The concept of Origins is often invoked in college and university classes that spend a lecture or two on the birth of the universe, synthesis of the elements, formation of the solar system, accretion of the planets, formation of the atmosphere and oceans, and the emergence of life. From that point on, the large format lower– to middle–level courses such as The Solar System or Earth Systems History , and upper division curricula in Biogeosciences , Geobiology , Microbial Evolution or Planetary Biology , tend either to skip or at best gloss–over the nitty–gritty of what is now known about the incipient chemical and biochemical evolution of the Earth. These courses review in great detail the myriad complexities of contemporary biogeochemical cycles, but students are left to fend for themselves if they are curious about the emergence of life and seek to understand modern ideas on how the biogeochemical cycles actually came to be. Because of this disconnect, a significant gap exists between students generally good understanding of what goes on now, versus their lack of knowledge about initial conditions. There is therefore a need for a new textbook that reviews and reinforces what we know about the establishment of the habitable Earth, its biogeochemical cycles and the potential for applying this knowledge to the search for life–signatures other worlds.
Studies of the origin and early evolution of the biogeochemical cycles in the first half of Earth history ought to be considered as a natural foundation for analysis of how the biophilic elements (e.g. S, P, O, N, C, H, Fe, etc.) cycled in the Proterozoic, and continued to change in the various periods of the Phanerozoic. To really begin to understand how the biogeochemical cycles emerged and evolved in the first few billion years, an approach unique to Early Earth studies is needed. Since the groundbreaking synthesis of Dick Holland s Chemical evolution of the atmospheres and oceans (1984), enormous strides have been made. These were due in large part to the interest generated by texts such as that one, but also because of advances in analytical capabilities, comparative planet studies, and the ever expanding inventory of ancient rocks and minerals. An indication of this is that there are several books that have recently been published which describe various aspects of the chemistry of the young Earth and a long–standing history of journals on the topic. Yet, at least in terms of the above–cited books, none of these focuses on meeting the needs of a course on the origin and evolution of the biogeochemical cycles in terms of depth of content, explanatory background material, or the newest results from this rapidly changing field. For example, Hugh Rollinson s Early Earth Systems , Kurt Konhauser s Geomicrobiology and various texts in Planetary Sciences (e.g. de Pater and Lissauer s Planetary Sciences) are outstanding in their own fields, but only lightly touch on topics of how the biogeochemical cycles emerged. The book proposed here Origin and Evolution of the Biogeochemical Cycles clearly takes its inspiration from Holland s Chemical evolution that, although timeless, is nevertheless nearly a quarter–century old and is in need of an update.
Hence, it makes sense at this time to propose a textbook that explores origins, structured along the outline provided below, and appropriate for a one semester course. The target audience is intermediate to advanced undergraduate and graduate students that major in geology, biology, physics, astronomy, chemistry, and planetary sciences. Because the target audience will probably have a diverse skill set, the fundamentals of matter, energy and their interactions will be intercalated with the topics presented, but not treated as a separate section since there are plenty of textbooks already out there and available for that. I also propose to include different thought questions in call–out boxes positioned here and there in the text for which there may (or may not!) be an answer within our current state of knowledge. These are meant to reinforce the concepts presented in the text and to challenge the reader to consider ways now or in the future to tackle fundamental problems. Finally, each chapter will contain a summary of key points, questions, exercises and a reading list. In sum, my hope is that such a book could prompt a wider appreciation of how our knowledge of how it all began is crucial to a deeper understanding of how the biosphere presently interacts with the geosphere.
Judging from the extremely long tenure of such books as Chemical Evolution and Earth s earliest biosphere cited above, it is expected (but by no means guaranteed) that this book will have an adequate market niche with a long shelf–life, given that there is little competition. In terms of organization, there will be continuity between the different chapters, so that overlap of topics is structured to build on previously covered ground. A glossary of terms and an extensive index will help speed the process of cross–referencing ideas from across the text. That is not to say that specific units cannot be created from individual chapters, but when one tries to address foundations, it is worth knowing from where the principles derive.
