Implications to Bioastronomy

Prominent evolutionary biologists have for the most part been hostile to the Search for Extraterrestrial Intelligence (SETI). Their arguments center on the purported incredible improbability of genuine intelligence emerging (Mayr 1985 see Simpson's now classic statement, 1964). Tipler (1980), the great opponent of SETI, puts it as follows The present-day theory of evolution, the Modern Synthesis, stresses the great contingency of all branches of the evolutionary tree those possible branches...

Present Abiotic Earth Would It Be Habitable

Let B W J Wabiotic where Wo is the present global biotically enhanced chemical weathering rate and Wabiotic is the hypothetical abiotic rate at the same atmospheric carbon dioxide level, surface temperature, V, and A as present. Then, where Ao,A and Vo,V are the present and arbitrary different continental land areas and volcanic metamorphic outgassing rates of carbon dioxide, respectively. Po is the present atmospheric partial pressure of CO2, Pb the partial pressure of CO2 required under...

The Selforganizing Biosphere Theses on Biospheric Evolution

For the strict neodarwinian, the biosphere cannot evolve in the sense that the biota evolves. However, it may be fruitful to explore the consequences of considering the analogues of genotype and phenotype in the biosphere itself, indeed its evolution in a different sense from the usual definition of evolution for transbiological systems (e.g., superficial descriptive social and cultural evolution). Let us be clear that use of the terms genotype and phenotype for the biosphere in the discussion...

The Carbonate Silicate Geochemical Cycle at Ga for an Abiotic Earth Surface Just at the Transition to Biotic

I assume here that the late bombardment, with its potential for continual large sterilizing surface impacts, was over by 3.8 Ga, thus taking this time as the transition time to biotic colonization of the early continents (Oberbeck and Mancinelli 1994). With the assumptions made above, the product of outgassing rate and land area ratios, (V V)(AJ A), at t 3.8 Ga for two limiting models (models a and c) and a preferred model (b) is given in table 8-3. The variation of A Ao, V Vo, and (V VJ(Ao A)...

Estimates of Biotic Enhancement of Weathering from Field Studies

Ferrihydrite Reddish Brown

The earliest study attempting to estimate the effect of vegetation on chemical weathering rates was apparently that of Cawley et al. (1969). Their estimate of biotic enhancement was about 3, based on a comparison of bicarbonate concentrations (not fluxes, which would be expressed for example as moles km 2 yr_1) in water draining barren and vegetated basalt lava in Iceland. They concluded that plants have had only modest effects on chemical weathering. Several caveats are in order in the...

Introduction to Weathering and Soil Formation

We will not attempt here to duplicate the comprehensive reviews of chemical and physical weathering published elsewhere (Berner and Berner 1987 Drever 1988 White and Brantley 1995). Before systematically considering the weathering process, first an observation on its usual treatment. For the most part, geology textbooks treat the process ofweathering as either physical (mechanical) or chemical. Biological weathering is either not mentioned or discussion is limited to a couple of examples (e.g.,...