40 missions to Mars and 2/3 of them failed to even successfully land or begin their mission. Some even missed the planet entirely.
What are the odds for Curiosity surviving its landing Sunday night? Best (And Worst) Mars Landings Ever | Red Planet & Mars Exploration | Mars Missions, Mars Probes | Space.com
Soviet Union successfully landed Mars 3 on the surface Dec. 2, 1972. If you can call 20 seconds of communication and then nothing a success. I don't.
Mars dust storm, minor wobble give Curiosity scientists pause - latimes.com