The author is a geologist with considerable experience and a publication record in this field. It is expected that the book can be produced, along with all drafted illustrations with final art produced by in–house Blackwell and contracted artists, within 72 months of inception of the project.
The concept of Origins.
– Historical developments of the ideas and inspirational sources.
– Application of the Origins concept to biology, geology, astronomy, and chemistry.
– Scope and extent of the book.
II. The Physical Chemical Bases of Biogeochemistry.
– Origin of the Fundamental Forces and matter and how these relate to a habitable universe.
– Binding energy of the nuclides and nuclear stability.
– Nuclear reactions and nuclear chemistry that create the biophilic elements.
– Background to cosmogenic nucleosynthesis and the importance of element recycling in the interstellar medium.
– Nucleosynthetic processes in stars that provide the relative proportions of biophilic elements and their isotopes.
– Brief introduction to galaxies, stars, interstellar medium, nebular processes, accretion, planetisimals and planets.
– Nucleocosmochronology, stellar and galactic nuclear and chemical evolution and its bearing on the timing and establishment of (bio)geochemical cycles of rocky worlds in the galaxy.
III. The Biogeochemical elements, isotopes, abundances and chemistry.
– Physical constraints on solar system formation and formational models.
– Nuclear constraints on the age and origin of solar system solids.
– Chemical and mineralogical bounds P,T,X.
– Icy worlds: Jovian planets and icy dwarf planets, comets and dust.
– Rocky worlds: Terrestrial planets and rocky dwarf planets, asteroids, meteors and dust.
– Sources of liquid water, energy resources and organic molecules.
– Comparative astrophysics young solar analogues and dust disks.
IV. Biogeochemical spheres.
– early evolution.
– physical and chemical constraints on composition (S–isotopes, metals, Pu–Xe, noble gases, etc.).
– factors affecting chemical evolution of the atmosphere.
– biological processes operative in atmospheric evolution.
– constraints on composition.
– O–, Sm–Nd, U–Th–Pb, Hf isotopes.
– Major– minor– trace– and REEs.
– Oldest rocks and what they tell about about the earliest conditions.
– A panoply of theories about the origin of life.
– starting components sources and sinks.
– timing of events.
– chemical evolution macromolecules and the origin of information.
– molecular evolution origin of biochemical information.
– biological evolution origin of Darwinian evolution.
– pre–RNA, PNA, p–RNA, RNA and DNA–peptide Worlds.
– Molecular phylogeny of contemporary life and the history of life.
V. Establishment of Biophilic Element Cycles on Earth.
– origin of carbon, carbonaceous matter, organic chemical precursors, uniqueness of carbon chemistry and the presumed universality of carbon–based life..
– origin of oxygen, water, and the geologic history of free oxygen.
– the ubiquity of hydrogen, abundance in space vs. planetary surface, abundance history in the atmosphere.
– origin of sulfur, sulfur compounds, metal–sulfur and organo–sulfur chemistry, role in the origin of life, atmospheric effects on sulfur chemistry, history of sulfur biogeochemical cycling.
– origin of phosphorus, unique role of phosphorus in biological systems, abundance and roles in the origin of life.
– origin of nitrogen, sources of bio–available nitrogen to the early biosphere, the problem of nitrogen sources.
– new advances in transition metal isotope (bio)geochemistry.
– Other biophilic elements to consider (Mn, Mg, Cu, Co, Zn ).
VI. Early Evolution of the Biogeochemical Cycles.
– Co–evolution of the redox sensitive biophilic elements with changes in the reduction–oxidation state of the surface zone driven by changes in planetary chemistry and evolution of metabolic styles..
– Endogenous effects on the Early Evolution of the Biogeochemical Cycles: changes in the composition of the crust, internal heat engine of Earth, atmosphere and ocean composition.
– Exogenous effects on the Early Evolution of the Biogeochemical Cycles: changes in solar luminosity, impactor flux.
VII. Summary of Key Ideas and Future Directions to Consider.
VIII. References Cited.
IX. Appendices (tables of useful data).
X. Index (comprehensive and alphabetized).
The anticipated length of the book will be ∼350 pages but no more than about 400 pages, with illustrations, chapter summaries, problem sets and suggested readings.