Robert M. Hazen: Lifes Rocky Start - Essay Example

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. However, they can be no doubt that biological life is the result of chemistry. The raw material for the chemical reactions which led to the origins of life are necessarily air, water and rocks, as these are the only resources available at the time of formation of the earth. 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 a pivotal part in the chemical reactions which lead to the origin of life on earth. The rocks act as containers to shelter carbon molecules from the harsh elements, as supporting scaffolding which holds the fragile molecules, as templates in selecting molecules, as catalyst in the synthesis of ammonia, and as reactants in carbon fixation. Minerals definitely participated in the origins of biological life on earth. 2. Discuss one aspect of the article you understood well. The function of rocks as containers, and as scaffolding is very easy to grasp. As the concept of protective and supportive structures is something which is very much a part of everyday life, this line of argument is very understandable. The fragile, unstable, simple carbon molecules are sheltered from the extreme conditions of the primitive earth by the tiny compartments in the mineral structure. The rocks serve as support structures for the assembly of these molecules and their clustering into more complex molecules. This reminds me of the scaffolding used in construction, which acts as a support for the building blocks. It also brings to mind the rocks which provide firm surfaces which are conducive to the growth of sponges in the oceans. 3. Discuss one aspect of the article you did not understand well. The concept of ‘chirality,’ is rather confusing. The selectivity exhibited by the faces of crystals for left-handed amino acids, and their active preference for this, is difficult to understand. Anyway, the theory that the first self-replicating protein molecule formed on the surface of a crystal face, which preferentially selected left-handed amino acids, seems to be just a conjecture. If both kinds of amino acids ‘line up’ on the calcite faces based on their chirality, why is it that it is only the left-handed amino acids which build up into proteins? The author does not support this argument as well as he does his other theories. 4. Discuss what about the article you found most interesting or informative. Hazen’s article is fascinating to read. His easy-to-understand language, clear explanation of concepts, the illustrations, and examples, make his writing appealing and very informative. Any reader who is curious about the origins of life on earth will find the information presented very interesting. This article has change my entire way of thinking about the origin of life on earth. This has been my earlier picture of the origin of life: an enormous primordial ocean teems with the ingredients of life, as a kind of primordial ‘soup’; the stormy atmosphere flashes with lightening, which strikes the waters; life originates from this interaction of the atmosphere and water! Hazen’s article, listing the various ways in which rocks play a part in this great act of creation, has been an eye-opener. The rocks may be considered to have actually triggered and nurtured early life! The rocks provide protective and supportive means for carbon molecules. The minerals in the rocks provide the chemical ingredients for the origin of life. I will never again be able to look at rocks as ‘just stone.’ A piece of pumice, or calcite, now embodies the wonder of how air, water and minerals interact to give rise to the chain of reactions which made humanity. Works Cited. Hazen, Robert M. “Life’s Rocky Start.” Scientific American. April 2001, Volume 284, Issue 4, p. 76-86. Print. Read More