The Effect of Accretion Rate and Composition on the Structure of Ice-rich Super-Earths

Abstract It is reasonable to assume that the structure of a planet and interior distribution its components are determined by formation history. We thus follow growth from small embryo through subsequent evolution. estimate accretion rate range based on protoplanetary disk model at large-enough distance central star for water ice be major component. accreted material mixture silicate rock ice, with no H–He envelope, as timescale much longer than time required nebular gas dissipate. adopt thermal evolution includes accretional heating, radioactive energy release, separation rock. Taking Safronov parameter ice-to-rock ratio free parameters, we compute evolutionary sequences different combinations, 4.6 Gyr. find final depend significantly both parameters. Low initial ratios high rates, each resulting in an increased heating rate, lead extended rocky cores, while opposite conditions leave composition almost unchanged result relatively low internal temperatures. When cores form, ice-rich outer mantles still contain mixed ice. considerable fraction evaporates upon accretion, depending it lost, surface bulk density do not necessarily reflect composition.