Name Instructor Course Date Robert M. Hazen: “Life’s Rocky Start.” 1. Summary of the Article. Robert M. Hazen’s article, “Life’s Rocky Start,” explores the role played by minerals in the origins of life on primitive earth. The particular way in which life on earth originated is still a matter of debate…
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Biological life originates from the replication of carbon-based compounds. The basic carbon-based molecules, present as gases in the atmosphere of early earth, have only single atoms of carbon is each molecule. In order to become the compounds which make up the units of living organisms, these molecules must form complex molecular bonds. These chemical reactions of carbon-based molecules are facilitated by the minerals present in the rocks of primitive earth, through five means. First, minerals shelter carbon molecules, and keep them from breaking down in the harsh conditions of the primitive earth. Stanley L. Miller’s famous laboratory experiment shows that the basic carbon molecules which are the building blocks of life emerge from water and gas. The linking of these simple molecules into the complex molecular structures, which constitute living organisms, is made possible by rocks, which provide shelter in their microscopic pits. The rocks prevent the molecules from breaking down under deadly radiation, high pressure and intense heat, in the extreme conditions near the hydrothermal vents on the ocean floor. The rocks serve as containers to foster life. Second, the rigid surface of minerals provides a scaffolding-like support. Simple carbon molecules can cling together on these surfaces, and react to form complex compounds. Layered minerals, such as clay, have flat, smooth layers of atoms, which attract and hold in place individual molecules. Organic molecules are attracted to these surfaces, where they concentrate, and link themselves into complex organic compounds. Here, the rocks give a supporting framework for the clustering and growth of molecules, ensuring that the delicate amino-acids remain unbroken. Third, the crystal faces of minerals present in the rocks act as templates. These surfaces serve as models, which preferentially select certain primitive molecules, and make them biologically important. All living organisms have an excess of Left-handed amino acids. This is due to the fact that crystal faces preferentially choose left-handed amino acids. The faces of minerals, like calcite, serve as chemical bonding sites, where left-handed amino acids react to form proteins, which then replicate to form the units of life. The rocks actively select the molecules which later become biological building blocks. Fourth, minerals act as catalysts in reactions that convert simple molecules into complex biological compounds. All biological reactions require nitrogen, which they can acquire only from ammonia. However, the only form of nitrogen available in the earth’s early atmosphere is nitrogen gas. Experiments show that magnetite, an iron-oxide mineral, triggers the chemical synthesis of ammonia, from nitrogen gas, and hydrogen, at temperatures and pressures seen on the floor of the ocean. Five, elements of dissolved minerals from rocks are a part of the chemical reactions in which complex organic molecules are manufactured from simple inorganic chemicals. At the high temperatures and pressures present at deep-sea hydrothermal vents, minerals in rocks dissolve. The atoms and molecules which are released go on to become a part of biological enzymes. Experiments show that many common minerals promote carbon fixation. Increasingly complex carbon molecules are manufactured from the water and carbon dioxide available on primitive earth because of minerals acting as reactants. Hazen lists five means by which minerals play
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