Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p13c1330j&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #P13C-1330
Physics
5410 Composition (1060, 3672), 5430 Interiors (8147), 5455 Origin And Evolution, 5460 Physical Properties Of Materials
Scientific paper
The chemical composition and structure of super-Earths can be understood from data and models for the chemical evolution of our galaxy, our solar system and models of formation and interiors of planets. Because the relative proportions of most rock-forming elements in stars of our galaxy are rather constant the mineralogy of solid grains that formed in the proto-planetary disks can be estimated from a calculation of condensation of a solar composition gas. Such a calculation shows that the minerals forsterite (Fo) and FeNi metal are the two most abundant solids from which Earth-like planets accrete, and therefore studying the behavior of Fo-metal mixtures at ultrahigh pressures (5-10 TPa) and temperatures is essential for modeling the internal structures of the largest super-Earths. The most critical parameter is the metal/silicate ratio of the planet. What determines the metal to silicate ratio is not well established, but it is most likely related to the amount of metal oxidized by water in planetesimals. Earth-like planets are, by definition, volatile depleted, but do have variable patterns of intermediate to highly volatile elements that are of secondary importance for understanding the chemistry of super-Earths. The deep interiors of the largest super-Earths may be in a WDM (warm dense matter) state which is an atomic fluid that may dissolve most components normally residing in the silicate mantle. We are trying to characterize this state using the high energy density lasers (ZBL and Z-Petawatt) at Sandia National Laboratories. Models of such planets with atomic fluid cores may be substantially different from the standard super-Earth models that have been discussed up to now. In anticipation of the measurement of radii (R) and masses (M) of super-Earths in the coming years (e.g., with NASA's Kepler mission) the standard super-Earth models yielded a scaling law of R ∝ M0.262 - 0.274 for Super-Earths. This law may have to be modified for planets with WDM cores.
Jacobsen Stein B.
O'Connell Rirchard J.
Petaev Michael I.
Remo John L.
Sasselov Dimitar D.
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