Maybe ever since the Moon landing, it's been pretty easy to overestimate the success of our space programs—when we want to go somewhere or launch something, we just do it, right? In actuality, space exploration remains a high risk endeavor, as the various Space Shuttle disasters have proven. And going to Mars? Maybe it's out closest planet, but going there isn't as easy as it seems.
To prove it, here's a clever graph of all the missions ever sent to Mars. As you can see, it's basically a bar graph; missions to Mars as listed chronologically, and the mission result is coded by how close the corresponding bar reaches to Mars.
As you can see, we should be seeing a blitz of new Mars activity in the next couple of year (though the Russian Phobos-Grunt expedition, originally scheduled for this month, has been pushed back to 2011).
Full-size version at We Love Data Viz, but here's a smaller one, to give you a feel for the entire poster: