Putting the squeeze on planets outside our solar system

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  1. ankur26888

    ankur26888 Regular Member

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    Using high-powered lasers, scientists at Lawrence Livermore National Laboratory and collaborators discovered that molten magnesium silicate undergoes a phase change in the liquid state, abruptly transforming to a more dense liquid with increasing pressure. The research provides insight into planet formation. Just as graphite can transform into diamond under
    high pressure, liquid magmas may similarly undergo
    major transformations at the pressures and
    temperatures that exist deep inside Earth-like
    planets. Using high-powered lasers, scientists at Lawrence Livermore National Laboratory and collaborators
    discovered that molten magnesium silicate
    undergoes a phase change in the liquid state,
    abruptly transforming to a more dense liquid with
    increasing pressure. The research provides insight
    into planet formation. "Phase changes between different types of melts
    have not been taken into account in planetary
    evolution models," said lead scientist Dylan
    Spaulding, a UC Berkeley graduate student who
    conducted most of his thesis work at the
    Laboratory's Jupiter Laser Facility. "But they could have played an important role during Earth's
    formation and may indicate that extra-solar 'Super-
    Earth' planets are structured differently from Earth." Melts play a key role in planetary evolution. The
    team said that pressure-induced liquid-liquid phase
    separation in silicate magmas may represent an
    important mechanism for global-scale chemical
    differentiation and also may influence the thermal
    transport and convective processes that govern the formation of a mantle and core early in planetary
    history. Liquid-liquid phase separation is similar to the difference between oil and vinegar – they want
    to separate because they have different densities. In
    the new research, however, the researchers noticed
    a sudden change between liquid states of silicate magma that displayed different physical properties even though they both have the same composition
    when high pressure and temperatures were
    applied. The team used LLNL's Janus laser and OMEGA at the
    University of Rochester to conduct the experiments
    to achieve the extreme temperatures and pressures
    that exist in the interiors of exoplanets -- those
    objects outside our solar system. In each experiment, a powerful laser pulse
    generated a shock wave while it traveled through
    the sample. By looking for changes in the velocity of
    the shock and the temperature of the sample, the
    team was able to identify discontinuities that
    signaled a phase change in the material. "In this case, the decay in shock-velocity and
    thermal emission both reverse themselves during
    the same brief time interval," Spaulding said. The team concluded that a liquid-liquid phase
    transition in a silicate composition similar to what
    would be found in terrestrial planetary mantles
    could help explain the thermal-chemical evolution
    of exoplanet interiors.

    Http://pda.physorg.com/news/2012-02-planets-solar.html
     
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