recipe.
Answers will vary. Sample answer: I will be using a chemistry focus to develop my recipe.
2. List some search terms you will use to research articles and resources about the building blocks for life.
Answers will vary. Sample answer: Some search terms I can use include origin of life, biochemistry, primordial, fossil cells and life history.
Biology focus
1. What are the basic characteristics of life? How do scientists determine whether an entity is living or nonliving?
Living things are composed of cells; they obtain and use energy; they remove wastes from the body; they grow and develop; they can reproduce; and they respond to stimuli in the environment. In general, an entity is classified as living only if it meets all of the criteria for life. If an entity has only some of the characteristics — like a virus, which meets most of the criteria but cannot replicate its genetic material without an external host — it is generally considered nonliving.
2. What “ingredients” are necessary for known living things to survive? List as many ingredients as you can, including both complex components and their constituents. Then, mark each ingredient on your list as essential or optional.
Living things need water, carbon, nitrogen, oxygen, calcium, phosphorus, hydrogen, salts, minerals and many trace elements. These chemicals combine into compounds and complex molecules to form lipids (fats), amino acids, nucleic acids, proteins, carbohydrates and vitamins. In addition, living things need a source of energy for carrying out life processes. That energy can come from the sun, from chemical reactions, from geothermal sources or from nuclear sources. All of these ingredients are essential for known living things to survive, grow and reproduce.
3. What environmental conditions are necessary for most living things to survive on Earth? Have any known organisms survived outside of those conditions?
Most living things survive within a narrow range of temperatures and pressures on, below or near Earth’s surface. Some organisms can survive in extreme environments, such as at temperatures above the boiling point or below the freezing point of water. Some organisms can survive in dry deserts, and some make their homes in very salty desert lakes. Bacteria and a few fungi have even survived in space. Scientists think that life similar to that on Earth is possible on planets or moons throughout the universe that share some of these characteristics, but no definitive proof of life beyond Earth has been identified.
4. What are the prevailing hypotheses in biology that describe how organic compounds might have gotten to Earth or formed on Earth?
Biologists generally agree that life on Earth originated from nonliving chemical systems, in a process called abiogenesis. The exact mechanisms for abiogenesis are unknown, but most scientists agree that a mixture of chemical elements and compounds in water (commonly referred to as “primordial soup”) on Earth is the source of life’s building blocks. With the addition of energy, such as electrical energy from lightning strikes or nuclear energy from radioactive decay of elements, organic molecules formed and grew and eventually began to replicate. Many biologists also support the RNA world hypothesis, which suggests that RNA molecules formed in the primordial soup. According to the theory, as soon as simple RNA molecules formed, they were able to copy themselves without assistance from other molecules, and these replicating molecules eventually evolved to form DNA and proteins.
Chemistry focus
1. What chemical “ingredients” are essential for life as we know it? List as many substances as you can.
Scientists have determined that living things are composed of certain chemical elements, including oxygen, nitrogen, hydrogen, carbon, phosphorus and sulfur.
2. How do we determine whether a chemical substance is essential for life? How about whether it is produced by living things?
The fact that these elements combine to form the compounds and molecules — nucleotides, nucleic acids, amino acids, proteins and lipids (fats), for example — that make up all known cells is the evidence that they are essential for life. Some substances have been found to form only through specific chemical and physical processes that occur within living things, and those substances or by-products, such as phosphine gas, are used to indicate the presence of living things in an environment.
3. What processes must the ingredients you identified go through to change from their separate identities into a functioning living unit? Describe the steps, in chronological order, that must occur to change the nonliving substances into a living organism.
First, chemical elements must undergo reactions to form compounds, such as water, ammonia and carbon compounds. Then those compounds and other elements combine to form small organic molecules such as amino acids and nucleotides. Additional chemical reactions cause the smaller organic molecules to form long chains such as proteins and nucleic acids, in a process called polymerization. These complex molecules are concentrated in droplets surrounded by membranes formed by other complex molecules called lipids. Somehow, those droplets developed the ability to copy themselves.
4. What conditions are necessary for the processes to occur? For example, do the steps require certain concentrations of ingredients or proportions of substances? Do the processes take a certain amount of time or require a certain type or amount of energy?
