A postulate to assess ‘habitability’

2004 ◽  
Vol 3 (2) ◽  
pp. 157-163 ◽  
Author(s):  
Charles S. Cockell ◽  
Frances Westall
Keyword(s):  
Environmental Conditions ◽  
Early Earth ◽  
Earth Environment ◽  
Chemical Conditions ◽  
Physical And Chemical ◽  
Early Earth Environment

One principal challenge in biology is defining a postulate by which the habitability of other planets can be assessed. Current assessments suffer from two potential weaknesses. With respect to other planets, either assumptions are made about the physical and chemical conditions of environments that err on the side of biological optimism without empirical constraint by spacecraft observations or novel physiologies of microorganisms are invented to fit extraterrestrial environmental conditions with no demonstrated microbiological counterparts on Earth. Attempts to assess the habitability of the early Earth suffer from similar problems. We discuss the following postulate: ‘the proposition that a planet is or was habitable requires that the physiological requirements of microorganisms on Earth known at the time of assessment match the empirically determined combined physical and chemical conditions in the extraterrestrial or early Earth environment being assessed’ as a means of evaluating ‘habitability’. We use as tests for our postulate the early Earth and the cloud deck of Venus (a habitat that has been a source of optimistic debate for forty years). We conclude that, although the early Earth was habitable, Venus is a dead world.

scholarly journals Origin of Life on Mars: Suitability and Opportunities

Life ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 539
Author(s):  
Benton C. Clark ◽  
Vera M. Kolb ◽  
Andrew Steele ◽  
Christopher H. House ◽  
Nina L. Lanza ◽  
...  
Keyword(s):  
Origin Of Life ◽  
Energy Sources ◽  
Early Earth ◽  
Sediment Samples ◽  
Life On Mars ◽  
Eventual Return ◽  
History Of ◽  
Early Mars ◽  
Chemical Conditions ◽  
Physical And Chemical

Although the habitability of early Mars is now well established, its suitability for conditions favorable to an independent origin of life (OoL) has been less certain. With continued exploration, evidence has mounted for a widespread diversity of physical and chemical conditions on Mars that mimic those variously hypothesized as settings in which life first arose on Earth. Mars has also provided water, energy sources, CHNOPS elements, critical catalytic transition metal elements, as well as B, Mg, Ca, Na and K, all of which are elements associated with life as we know it. With its highly favorable sulfur abundance and land/ocean ratio, early wet Mars remains a prime candidate for its own OoL, in many respects superior to Earth. The relatively well-preserved ancient surface of planet Mars helps inform the range of possible analogous conditions during the now-obliterated history of early Earth. Continued exploration of Mars also contributes to the understanding of the opportunities for settings enabling an OoL on exoplanets. Favoring geochemical sediment samples for eventual return to Earth will enhance assessments of the likelihood of a Martian OoL.

scholarly journals RNA and the Goldilocks Zone: Where Mg2+ concentration is just right

2021 ◽  
Author(s):  
Rebecca Guth-Metzler ◽  
Ahmad Mohyeldin Mohamed ◽  
Elizabeth T Cowan ◽  
Moran Frenkel-Pinter ◽  
Roger Wartell ◽  
...  
Keyword(s):  
Rna Folding ◽  
Local Maximum ◽  
Rna Cleavage ◽  
Early Earth ◽  
Yeast Trna ◽  
Earth Environment ◽  
Evolutionary Context ◽  
Simulation And Experiment ◽  
Early Earth Environment

Mg2+, the most abundant divalent cation in cells, catalyzes RNA cleavage but can also promote RNA folding. Because folding can protect RNA from cleavage, we predicted a "Goldilocks zone", which is a local maximum in RNA lifetime at the minimum Mg2+ concentration required for folding. By simulation and experiment, we characterized the RNA Goldilocks zone and its dependence on cleavage parameters and extent of folding. We show experimentally that yeast tRNAPhe can inhabit a Goldilocks zone. The Goldilocks phenomena appears to be robust and is tunable by changes in magnesium affinity, and a variety of other factors. Goldilocks behavior can be more pronounced for RNAs with intermediate folding states. Goldilocks behavior allows ultrafine control of RNA chemical lifetime. A subset of RNAs in vivo are expected to occupy the Goldilocks zone. In evolutionary context, Goldilocks behavior may have shaped RNA in an early Earth environment containing Mg2+ and other metals. RNAs that do not fold cannot access a Goldilocks zone.

