Another July 4th Anniversary: Pathfinder's Landing On Mars

Jul 3, 2017
Originally published on July 5, 2017 6:04 am

Twenty years ago Tuesday, a plucky little probe named Pathfinder landed at Ares Vallis on the surface of Mars.

It didn't land in the traditional way, with retrorockets firing until it reached the surface. No, Pathfinder bounced down to its landing site, cushioned by giant air bags. It was a novel approach, and the successful maneuver paved the way for a similar system used by the twin rovers Spirit and Opportunity in 2003.

I was at NASA's Jet Propulsion Laboratory on landing day. JPL is the home of mission control for most of NASA's planetary missions. Prior to the landing at 10 a.m. PT, engineers nervously watched their consoles, even though there was really nothing they could do if there was a problem. It takes several minutes for a radio signal from Mars to reach Earth, so the landing sequence was already well underway when the first signals reached Earth.

I had spent a lot of time before landing day getting to know the scientists and engineers involved in the mission. I didn't talk to all of them, but it was a relatively small team, and I spoke with a lot of them. I knew well how hard they had worked on the mission, and how many things had to go just right to make it a success. I knew they had good reason to be apprehensive.

But the landing went flawlessly, and I witnessed anxiety turning into unbridled joy. That day is one of the highlights of my career in science journalism.

At a news conference after the successful landing, mission scientist Matthew Golombek was gushing.

"We have basically the perfect site," he said. "We have the perfect spacecraft. We have the perfect instruments. And we have the perfect rover. And now we're just more excited than you could possibly believe to go out there and start to investigate what's there."

The rover Golombek was talking about was called Sojourner, a pint-size version of the larger rovers NASA has subsequently sent to Mars. Sojourner lasted 83 days and traveled a whopping 100 yards.

Before they went silent, the lander and rover sent back a total of more than 17,000 pictures. The mission didn't exactly rewrite the textbooks about Mars, but the images and data from the probe's scientific instruments suggested that once upon a time the Red Planet was warm and wet, quite the opposite of the cold, dry place we see today.

On this 20th anniversary of the Pathfinder landing, I'd also like to take a moment to correct a misleading statement we made two decades ago on All Things Considered. In the introduction to a chat between me and host Robert Siegel, we said the following:

"After traveling for seven months and more than 300 miles, the U.S. spacecraft Pathfinder landed on Mars today."

Although strictly speaking that's true, I meant to write "300 million miles." I don't suppose too many people think Mars and Earth are only 300 miles apart, but I didn't mean to give the impression that I was one of them. I have felt bad about that ever since. It didn't help that a few years later, NPR decided to put a transcript from one of our shows on all of its business envelopes, and wouldn't you know, they chose the transcript with that misleading statement in it.

So mea culpa.

OK, I feel much better having gotten that off my chest.

Happy anniversary, Pathfinder.

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Twenty years ago tomorrow, a plucky little NASA probe called Pathfinder landed on Mars. Actually, it didn't so much land as bounce down to the surface. Its final descent was cushioned by giant airbags. Pathfinder carried with it a pint-sized, six-wheeled rover called Sojourner. NPR science correspondent Joe Palca was at Mission Control at NASA's Jet Propulsion Laboratory on landing day. He spoke with me then and he's back with me now. You're still here. Hi, Joe.

JOE PALCA, BYLINE: Yeah, I can't get away. No, it was an amazing day.

SIEGEL: Pathfinder wasn't the first NASA spacecraft to land on Mars. It wasn't the last. What was so important about this one?

PALCA: Well, it had been a long dry spell. It had been 21 years since NASA had landed a serious spacecraft or a serious probe on Mars. And there was a lot of excitement. This airbag landing system was, like, pretty wacky. The thing came in at 30 miles an hour and bounced 50 feet in the air. Fifteen times it bouncy, bouncy, bouncy before it came to rest and opened itself up and then spread out its petals, which had solar panels in them.

SIEGEL: After it got to work, what were the most exciting things that we learned about Mars thanks to Pathfinder?

PALCA: Well, it landed in a place where water seemed to have once flowed. And the kinds of rocks it was seeing and some of the chemical composition that it detected seemed to suggest that Mars was once a warmer, wetter place, as opposed to the dry, cold place it is today.

SIEGEL: Back in 1997, you were at the Jet Propulsion Lab in Pasadena, Calif., when Pathfinder touched down on Mars. Remind us what it was like that day.

PALCA: Well, it was so intensely exciting because this mission was a smallish mission. I mean, it was put together in three years. I don't remember the exact number - $265 million, you know, chump change for a space mission. And so I - all the people who worked on it, it was like they had built it in a garage and taken it down to Kennedy Space Center and launched it into space. And it had - so it had that sort of, wow, is this really going to work quality to it. And when it did, you just cannot believe the excitement that the scientists and engineers felt. And there's a clip here from Matt Golombek, Matthew Golombek, who was the lead scientist. And it captures that exactly.


MATTHEW GOLOMBEK: We have basically the perfect site. We have the perfect spacecraft. We have the perfect instruments. And we have the perfect rover. And now we're just more excited than you could possibly believe to go out there and start to investigate what's there.

SIEGEL: And 20 years after all that, where are we when it comes to Mars exploration?

PALCA: Well, Pathfinder set the path for the two rovers that came next in 2003, Spirit and Opportunity. They used air bags. Curiosity, which landed a few years ago, didn't because it was too big. So the days of airbags seem to be gone. But there's another mission to be launched next year that's going to measure the geophysics of the planet and a couple more in 2020. So NASA and ESA, the European Space Agency, everybody loves Mars.

SIEGEL: Now, there's something that you've been embarrassed about for 20 years.


SIEGEL: And I ought to be equally embarrassed, but for some reason less so. I read in the introduction to our conversation on that July Fourth a number of how far Pathfinder had traveled that had been supplied by you...

PALCA: That's right.

SIEGEL: ...And edited by the NPR Science Unit and gotten past my editor here.


SIEGEL: And I applied not full brain power and read it. I said that this - it had gone farther than New York City is from Washington, D.C...

PALCA: That's right. You said...

SIEGEL: ...Three hundred miles.

PALCA: That's right. You said it had traveled for seven months and more than 300 miles.


PALCA: And of course, we left off the million.

SIEGEL: It had gone more than 300 miles, though.

PALCA: We were - strictly speaking we were right. But it does leave a measure of...


PALCA: ...What shall I say - misleading people. I mean - and I don't - I mean, I'm sure most people know that Mars is further than 300 miles away. But I didn't want people to think that I thought or you thought it was something like 300 miles away. And that's been - I've felt bad about that for 20 years. So I really - I really appreciate you giving me a chance...


PALCA: ...To rectify that. Oh, you know, who says you get another chance? But you get another chance.

SIEGEL: Joe Palca. Thanks for talking with us.

PALCA: You're welcome. Transcript provided by NPR, Copyright NPR.