Institute for Advanced Study Informal Astrophysics Seminar

ABSTRACT: The final stages of the growth of a planet consist of violently energetic impacts, but new observations of the Moon and Mercury indicate that the energy of accretion does not remove all the water and carbon from the growing planet. Models demonstrate that rocky planets that accrete with as little as 0.01% water produce a massive steam atmosphere that collapses into a water ocean upon cooling. The low water contents required indicate that rocky planets may be generally expected to produce water oceans through this process, and that an Earth-sized planet would cool to clement conditions in just a few to tens of millions of years. These results indicate that most rocky planets in our solar system and rocky exoplanets are likely to have been habitable early in their evolution, increasing the likelihood of life on the estimated 17 billion Earth-sized planets in the Milky Way.