Evolution of planets

Atmospheres are a natural consequence of the origin and evolution of planets. If planets are of sufficient size, they may have captured some nebular gas while they formed. Accretionary and radioactive heating can also release gases that were brought into the planet in solid carriers. The atmospheres of Venus, Earth, and Mars are composed of the same gases (C02, N2, H20, 02), but in markedly different amounts and proportions, reflecting their different evolutionary histories. For example, the rise of life on Earth... 

Cosmochemislry places important constraints on models for the origin of the solar nebula and the formation and evolution of planets. We explore nebula constraints by defining the thermal conditions under which meteorite components formed and examine the isotopic evidence for interaction of the nebula with the ISM and a nearby supernova. We consider how planetary bulk compositions are estimated and how they are used to understand the formation of the terrestrial and giant planets from nebular materials. We review the differentiation of planets, focusing especially on the Earth. We also consider how orbital and collisional evolution has redistributed materials formed in different thermal and compositional regimes within the solar system. 

Margulis, L. Matthews, C. Haselton, A. Environmental Evolution. Effects of the Origin and Evolution of Planet Earth-, The MIT Press Cambridge. MA, 2000. 

Young E. D. (2001) The hydrology of carbonaceous chondrite parent bodies and the evolution of planet progenitors. Phil. Trans. Roy. Soc. London A 359, 2095-2110. 

We divide the discussion into four topics. In Section 9.1 we are concerned with the one-dimensional thermal equilibrium configuration of an atmosphere in the absence of internal motion. In Section 9.2 we expand the temperature field to three dimensions and investigate the dynamical properties of atmospheres. In Section 9.3 we address the question of how determinations of chemical composition imply the evolution of planets and the Solar System as a whole. Finally, in Section 9.4 we review measurements of the excess heat emitted by the planets, and discuss the importance of these measurements for determining the status of planetary evolution in the present epoch. 

When considering how the evolution of life could have come about, the seeding of terrestrial life by extraterrestrial bacterial spores traveling through space (panspermia) deserves mention. Much is said about the possibility of some form of life on other planets, including Mars or more distant celestial bodies. Is it possible for some remnants of bacterial life, enclosed in a protective coat of rock dust, to have traveled enormous distances, staying dormant at the extremely low temperature of space and even surviving deadly radiation The spore may be neither alive nor completely dead, and even after billions of years it could have an infinitesimal chance to reach a planet where liquid water could restart its life. Is this science fiction or a real possibility We don t know. Around the turn of the twentieth century Svante Arrhenius (Nobel Prize in chemistry 1903) developed this theory in more detail. There was much recent excitement about claimed fossil bacterial remains in a Martian meteorite recovered from Antarctica (not since... 

The evolution of life on Earfh has depended on a sustained supply of nutrients provided by the physical environment. Life, in turn, has profoundly influenced the availability and cycling of these nutrients hence the inclusion of bio in biogeochemical cycles. The involvement of the biosphere with biogeochemical cycles has been determined by the evolution of life s biochemical properties in the context of the physical and chemical properties of planet Earth. 

Tajika, E. and Matsui, T. (1990) Evolution of terrestrial proto-C02 atmosphere with thermal coupled history of the Earth. Earth Planet. Sci. Lett., 113, 251-266. 

Blichert-Toft J, Alberede F (1997) The Lu-Hf isotope geochemistry of chondrites and the evolution of the mantle-crast system. Earth Planet Sci Lett 148 243-258... 

Bourdon B, Zindler A, Womer G (1994) Evolution of the Laacher See magma chamber evidence from SIMS and TIMS measurements of U-Th disequilibria in minerals and glasses. Earth Planet Sci Lett 126 75-90... 

O Hara MJ (1968) The bearing of phase equilibria studies in synthetic and natural systems on the origin and evolution of basic and ultrabasic rocks. Earth Sci Rev 4 69-133 O Nions RK, McKenzie D (1993) Estimates of mantle thorium/uranium ratios from Th, U and Pb isotope abundances in basaltic melts. Phil Trans Royal Soc 342 65-77 Oversby V, Gast PW (1968) Lead isotope compositions and uranium decay series disequilibrium in reeent volcanic rocks. Earth Planet Sci Lett 5 199-206... 

Griffiths RW (1986) The differing effects of compositional and thermal buoyancies on the evolution of mantle diapirs. Phys Earth Planet Inter 43 261-273... 

With the number of known exoplanets increasing very fast, current results are giving us the chance to undertake the first statistical studies of the properties of the exoplanets, as well of their host stars [24,21,8]. This is bringing new interesting constraints for the models of planet formation and evolution. 

The studies of other elements in metal-rich planet-host stars is also giving important information about the chemical evolution of the Galaxy. 

The discovery of the average metal-rich nature of planet-harbouring stars with regard to disc stars (i.e. [1],[2], [3]) has revealed the key role that metallicity plays in the formation and evolution of planetary systems. If the accretion processes were the main responsible for the iron excess found in planet host stars, volatile abundances should show clear differences in stars with and without planets, since volatiles (with low Tc) are expected to be deficient in accreted materials [4]. Previous studies of the abundance trends of the volatiles N, C, S and Zn [5, 6] have obtained no anomalies for a large sample of planet host stars. 

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