Water giant planets

Science, 283, 44 (1999). Superionic and Metallic States of Water and Ammonia at Giant Planet Conditions. 

Gravitational stirring of icy planetesimals by the giant planets could have sent many comets careening into the inner solar system, providing a mechanism for late addition of water to the terrestrial planets. Comets impacting the Earth and the other terrestrial planets would have delivered water as ice (Owen and Bar-Nun, 1995 Delsemme, 1999), whereas the accretion of already altered carbonaceous chondrite asteroids would have delivered water in the form of hydroxl-bearing minerals (Morbidelli el al., 2000 Dauphas et al., 2000). 

The recent advances in modem technology continue to open new opportunities for the observation of chemical reactions on shorter and shorter time scales, at higher and higher quantum numbers, in larger and larger molecules, as well as in complex media, in particular, of biological relevance. As an example of open questions, the most rapid reactions of atmospheric molecules like carbon dioxide, ozone, and water, which occur on a time scale of just a few femtoseconds, still remain to be explored. Another example is the photochemistry of the atmospheres of nearby planets like Mars and Venus or of the giant planets and their satellites, which can help us to understand better the climatic evolution of our own planet. 

Planet formation unfolds differently beyond the snowline, where water condensation enhances the surface density. Here massive cores (> 5-10 MEarth) may form rapid enough to accrete directly and retain nebular gas. These massive cores, if formed prior to the dispersal of the gas disk, rapidly reach Jupiter masses, forming giant planets. An alternative mechanism that may be responsible for the formation of some giant planets is gravitational instability in a massive, marginally unstable disk (e.g. Boss 2007 Mayer etal. 2007). 

C. Cavazzoni, G. L. Chiarotti, S. Scandolo, E. Tosatti, M. Bernasconi, and M. Parrinello (1999) Superionic and metallic states of water and ammonia at giant planet conditions. Science 283, p. 44... 

The very stable molecules CO (observed) and N2 (not observable) are the major C-, 0-, and N-bearing gases throughout the entire CSE, as expected from thermochemical equilibrium. Under the low total pressures in the CSE, conversions of CO to CH4 or N2 to NH3 as the major C- or N-bearing gases does not occur. Even if pressure conditions were favorable, these reactions would not reach equilibrium because they are kinetically inhibited (these conversions are quenched even in the much denser giant planet atmospheres (e.g., 54). This does not mean that CH4 or NH3 should be absent from the CSE it only means that their abundances are likely less than that expected from thermochemical equilibrium. In 0-rich CSE, most oxygen is evenly distributed between CO and H2O, but CO2, produced by the rapid water gas reaction (CO + H2O = H2 + CO2) is also an abundant gas (54) and has been observed. 

The periodic table set iron s density, abundance, and solidity, which created this shield. Mars, Venus, and Titan currently have no magnetic field, which lets the solar wind destroy gas molecules like water. (Mars had one but lost it.) The gas giant planets have magnetic fields from the flow of gas, but only Earth has enough flow inside itself to be both rocky and magnetic for billions of years. 

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