On 5 May, the NASA “InSight”-lander set off on its journey to Mars. This is the first mission dedicated to investigate the internal structure of the red planet and to answer some key questions such as: Why have Earth and Mars developed so differently although their original structure and chemical composition seem so similar? How large, thick and dense are the core, mantle and crust? What is their structure? The scientists are hoping to gain fundamental insights into the general formation of rocky planets such as Mars, Earth, Mercury and Venus.