Enrichment of planetary surfaces by asteroid and comet impacts

Asteroids and comets, or in short minor bodies, likely have played a very important role in the early evolution of the Earth. Some theories suggest that significant amounts of water and organic material, two key ingredients for life as we know it, were delivered to Earth through asteroid and comet impacts. These events have affected not only our Earth but all other planetary surfaces within the Solar System. Moreover, the delivery mechanisms still operate nowadays. We have performed computer simulations to study the asteroidal and cometary contribution to the water and organic budget of Mercury and Mars. We found that asteroids and comets deliver non negligible amounts of organics to Mars and this material will be deposited locally, close to crater centres. We also found that asteroids and comets together with dust particles can deliver the observational lower limits of water ice on Mercury. Interestingly, our own Solar System is not the only place that harbours minor bodies. About 20 stars are known to hold analogues of the Main Asteroid Belt and the Kuiper Belt. The role of the minor bodies, originating from those belts, in the delivery of material to exoplanets is unknown. To shed light on these delivery processes we extrapolate our Solar System scenarios to the exoplanetary system HR~8799. We found that minor bodies from both belts are colliding with the four giant planets of the system, which leads to water, organic, mineral and metal enrichment of the planets that may be observable.