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Terrestrial biosphere
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Title: Investigations into the impact of astronomical phenomena on the terrestrial biosphere and climate
Author: Fabo Feng

This thesis assesses the influence of astronomical phenomena on the Earth's biosphere and climate. I examine in particular the relevance of both the path of the Sun through the Galaxy and the evolution of the Earth's orbital parameters in modulating non-terrestrial mechanisms. I build models to predict the extinction rate of species, the temporal variation of the impact cratering rate and ice sheet deglaciations, and then compare these models with other models within a Bayesian framework. I find that the temporal distribution of mass extinction events over the past 550 Myr can be explained just as well by a uniform random distribution as by other models, such as variations in the stellar density local to the Sun arising from the Sun's orbit. Given the uncertainties in the Galaxy model and the Sun's current phase space coordinates, as well as the errors in the geological data, it is not possible to draw a clear connection between terrestrial extinction and the solar motion. In a separate study, I find that the solar motion, which modulates the Galactic tidal forces imposed on Oort cloud comets, does not significantly influence this cratering rate. My dynamical models, together with the solar apex motion, can explain the anisotropic perihelia of long period comets without needing to invoke the existence of a Jupiter-mass solar companion. Finally, I find that variations in the Earth's obliquity play a dominant role in triggering terrestrial deglaciations over the past 2 Myr. The precession of the equinoxes, in contrast, only becomes important in pacing large deglaciations after the transition from the 100-kyr dominant periodicity in the ice coverage to a 41-kyr dominant periodicity, which occurred 0.7 Myr ago.

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Study logs oceans' tiniest life

An unprecedented number of tiny, ocean dwelling organisms have been catalogued by researchers involved in a global survey of the world's oceans.
One of the highlights was the discovery of a vast "microbial mat", covering an area equivalent to the size of Greece.

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Mat of microbes the size of Greece discovered on seafloor

Gargantuan whales and hefty cephalopods are typically thought of as the classic marine mammoths, but they might have to make way for the mighty microbes, which constitute 50 to 90 percent of the oceans' total biomass, according to newly released data.
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Census Releases Deep Sea Findings Beyond Sunlight
Five of the Census 14 field projects plumb the ocean beyond sunlight, each dedicated to the study of life in progressively deeper realms from the continental margins (COMARGE: Continental Margins Ecosystems) to the spine-like ridge running down the mid-Atlantic (MAR-ECO: Mid-Atlantic Ridge Ecosystem Project), the submerged mountains rising from the seafloor (CenSeam: Global Census of Marine Life on Seamounts), the muddy floor of ocean plains (CeDAMar: Census of Diversity of Abyssal Marine Life), and the vents, seeps, whale falls and chemically-driven ecosystems found on the margins of mid-ocean ridges and in the deepest ocean trenches (ChEss: Biogeography of Deep-Water Chemosynthetic Systems).

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From a translucent jumbo octopus to a fish bearing barbed fangs, scientists say they have discovered hundreds of new species living several kilometres beneath the ocean surface and in total darkness.
Researchers probing pitch-black waters from the Antarctic to deep seas off Iceland say they have catalogued about 5,700 marine life forms that have never seen light, with some being new to science.
The data, part of the ongoing Census of Marine Life project, stunned some of the international scientists who say the unexpected finds show how poorly understood the deep seas are and how much more there could be out there.

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About a billion years from now, some scientists say, the sun will be too bright for comfort, and our formerly hospitable planet will no longer be able to support life. If visions of this impending heat death disturb you, researchers from the California Institute of Technology have some good news. Their calculations add at least another billion years to Earths expiration date, results published in the Proceedings of the National Academy of Sciences.

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Roughly a billion years from now, the ever-increasing radiation from the sun will have heated Earth into inhabitability; the carbon dioxide in the atmosphere that serves as food for plant life will disappear, pulled out by the weathering of rocks; the oceans will evaporate; and all living things will disappear.
Or maybe not quite so soon, say researchers from the California Institute of Technology (Caltech), who have come up with a mechanism that doubles the future lifespan of the biosphere - while also increasing the chance that advanced life will be found elsewhere in the universe.
A paper describing their hypothesis was published June 1 in the early online edition of the Proceedings of the National Academy of Science.

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Title: Atmospheric pressure as a natural climate regulator for a terrestrial planet with a biosphere
Authors: King-Fai Li, Kaveh Pahlevan, Joseph L. Kirschvink and Yuk L. Yung

Lovelock and Whitfield suggested in 1982 that, as the luminosity of the Sun increases over its life cycle, biologically enhanced silicate weathering is able to reduce the concentration of atmospheric carbon dioxide (CO2) so that the Earth's surface temperature is maintained within an inhabitable range. As this process continues, however, between 100 and 900 million years (Ma) from now the CO2 concentration will reach levels too low for C3 and C4 photosynthesis, signalling the end of the solar-powered biosphere. Here, we show that atmospheric pressure is another factor that adjusts the global temperature by broadening infrared absorption lines of greenhouse gases. A simple model including the reduction of atmospheric pressure suggests that the life span of the biosphere can be extended at least 2.3 Ga into the future, more than doubling previous estimates. This has important implications for seeking extraterrestrial life in the Universe. Space observations in the infrared region could test the hypothesis that atmospheric pressure regulates the surface temperature on extrasolar planets.

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