But that average masks a wide disparity in success rates among the four.
With the apparent failure of Phobos-Grunt, Russia is 0 for 17 attempts since 1960 at a mix of Mars flybys, orbiters, and landers.
Japan, which launched a Mars orbiter in 1998, is 0 for 1. Europe, with its inaugural Mars Express/Beagle 2 orbiter-lander combo, is 0.5 for 1 at the red planet. Launched in 2003, the duo reached Mars. The orbiter has been a science success, and its mission has been extended to 2014. But the lander was declared lost after repeated attempts to contact it failed following its December 2003 descent to the surface.
NASA, meanwhile, has enjoyed 11 successful Mars missions out of 16 launched since 1964, including flybys, orbiters, and rovers.
It's easy to get used to those successes, but they are far from assured.
Designing craft for interplanetary travel means tailoring its systems to function for years in an environment far different from the conditions craft encounter in Earth orbit, where designers have far more experience, Dr. McNutt says.
Flitting between Earth and anywhere else exposes a craft and its sensitive electronics to the potentially disruptive effects of cosmic rays.
Pick your destination and you will encounter much different contrasts in temperatures the craft must endure, compared with conditions at Earth. Think the Voyager spacecraft at the far edges of the solar system versus the Messenger mission orbiting Mercury.
Indeed, the combination of the vacuum of space and temperature can be a mission-ender, he says, citing NASA's Mariner 3 mission as an example.
Launched in 1964, it was the US's first attempt at a Mars flyby. But the craft ultimately failed, felled by the combined effects of vacuum and temperature – something for which it was not tested prior to launch. Engineers conducted vacuum and temperature tests separately.
The failure led to the development of test chambers that could replicate both conditions simultaneously, McNutt says.