Conditions that are suitable for chemical reactions, especially oxidation-reduction reactions, to occur include concentration of chemical substances in one place, the presence of substrates on which chemical reactions can occur and the presence of liquids with high surface tensions, such as water. Some reactions require additional catalysts, such as input or removal of energy as heat or electrical energy. In particular, polymerization requires claylike materials to serve as sites for the organization and formation of the chains. The formation of droplets generally must occur in water or another liquid mixture. The wet-dry cycles described in the Science News article are one example of conditions in which energy is added or removed from the system by condensation and evaporation.
5. What are the prevailing hypotheses in chemistry that describe how organic compounds might have gotten to Earth or formed on Earth?
Chemists generally support the theory of abiogenesis, in which living things on Earth developed from nonliving chemical mixtures as a result of chemical and physical processes. There is much speculation about the composition of the primordial soup, and new hypotheses related to the “messy chemistry” of that substance have gained traction in recent years. Many chemists also support the RNA world hypothesis, which suggests that RNA molecules formed in the primordial soup, but with a twist. According to that idea, instead of RNA molecules directly assembling identical replicas of themselves, the process instead involved sequences of cyclical chemical reactions that reduced the energy levels of electrons in the molecules, which then resulted in the replication of a variety of molecules.
Physics focus
1. Physics and chemistry are sometimes grouped together in a discipline called “physical sciences.” How does the focus of physics differ from that of chemistry? How does that affect how physicists view the origins of life on Earth?
Chemistry tends to focus on matter, and physics focuses on energy and motion. As a result, when physicists think about the origins of life, they tend to focus less on the chemical elements involved and more on the sources, transfers and transformations of energy involved.
2. What sources of matter and energy were likely available on Earth 4 billion years ago? How do living things acquire and use energy today?
The early Earth formed from accretion of materials in the solar nebula. Sources of matter on the early Earth included the material that had coalesced from space dust. Rocks that formed Earth’s surface, gases that were released from Earth’s interior and additional matter that collided with Earth as the planet and its moon continued to form were all part of the mix. Energy in the early Earth system included solar radiation from the new sun, heat energy from the collision of particles to form Earth, the energy of chemical reactions and radioactive decay of elements in the newly formed Earth’s interior and crust. Because living things need energy to carry out processes such as growth and reproduction, a source of energy is essential for the existence of life. Modern organisms get energy from the sun, from geothermal vents and geothermal springs, from radioactive decay of elements and from chemical substances and reactions.
3. What processes or conditions required for the origin of living things can be explained by transfers and transformations of energy?
Energy is stored within the chemical bonds between elements in chemical compounds and molecules. Chemical reactions are described as endothermic or exothermic, meaning that they either release energy or they absorb energy. In many chemical reactions within living things, chemical energy is released to provide energy for life processes. In other processes, chemical energy is stored as substances like proteins and lipids form. Therefore, all of the chemical reactions and processes involved in the formation of the building blocks of life, as well as the chemical reactions and life processes of living things, can be explained in terms of energy transfers or transformations.
4. What are the prevailing hypotheses in physics that describe how organic compounds might have gotten to Earth or formed on Earth?
Many physicists support some version of the theory of abiogenesis and the RNA world hypothesis and are working to find ways to apply physics to those ideas. One provocative new approach is the dissipation-driven adaptation hypothesis. This hypothesis uses the second law of thermodynamics, also called the law of increasing entropy, which states that energy tends to disperse or spread out over time. The hypothesis states that as chemical substances interact over time, they will adopt configurations that spread the energy in the system out among the particles until an equilibrium is reached. Self-replication is a mechanism by which a system of molecules in a liquid mixture, such as the ocean or the primordial soup, could dissipate energy over time. Other physicists, particularly those who also study astronomy, support the idea of exogenesis, or panspermia, which states that life (or at least its chemical precursors) originated elsewhere in the universe and was brought to Earth by space dust, comets, asteroids, meteorites or other colliding space debris.
