The scientific goals of the proposed research are to develop the most comprehensive model thus far for planetesimals bombardment during the Hadean eon (ca. 3.9-4.5 Gyr ago), and their environmental effects, with emphasis on factors that affect life and habitability. We will use state-of-the-art numerical simulations and terrestrial constraints (e.g., highly siderophyle elements) to calibrate the Hadean bombardment flux. The calibrated flux will be used to study the near-surface thermal effects of the impacts, as well as their effects on crustal recycling. The ultimate goal of this research is to make predictions on the fraction of Earth's near-surface volume capable of sustaining liquid water and habitable environments throughout the Hadean. This research addresses major processes relevant for the habitability of the Hadean Earth, and therefore it is relevant to documents ROSES C.5 Exobiology and NASA Astrobiology Roadmap.