On the Fourth of July 20 Years Ago, NASA Landed the First Rover on Mars

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The Pathfinder rover, Sojourner, is shown snuggled against a rock nicknamed Moe. The south peak of two hills, known as Twin Peaks, can be seen on the horizon. The rocky surface is comprised of materials washed down from the highlands and deposited in this ancient outflow channel by a catastrophic flood. (NASA/JPL)

On July 4th, 1997 as Americans were stoking their barbecues, a NASA spacecraft touched down on Mars and bounced like a beach ball. The Pathfinder mission was an unlikely and stunning success that marked the beginning of a roaming robotic presence on the red planet.

The successful feat surprised everyone—including the team behind the mission, a mission that didn’t have the best reputation in the beginning.

Jennifer Trosper applied to work at NASA in the nineties. “And I got a phone call,” Trosper says. “He [the recruiter] said, ‘Well, we got this project out here. Nobody really wants to work on it, because nobody thinks it’s going to work.’”

NASA was trying something new: space travel for a bargain price. Pathfinder’s mantra was cheaper, faster, better. The goal was to cut down on red tape and dream of solutions no one had else had thought of.

“Be crazy and bold and innovative,” says Pathfinder’s chief engineer Rob Manning.


'Cheaper, Faster, Better'

When Trosper arrived in Los Angeles, she joined a team of scrappy aerospace engineers at the Jet Propulsion Laboratory (JPL) willing to work on a lean budget and try something revolutionary.

“We didn’t follow all the rules. We had some good leadership, but it was a very small team," Trosper says, "And we were landing on the surface of Mars with air bags!”

The airbags were designed to cushion Pathfinder’s landing. Touching down on Mars can be tricky because the atmosphere is so thin. That’s one reason no other country had had a successful landing for twenty years. NASA's last success was the Viking 1 and Viking 2 orbiter-lander in 1975.

Low Budget Inspires Innovation

Manning says the team settled on a parachute to slow the spacecraft down as it hurtled through the Martian atmosphere. The engineers also wrapped the machine in a cocoon to protect it when it touched down on the rocky landscape—kind of like a beach ball.

Manning says the idea was that the ball “would bounce and roll on the surface. And finally open up like a flower and have a little rover drive off.”

If successful, the tiny rover—about the size of a microwave—would become the first wheeled vehicle to explore the surface of another planet. NASA named it Sojourner.

Seven months after the launch, NASA engineers monitored the spacecraft's status as it neared its icy destination. A nervous tension filled the control room at JPL. And then at the exact moment Pathfinder was expected to bounce down, a faint signal sounded, back on Earth. The room erupted with loud applause and cheering.

“By late afternoon for us we were getting our first picture,” Manning says, smiling.

Miraculously, Pathfinder had traveled millions of miles and landed upright on the red planet.

The Sojourner Rover at the Yogi rock on Mars. (Mars Pathfinder Project )

NASA uploaded the images to a new realm known as the World Wide Web. Jon Brooks, a science editor at KQED, remembers the moment vividly.

“You could see a little more, a little more, a little more," Brooks says, "and the anticipation was truly great because you were going to catch a glimpse of Mars for the first time. You actually saw the barren landscape and the red color.”

The Most Important Question

Sojourner was expected to take pictures for one week before its batteries died. Instead, the little spacecraft weathered the frigid climate for nearly three months. Pathfinder beamed thousands of pictures back to Earth, says Manning, to help his team answer one central question:

“Was Mars at some point in its past a place with lakes and an atmosphere and places where presumably life could actually get started?”

The quest to find an answer has inspired three more NASA rovers after Pathfinder. The latest, Curiosity, is the size of an SUV and has been driving around Mars for nearly five years looking for clues about how and when the red planet went from warm and wet to cold and dry.

Astronomers are still searching for signs of life, but they have confirmed the presence of water. Observations suggest that habitable lakes and streams likely existed in the ancient past.

“Doesn’t say anything about whether there was life there,” Manning says. “But it does say this planet is much more interesting than we ever dreamed.”

Mars is the only planet inhabited solely by robots (as far as we know). Next year the U.S. will send the InSight lander to Mars, and the Mars 2020 will follow. NASA hopes to land a human on the red planet within the next twenty years.