Earth science focus
1. What are the conditions on Earth that make it able to support living things?
Earth is far enough from the sun that solar energy does not burn off the atmosphere, but the energy is still strong enough to warm Earth’s surface. Earth’s surface is protected by an atmosphere made of gases that keep Earth’s surface within a specific temperature range. Earth’s rocks, oceans, atmosphere and living things are composed of the chemical elements that living things need to survive, such as oxygen, carbon, hydrogen, phosphorus and nitrogen. These materials cycle through Earth’s subsystems so that necessary materials are constantly available and so that the Earth’s environments maintain equilibrium.
2. What were the conditions on Earth when it first formed? How are those conditions similar to and different from the conditions on Earth where living things can be found now? At what point in Earth’s history would conditions that could support life have arisen?
Earth formed by collisions and coalescence of rocks, dust and debris as the early solar system collapsed within a solar nebula. When Earth was forming, the surface was very hot, and most of the surface was molten lava. Over millions of years, Earth’s surface cooled, and a crust of solid rock began to form, but the surface remained very hot and volcanically active. Scientists think that around 4.4 billion years ago, Earth’s oceans began to form, and scientists think that the early oceans were about 1.5 to 2 times saltier than oceans are today. At about the same time the oceans formed, an early atmosphere composed of carbon dioxide, water and ammonia formed. Free oxygen was rare in the early atmosphere, and over the next few billion years, oxygen levels in the atmosphere began to rise. Fossil evidence from crystals that formed 4.1 billion years ago suggest that simple living things might have emerged at that time, but the earliest known fossils of cells come from rocks about 3.5 billion years ago. Most geologists agree that the conditions on Earth around 4 billion years ago could have supported early, simple forms of life.
3. How do living things on Earth acquire the materials and energy they need to sustain life processes?
Living things on Earth acquire matter and energy through a variety of processes. Some microorganisms acquire energy and nutrients from geothermal vents at the bottom of the oceans or near areas of volcanic activity. Plants absorb energy from the sun and acquire energy, as well as chemical elements and compounds, from the soil. Animals get matter and energy from eating plants and other animals. Earth’s ecosystems include many processes that cycle essential nutrients, such as nitrogen, carbon and water, through the land, oceans and atmosphere. Some of those processes occur within minutes, days or years. Other processes take millions of years.
4. What are the prevailing hypotheses in geology or earth science that describe how organic compounds might have gotten to Earth or formed on Earth?
Geologists and paleontologists subscribe to several hypotheses about the origin of life, many of which are variations on abiogenesis. These scientists are split in terms of their support for the different settings in which abiogenesis occurred, although most support the idea that both geothermal hot springs and seafloor geothermal vents may have played roles in life’s origin. However, many geologists also support variations of the hypothesis of exogenesis, or panspermia. There are clues in the geologic record consistent with all of these different ideas, including the formation and chemical composition of Earth’s crust and early oceans, the widespread geothermal and tectonic activity of early Earth and the bombardment of the newly formed planet by space debris.
Astronomy focus
1. What chemical combinations do astronomers think could signal the presence of life on other bodies throughout the universe?
Astronomers looking for life on other planets or moons throughout the universe generally look for life similar to that on Earth. There are six main chemical elements that are associated with life on Earth: oxygen, hydrogen, carbon, nitrogen, phosphorus and sulfur. Astronomers look for evidence of those six elements on other bodies in the universe to determine whether life may possibly exist on those bodies.
2. What environmental conditions on other planets, moons or other celestial bodies are scientists studying for clues about the origins of life on Earth?
Most astronomers think that for life as we know it to survive on a body other than Earth, the body must orbit a star within the habitable zone, which generally means the region around the star where liquid water can exist. This exact location is affected by the magnitude of the star, its radiation output and the distance of the body from the star or from other nearby stars. An energy source for life processes, such as solar energy, geothermal energy or chemical reactions, is essential. Astronomers also think that having other large bodies, such as larger planets, in the star system is essential, because those large bodies attract objects that would otherwise collide with the potentially habitable planet. And having a protective atmosphere or other barrier to damaging radiation is helpful. Most astronomers think that bodies with active plate tectonics are more likely to support living things. Plate tectonics keeps matter and energy cycling and ensures a more stable atmosphere over long periods of time.
3. Where else might conditions for life exist elsewhere in our solar system and the universe? Describe why scientists have identified those locations as potentially hospitable to life.
