writes "One European mission is on its way to Mars and two US landers will soon launch. They face tough odds for success. Of 34 Mars missions since the start of the space age, 20 have failed. This article looks at why Mars is so hard. It reports, for example, that a former manager on the Mars Pathfinder project believes that "Software is the number one problem". He says that since the mid-70s "software hasnâ(TM)t gone anywhere. There isnâ(TM)t a project that gets their software done.""
Or maybe it has to do with being an incredible distance, on an inhumane climate. Either or.