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Mercury, July/August 2003 Table of Contents

Courtesy of Dan Maas (Maas Digital LLC).

by Jim Bell

A planetary scientist recounts the long struggle to build and launch two rovers to Mars.

As the singer Elton John once said, "Mars ain't the kind of place to raise your kids." In addition to frigid temperatures, the atmosphere is stratospherically thin and composed almost entirely of carbon dioxide. Even summers are cold, with temperatures barely above freezing on the warmest days in the tropics. Winters are long and even colder — so cold that nearly a quarter of the atmosphere literally snows out onto the surface.

So why the big hoopla about exploring a place that makes Antarctica seem like paradise? The reason is simple: Mars wasn’t always this way. Centuries of telescopic observations and nearly 40 years of spacecraft flybys, orbiters, and landers have provided compelling evidence that Mars was once much more Earthlike than it is today. The evidence is preserved in ancient landforms reminiscent of riverbeds, flood channels, and other indicators of sedimentation and erosion. Atmospheric isotopic ratios suggest that the air was substantially thicker and warmer in the past. Finally, geological and mineralogical signatures point to long-standing bodies of liquid water at or near the surface — perhaps even relatively recently. Earth and Venus have long been referred to as sister worlds, but the real family resemblance appears to be with our little brother, Mars.

It is against this backdrop that NASA and other space agencies have framed their Mars exploration strategies. Big flagship missions like Mariner 9 and the Viking orbiters and landers provided most of our initial close-up views of the Red Planet. But more recently, especially in an era of tighter government space mission budgets, smaller missions like the Mars Pathfinder lander/rover and the Mars Global Surveyor and Mars Odyssey orbiters have provided (and in the case of the orbiters, continue to provide) exciting new information about the Martian past and present. These smaller missions are part of NASA’s ongoing "faster, better, cheaper" plan for solar system exploration, and despite the failures of Mars Climate Orbiter and Mars Polar Lander, the strategy appears to be working reasonably well.

NASA is putting control of many of these missions directly in the hands of scientists, which cuts bureaucracy and cost while maximizing scientific return. This grassroots philosophy has been used for the last two Mars lander/rover opportunities, Mars Pathfinder and the Mars Exploration Rover Mission, or MER, and it’s likely to be the model for future robotic surface missions planned for 2007 and possibly 2009.

I have been fortunate enough to have been involved for 8 years on MER. As this issue was going to press, our team was scheduled to launch two rovers to Mars no earlier than June 8 and June 25, and they will touch down on January 4 and 25, 2004. The twin rovers will explore separate landing sites for 3 months each. The story of how MER came to fruition is full of fascination and frustration, false starts and sudden endings, and many moments of wonder and excitement. Here's how it goes.