In our solar system, astronomers think the following bodies might be capable of supporting life: Europa (moon of Jupiter), Titan (moon of Saturn), Ganymede (moon of Jupiter), Ceres (dwarf planet in the asteroid belt), Enceladus (moon of Saturn), Callisto (moon of Jupiter), Mars, Venus and Triton (moon of Neptune). Scientists have identified a few other exoplanets (planets that orbit stars other than the sun) and exomoons that may meet the criteria for supporting life. These celestial bodies all contain at least the possibility of hosting liquid water at or below the surface, and some likely have extensive oceans below icy crusts. Many have protective atmospheres, and all have sources of energy that could maintain a manageable temperature for living things. Some have active volcanoes or activity that resembles plate tectonics.
4. What are the prevailing hypotheses in astronomy that describe how organic compounds might have gotten to Earth or formed on Earth?
Astronomers tend to be split between the ideas of exogenesis (or panspermia) and Earthly abiogenesis. Because many astronomers think that life may exist on many bodies throughout the universe, any theory of abiogenesis on Earth would have to be independently replicable on other worlds. In addition, astronomers tend to think that there may have been multiple paths that led to the formation of life on Earth.
Construct a recipe
In this phase, students will review the information provided in the Science News article and the other sources they located during the research phase. Once students have researched and identified pertinent information about their discipline, students will analyze the information and develop a recipe that describes the components thought to be necessary for generating life. Students will then need to distill the information they have determined to be essential into a recipe format, including ingredients, conditions and procedural steps. You might need to help students identify key information and discard extraneous information.
Ask the students to organize the information they gathered during their research into the format of a recipe, including “ingredients,” conditions and instructions. Have them include as much detail as possible to ensure that someone following the recipe would succeed at creating life. Here are a few prompts to try with your students after they have created the recipe.
How did you determine that your recipe included all of the essential components and no extraneous components?
Is there any information missing from your recipe or any steps that need more details?
Do you think the missing information is available through a different scientific discipline? Support your explanation with evidence and scientific reasoning.
Sample chemistry recipe:
Ingredients: oxygen, nitrogen, hydrogen, carbon, phosphorus, sulfur, compounds of those elements, energy
Conditions: concentrated chemical elements and compounds in a liquid water mixture, high temperatures, and alternating wet and dry conditions caused by repeated condensation and evaporation
Instructions:
1. Create a chemical mixture in hot water containing oxygen, nitrogen, hydrogen, carbon, phosphorus, sulfur and compounds of those elements.
2. Add thermal, electrical or chemical energy to the mixture to cause chemical elements to react to form compounds, such as water, ammonia and carbon compounds.
3. Transfer energy to and from the mixture to initiate chemical reactions that form small organic molecules such as amino acids and nucleotides.
4. Add substrates on which polymerization reactions can occur so that the smaller organic molecules form long chains such as proteins and nucleic acids.
5. Concentrate the complex molecules in a liquid mixture with high surface tension so that they form lipid membranes to contain the proteins and nucleic acids.
Synthesize a model
After student groups have completed a recipe based on their assigned scientific discipline, groups should share their recipes with the class. Allow enough time for the groups to briefly present their recipes. Then, facilitate a class discussion about the commonalities and differences among the different recipes and guide the students as they synthesize the information into a single recipe for life using the question below. If time is limited, analysis of the different recipes and construction of a final recipe could be assigned as homework.
Use this time to assess individual and group progress. Students should demonstrate an understanding of how different scientific disciplines contribute to the overall scientific debate about the mechanisms by which life began on Earth. Students should also recognize that scientific explanations and models can change as new evidence is discovered and presented and that much essential information is still unknown.
1. As a class, choose one recipe to modify to make a final multidisciplinary recipe for originating life. Make changes to the recipe until the class agrees that this is the most complete and likely recipe the class can create. Describe what you did.
We chose to modify the chemistry recipe. We added sources of energy from the physics recipe to the ingredients. We added information about the conditions on Earth around 4 billion years ago to the conditions part of the recipe, and we used information from the astronomy recipe to support those additions. We used information about the basic characteristics of living things to identify whether the recipe was successful. We excluded some information from the astronomy recipe, because our recipe assumes that life originated on Earth and not from an extraterrestrial source.
