Many of the design outputs of the NASA rover programs are public domain. For example, the peak solar panel rating of the MER (Opportunity and Spirit) is publish

Many of the design outputs of the NASA rover programs are public domain. For example, the peak solar panel rating of the MER (Opportunity and Spirit) is published, the size of the panels are known (or can easily by estimated), the power needed to drive the rovers around is published, the weight of the rover is published, the size of wheels can be easily estimated (or is published). The logistics of sending data back can be reasonably considered to be a challenge that could be solved on the first try. The first space probe that NASA managed to actually get to Mars (Mariner) worked. The first landers that NASA managed to get to Mars (Viking) worked.