Mars mission development is typically undertaken to fill a gap in knowledge about the Red Planet because an orbiter or lander spacecraft return data to gain new understanding. At the start of the space age, research questions were put forward to enhance our Mars understanding. However, they were wide in scope. In this sense, two early examples were confirming at a broad scale the composition of the planet’s atmosphere and the imaging of surface features at a better resolution rather than the previous telescopic observations. In addition, early missions, being constrained by technology available at the time were able to provide huge order-of-magnitude increases in understanding of Mars with relatively rudimentary instruments (Chap.  1 ). Over the following decades, as more missions returned data, scientific questions have become much more refined, requiring more tailored engineering designs to answer them.