Why SuperEarths are not Earthlike

Kepler data indicate that there are many planets that could be Earthlike in the sense of having a similar bulk composition. I will explain why such planets are unlikely to be Earthlike in other respects, especially if they are superEarths (three or so Earth masses or more). There are three main points here: (1) SuperEarths will not separate core from mantle because they are likely to be so hot internally that the critical temperature is reached for miscibility of iron alloy and silicate material. (2) Earth is (so far as we know) special in having a water budget that (expressed as an ocean) corresponds to water depths ~ mountain heights.(3) The surface will be hot either from a massive atmosphere or proximity to the parent star.

Speaker: David Stevenson, California Institute of Technology