A statistics from a few years ago:<p><a href="http://www.popsci.com/science/article/2012-08/mars-rover-curiosity%E2%80%99s-biggest-challenge-mars-itself" rel="nofollow">http://www.popsci.com/science/article/2012-08/mars-rover-cur...</a><p>"In the decades since humans started sending spacecraft to Mars, the Red Planet has outscored us handily; humans have only about a .411 batting average overall -- not great for missions that cost billions of dollars and countless time to build. Seventeen landers have been sent, and just seven made it to the surface safely, each of them with varying degrees of success."<p>Afterwards, Curiosity rover luckily succeeded, under much harder constraints then these now (being huge but sensitive), so that is at least 8 from 18. With this one, 8 from 19 (giving, interestingly, 0.42). I don't know which the real ratio now is, am I missing something?
I especially liked this sentence:
> the module had successfully completed most steps of its 6-minute descent through the martian atmosphere<p>Completing "most steps" in a landing, but not the last one (I.e. Safe touchdown) is equal to a crash.