Seminar

Due to the enormous discovery of exoplanets, planet formation theory is changing. This talk will present current understanding and discuss difficulty of planet formation. Formation of planetesimals - the building blocks of planets - and orbital migration of planets are the most serious problems.  Based on these, I will discuss the delivery of H2O, C and N to the Earth. Life is made of C and N and they may have been formed by chemical evolution in liquid water. Because these compounds are volatile, they would not be included in planetesimals around Earth's orbit, so that they must be condensed in outer regions and delivered to the Earth by some mechanism. Although there could be many planets in the so-called "habitable zones," in which ocean can exist on their surface, they cannot really harbor life unless H2O, C and N are delivered to the planets.