The InSight mission will investigate the internal structure of Mars and the processes at play inside the planet to acquire a better understanding of the formation and evolution of earth-like planets. Similar to the other terrestrial planets – Mercury, Venus, Earth and the Moon – Mars has a metallic core surrounded by a rocky mantle, over which lies a rocky crust. According to model calculations, the core has a temperature of about 1900 degrees Celsius and could still be molten if it contains a significant amount of sulphur. This is one of the questions that the InSight mission will address. The mission will also conduct a study of seismic activity and measure the meteorite impact rate on Mars.