Permeability to albumin in isolated coronary venules

1993 ◽  
Vol 265 (2) ◽  
pp. H543-H552 ◽  
Author(s):  
Y. Yuan ◽  
W. M. Chilian ◽  
H. J. Granger ◽  
D. C. Zawieja
Keyword(s):  
Permeability Coefficient ◽  
Filtration Rate ◽  
Intraluminal Pressure ◽  
Apparent Permeability ◽  
Filtration Pressure ◽  
Diffusive Permeability ◽  
Apparent Permeability Coefficient ◽  
Chemical Conditions ◽  
Physical And Chemical ◽  
Intravascular Pressure

This study reports measurements of albumin permeability in isolated coronary venules. The isolated microvessel technique allows the quantification of transmural exchange of macromolecules under tightly controlled physical and chemical conditions. Transvenular exchange of albumin was studied in isolated coronary venules during alterations in filtration rate caused by changes in intravascular pressure. The apparent permeability coefficient of albumin (Pa) at an intraluminal pressure of 11 cmH2O was 3.92 +/- 0.43 x 10(-6) cm/s. Elevating intraluminal pressure to 16 and 21 cmH2O increased Pa to 5.13 +/- 0.57 x 10(-6) and 6.78 +/- 0.66 x 10(-6) cm/s, respectively. Calculation of the true diffusive permeability coefficient of albumin (Pd) at zero filtration rate was 1.54 x 10(-6) cm/s. The product of hydraulic conductance (Lp) and (1 - sigma), where sigma is the solute reflection coefficient, was 3.25 x 10(-7) cm.s-1 x cmH2O-1. At a net filtration pressure of 4-5 cmH2O, diffusion accounts for > 60% of total albumin transport across the venular wall. Transmural albumin flux is very sensitive to filtration rate, rising 6.7% for each cmH2O elevation of net filtration pressure. At 11 cmH2O net filtration pressure, convection accounts for nearly 70% of net albumin extravasation from the venular lumen. We suggest that the isolated coronary venule is a suitable preparation for the study of solute exchange in the heart.

scholarly journals Differential strengths of molecular determinants guide environment specific mutational fates

2017 ◽  
Author(s):  
Rohan Dandage ◽  
Rajesh Pandey ◽  
Gopal Jayaraj ◽  
Kausik Chakraborty
Keyword(s):  
Protein Folding ◽  
Molecular Evolution ◽  
Protein Stability ◽  
Environmental Effects ◽  
Environmental Conditions ◽  
Fitness Landscape ◽  
Dependent Manner ◽  
The Common ◽  
Physical And Chemical ◽  
Substrate Binding Protein

AbstractUnder the influence of selection pressures imposed by natural environments, organisms maintain competitive fitness through underlying molecular evolution of individual genes across the genome. For molecular evolution, how multiple interdependent molecular constraints play a role in determination of fitness under different environmental conditions is largely unknown. Here, using Deep Mutational Scanning (DMS), we quantitated empirical fitness of ∼2000 single site mutants of Gentamicin-resistant gene (GmR). This enabled a systematic investigation of effects of different physical and chemical environments on the fitness landscape of the gene. Molecular constraints of the fitness landscapes seem to bear differential strengths in an environment dependent manner. Among them, conformity of the identified directionalities of the environmental selection pressures with known effects of the environments on protein folding proves that along with substrate binding, protein stability is the common strong constraint of the fitness landscape. Our study thus provides mechanistic insights into the molecular constraints that allow accessibility of mutational fates in environment dependent manner.Author SummaryEnvironmental conditions play a central role in both organismal adaptations and underlying molecular evolution. Understanding of environmental effects on evolution of genotype is still lacking a depth of mechanistic insights needed to assist much needed ability to forecast mutational fates. Here, we address this issue by culminating high throughput mutational scanning using deep sequencing. This approach allowed comprehensive mechanistic investigation of environmental effects on molecular evolution. We monitored effects of various physical and chemical environments onto single site mutants of model antibiotic resistant gene. Alongside, to get mechanistic understanding, we identified multiple molecular constraints which contribute to various degrees in determining the resulting survivabilities of mutants. Across all tested environments, we find that along with substrate binding, protein stability stands out as the common strong constraints. Remarkable direct dependence of the environmental fitness effects on the type of environmental alteration of protein folding further proves that protein stability is the major constraint of the gene. So, our findings reveal that under the influence of environmental conditions, mutational fates are channeled by various degrees of strengths of underlying molecular constraints.

scholarly journals Ekosistem Mangrove Binuangeun, Banten: Kondisi Fisik Dan Kimia Serta Ragam Ikan

2020 ◽  
Vol 5 (2) ◽  
pp. 32-40
Author(s):  
Fitri Andriyani
Keyword(s):  
Research Method ◽  
Mangrove Ecosystem ◽  
Water Current ◽  
Root Structure ◽  
Chemical Condition ◽  
Literature Study ◽  
Marine Animals ◽  
Mangrove Ecosystems ◽  
Chemical Conditions ◽  
Physical And Chemical

