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NASA’s twin Mars Exploration Rovers are two of the most complex science spacecraft ever developed. (credit: NASA)

Why is Mars so hard?

This June will see the beginning of the most ambitious exploration of the Red Planet in a quarter-century. If all goes well, three launch vehicles—one Soyuz and two Delta—will lift off this month, placing four spacecraft on trajectories that will bring them to Mars by this December and January. Those spacecraft include the first European Mars orbiter, Mars Express; Beagle 2, the British lander built with a mix of public and private funding; and NASA’s twin Mars Exploration Rovers, perhaps the most advanced Mars spacecraft even built. They will be joined at Mars by Nozomi, a Japanese-built Mars mission launched in 1998 and forced to take the long road to Mars because of thruster problems.

This should be an exciting time for those interested in Mars exploration, and for scientists and activists alike, it is. If these missions are successful, they should offer new insights about what happened to the planet’s water and the potential for past or even present life there: some of the most important questions in planetary science and astrobiology today.

The catch is, if these missions are successful. The history of robotic exploration of Mars, stretching back more than four decades, is littered with failed missions and dashed hopes. Some of these failures can be chalked up to the growing pains of early planetary exploration, when a wide variety of spacecraft of all types failed. Others, particularly the 1999 failures of NASA’s Mars Climate Orbiter (MCO) and Mars Polar Lander (MPL), are more indicative of management, programmatic, and other problems, rather than purely technical issues. Understanding these problems, and acting to correct them, are critical if current and future missions are to succeed in studying the Red Planet.

The star-crossed history of Martian exploration

Mars has been one of the most popular destinations for missions beyond the Earth. Since 1960 the United States and the former Soviet Union have launched 34 missions to Mars: 15 by the US and 19 by Russia and the former USSR. NASA’s success rate is not too bad: nine of those 15 missions, including the Mars Global Surveyor and 2001 Mars Odyssey missions still in progress, can be considered successes. Russia’s luck has not been nearly as good: 14 of its 19 missions failed, and only one—Zond 3—can be considered a complete success; the remaining four are, at best, partial successes. Overall 20 of the 34 American and Russian Mars missions, or 59 percent, failed.

Four of the seven NASA Mars missions since Viking—Mars Observer, MCO, MPL, and Deep Space 2—have failed.

Digging into those statistics in greater detail shows some interesting—and troubling—trends. Many of the failed missions, particularly those launched in the 1960s, were lost because of launch vehicle failures, not because of any fault with the spacecraft itself. Many Russian spacecraft, from the earliest “Marsnik” missions of 1960 to Mars 96, either failed to leave a parking orbit around the Earth or never made it into Earth orbit into the first place. However, in the last 30 years only one mission out of 16 attempted—Mars 96—was lost due to a launch vehicle malfunction. This can be most likely attributed to the maturity of launch vehicle development, including the use today of vehicles whose designs date back literally decades.

The problem with Mars exploration now appears to be with spacecraft themselves. Four of the seven NASA Mars missions flown since the twin Viking missions—Mars Observer, MCO, MPL, and Deep Space 2—have failed, all due to spacecraft problems of one manner or another. (MCO is a borderline case, since there was no technical problem with the spacecraft itself, but rather with how ground controllers operated it.) The only other NASA Mars missions to fail, Mariner 3 in 1964 and Mariner 8 in 1971, were each lost due to launch vehicle malfunctions. While getting spacecraft to Mars has become easier over time, making sure the spacecraft operate successfully has, perversely, gotten harder.

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