Sample recipe:
Ingredients: oxygen, nitrogen, hydrogen, carbon, phosphorus, sulfur, compounds of those elements and energy (thermal, electrical or radiation)
Conditions: concentrated chemical elements and compounds in a salty liquid water mixture, high temperatures, low oxygen atmosphere, alternating wet and dry conditions and strong solar radiation
Instructions:
1. Create a chemical mixture in hot, salty water containing oxygen, nitrogen, hydrogen, carbon, phosphorus, sulfur and compounds of those elements.
2. Add thermal, electrical, chemical or radioactive decay energy to the mixture to cause chemical elements to react to form additional compounds, such as water, ammonia and carbon compounds.
3. Transfer energy to and from the mixture to initiate chemical reactions that form small organic molecules such as amino acids and nucleotides.
4. Add substrates on which polymerization reactions can occur so that the smaller organic molecules form long chains such as proteins and nucleic acids.
5. Concentrate the complex molecules in a liquid mixture with high surface tension so that they form lipid membranes to contain the proteins and nucleic acids.
6. Allow to “cook” for an unknown amount of time, up to millions of years, until living things with the following characteristics appear: They are composed of cells; they obtain and use energy; they remove wastes from the body; they grow and develop; they can reproduce; and they respond to stimuli in the environment.
2. How did the sharing of scientific knowledge and peer review of your work help improve your final recipe? How do these habits enhance the development of scientific theories and the advancement of science?
By seeing what other groups created and sharing our recipes, we were able to incorporate different perspectives and unique information from other fields so that we could generate a more complete and accurate description of how life likely began. Sharing of scientific knowledge and peer review of scientific research expose scientists to new ideas and also help maintain the integrity of scientific research by ensuring that scientific studies are performed according to specific standards. This increases the level of trust scientists can have in the data and in conclusions drawn based on the evidence. It allows scientists to check current theories and adapt them to fit the evidence. It also allows scientists to check explanations against a larger pool of evidence and to ask new questions and construct new experiments.
Additional resources
Science News and Science News for Students articles:
Droplets of these simple molecules may have helped kick-start life on Earth
Cooking up life for the first time
Why just being in the habitable zone doesn’t make exoplanets livable
Hope for life on Venus survives for centuries against all odds
Microbiologists took 12 years to grow a microbe tied to complex life’s origins
Fossils offer new candidate for earliest life
Asteroid impacts may have sparked life on Earth
News Brief: Rare gem may hold earliest sign of life
Meteorites may have sparked life on Earth
Space cloud may hold clue to life’s origins
Interstellar chemical resembles building blocks of life
Rules guarding other planets from contamination may be too strict
Other resources:
Bruce Damer and David Deamer. The hot spring hypothesis for an origin of life. Astrobiology. April 2020.
David Deamer, Bruce Damer and Vladimir Kompanichenko. Hydrothermal chemistry and the origin of cellular life. Astrobiology. December 2019
T. Djokic et al. Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits. Nature Communications. Published online May 9, 2017.
E.A. Eloe-Fadrosh et al. Global metagenomics survey reveals a new bacterial candidate phylum in geothermal springs. Nature Communications. Published online January 27, 2016.
B.T. Burcar et al. RNA oligomerization in laboratory analogues of alkaline hydrothermal vent systems. Astrobiology. Vol. 15, July 2015.
M. Ferus et al. High-energy chemistry of formamide: A unified mechanism of nucleobase formation. Proceedings of the National Academy of Sciences. Published online Dec. 8, 2014.
E.A. Bell et al. Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon. Proceedings of the National Academy of Sciences. Published early online October 19, 2015.
B. Patel et al. Common origins of RNA, protein and lipid precursors in a cyanosulfidic protometabolism. Nature Chemistry. Published online March 16, 2015.
A. Méndez et al. A general mass-energy habitability model. The Lunar and Planetary Science Conference, The Woodlands, Texas, March 22, 2018.
R.K. Kopparapu et al. Habitable zones around main sequence stars: New estimates. The Astrophysical Journal. Published online February 26, 2013.
Matthew Powner, Béatrice Gerland and John D. Sutherland. Synthesis of activated pyrimidine ribonucleotides in prebiotically plausible conditions. Nature. May 14, 2009.