Binuangeun Mangrove Ecosystem is located in the south western Java Island, in the area of ​​Lebak Regency, Banten Province. Mangrove ecosystems are ecosystems that located at the Coastal areas which are a habitat for a variety of marine animals which are associated with it, mostly fish, because of its complex or a very effective root structure which can provide a place for fish to be able to live, take shelter, develop, breed and also look for food. This research was conducted to determine the physical and chemical condition and the variety of fishes which found in the Binuangeu, Banten Mangrove Ecosystem. This research method uses literature study. Physical and chemical conditions of the Binuangeun Mangrove Ecosystem, Banten have degrees of temperature ranging from 28.20 - 32.20; acidity range between 7.00 - 8.09; turbidity ranges from 22.50 - 76.00 NTU; water current ranged from 0.079 to 0.189; phosphate content ranges from 0.02 - 0.008; salinity ranges from 30-35 PSU; and dissolved oxygen content ranges from 5.67 - 8.70. The types of fish found in the Binuangeun Mangrove Ecosystem, Banten are 45 species from 22 Family. The most abundant and relatively high species of existence is the Gobiidae with 10 species.   Keywords: Banten, Binuangeun, Ecosystems, Fish, Mangroves

scholarly journals Peat decomposition – shaping factors, significance in environmental studies and methods of determination; a literature review

Geologos ◽  
2016 ◽  
Vol 22 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Danuta Drzymulska
Keyword(s):  
Chemical Composition ◽  
Literature Review ◽  
Ground Water ◽  
Environmental Conditions ◽  
Meteoric Water ◽  
Climatic Conditions ◽  
Review Of Literature ◽  
Forming Process ◽  
Physical And Chemical

Abstract A review of literature data on the degree of peat decomposition – an important parameter that yields data on environmental conditions during the peat-forming process, i.e., humidity of the mire surface, is presented. A decrease in the rate of peat decomposition indicates a rise of the ground water table. In the case of bogs, which receive exclusively atmospheric (meteoric) water, data on changes in the wetness of past mire surfaces could even be treated as data on past climates. Different factors shaping the process of peat decomposition are also discussed, such as humidity of the substratum and climatic conditions, as well as the chemical composition of peat-forming plants. Methods for the determination of the degree of peat decomposition are also outlined, maintaining the division into field and laboratory analyses. Among the latter are methods based on physical and chemical features of peat and microscopic methods. Comparisons of results obtained by different methods can occasionally be difficult, which may be ascribed to different experience of researchers or the chemically undefined nature of many analyses of humification.

Suspension Plasma Spraying (SPS) of Cobalt Spinel

1997 ◽  
Author(s):  
G. Schiller ◽  
M. Müller ◽  
F. Gitzhofer ◽  
M.I. Boulos ◽  
R.B. Heimann
Keyword(s):  
Plasma Spraying ◽  
Inductively Coupled Plasma ◽  
Solid Phase ◽  
Spinel Phase ◽  
Rf Plasma ◽  
Dry Powders ◽  
Inductively Coupled ◽  
Cobalt Spinel ◽  
Chemical Conditions ◽  
Physical And Chemical

Abstract Fine (median size 6 μm and 0.3 μm) cobalt spinel (Co3O4) powders were processed suspended in a suitable liquid phase. Suspensions exceeding 50 wt.% solid phase content were successfully injected into an inductively coupled plasma. Spheroidized powders with large particle size (up to 80 μm) were prepared, and cobalt oxide coatings were produced by this novel RF-SPS method. The microstructural features of the coatings can be controlled by parameter optimization similarly to plasma spraying of dry powders. Numerous variations of the physical and chemical conditions of the process were performed in an attempt to overcome the main disadvantage of the process, i.e. the decomposition of the spinel phase to CoO. So far, the spinel phase could be reestablished only by a post-treatment of the deposited coatings with atomic oxygen in the RF plasma.

scholarly journals Changes in Potential Evaporation in the Years 1952–2018 in North-Western Poland in Terms of the Impact of Climatic Changes on Hydrological and Hydrochemical Conditions

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 877 ◽  
Author(s):  
Monika Okoniewska ◽  
Danuta Szumińska
Keyword(s):  
Water Resources ◽  
Air Temperature ◽  
21St Century ◽  
Climatic Factors ◽  
Potential Evaporation ◽  
Relative Air Humidity ◽  
Chemical Conditions ◽  
Physical And Chemical ◽  
The Impact ◽  
North Western

The paper analyses changes in potential evaporation E0 (mm) in north-western Poland in the years 1952–2018. E0 (mm) has been calculated according to Ivanov’s formula based on the monthly values of air temperature (t, °C) and relative air humidity (f, %) for six weather stations of the Institute of Meteorology and Water Management. The data were collected using the Statistica software ver. 13 and the QGIS software ver. 3.80. The results indicate statistically significant trends in the increase of E0 during the period 1952–2018, and that it is particularly high during the spring and summer months, which should be associated with a statistically significant increase in air temperature and a decrease in relative humidity at all examined stations. The results also indicate an exceptionally high increase in evaporation since the end of the 20th century and in the 21st century, which reflects a potentially higher risk of permanent changes in hydrological conditions. The research results point to the major role of climatic factors in the often-dramatic decreases in water resources observed in the 21st century, particularly in lakes and small watercourses. The progressing reduction of water resources may cause permanent changes in physical and chemical conditions in waterbodies.

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