He was just a teenager when the Viking Lander touched down on Mars, but now Sam Thurman is in charge of what could be NASA's fourth successful landing on the red planet.
In 1976, Thurman was miles from civilization, in the Colorado woods as a counselor at Boy Scout camp. But that didn't stop him from following the Viking mission.
"I remember asking guys on the staff who had radios to listen to the local station in Denver periodically," Thurman said.
"I remember early one morning stomping over the hill from my tent toward the mess hall. And somebody came running up the hill and said, 'The Viking 1 lander is down safely!' And I thought, 'Wow.'"
Thurman's interest in space exploration had been sparked even earlier, during the Apollo moon landings. But it was Viking that put him on a path to Mars.
"I realized, if you want to do planetary exploration, you better start learning about robotic spacecraft," he said.
A short time later, when Thurman got a look at a press kit on the Viking mission, he realized how challenging that job would be. "I thought, boy, this is real complicated," Thurman said during a recent interview. "Nothing's changed in that department. It still is."
Thurman knows this from direct experience -- he was on the successful Mars Pathfinder team and the unsuccessful Mars Climate Orbiter team. The latter craft was lost at Mars on Sept. 23.
Thurman helped to develop the landing system for Pathfinder, which bounced down to Mars on airbags in 1997. But unlike Pathfinder, Mars Polar Lander is a direct descendent of Viking and will make a final descent to the martian surface using retrorockets for a three-legged soft landing.
MPL designers also borrowed heavily from Viking hardware, especially the heat shield and the parachute. But the similarities end there.
For one thing, Viking's engines, which could be throttled to vary their power, have been replaced with thrusters that achieve the same effect by firing pulses in rapid succession. (Thurman explains, "Imagine that your car had a throttle with two positions, on and off.")
Just as important, 25 years of advances in microelectronics have given Thurman and his colleagues some real advantages over their Viking predecessors.
That's especially true of the Polar Lander's computer, which is far more powerful than its Viking counterpart. All of which makes Thurman appreciate even more what Viking's creators accomplished using early-1970s technology.
The job of building Mars landers hasn't gotten easier since Viking, but for Thurman, the biggest hurdles on the Mars Polar Lander haven't been technical. Like his colleagues, he has felt the stress of working on a space mission, which can take a toll on family life.
Harder still, though, was the loss of the Mars Climate Oribter. Now, Thurman says, the loss of MCO "has upped the stakes on this mission, which was already high-stakes to begin with. It's been tough."
Still, Thurman said, "We all want to be here, even though this is a technically and psychologically difficult mission. Everybody is here because they want to be."
Thurman was buoyed by the clean bill of health Polar Lander received recently after intense scrutiny by review teams at Jet Propulsion Laboratory. But it won't be until Polar Lander is safely on Mars that Thurman will be able to savor the accomplishment of following in Viking's "footsteps".
"Right now," Thurman says, "I've got my heart in my mouth, and we're working our tails off to make sure we get a safe landing."
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