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Season 3, Episode 10: A Voyager’s View of Earth

Season 3Episode 10Dec 22, 2020

The Voyager 1 spacecraft has traveled farther away from Earth than any human-made object. Candy Hansen and David Grinspoon talk about the Voyager mission, and its humbling perspective of our planet as a tiny blue dot in the blackness of space.

On a mission logo

On a mission logo


(Voyager Golden Record greetings)
: “Hello everybody”Hindi: “Greetings from the inhabitants of this world.”Hebrew: “Peace.”

[0:08] Narrator: The Voyager 1 and Voyager 2 spacecraft left our planet 43 years ago, and they both carry something unique, something no other spacecraft has ever had. Affixed to their sides is a phonograph record, made of copper and coated in gold to keep it from interfering with spacecraft electronics.

The identical Golden Records contain greetings from Earth in 55 languages, from Arabic:

(Voyager Golden Record greetings: Arabic)

“Greetings to our friends in the stars. We wish that we will meet you someday.”

(Voyager Golden Record greetings: Zulu)

To Zulu: “We greet you, great ones. We wish you longevity.”

The reason to send greetings in so many languages was not to confuse potential extraterrestrials who might play the record someday, but instead, to have a diverse chorus that represents a broad sphere of humanity.

[1:10] The Golden Records also feature the songs of birds and humpback whales, and also crickets, frogs, a chimpanzee, a dog. There are sounds made by our planet, like volcanoes, earthquakes, thunder, and ocean surf. There are sounds of our vehicles, including a train, a plane, an automobile, and the lift-off of a Saturn V rocket. There are more personal human sounds like footsteps, a heartbeat, and a mother caring for her baby.

(note: sound effects follow each description)

[2:14] The Golden Records encoded more than 100 photographs depicting different scenes of Earth and its inhabitants. And of course, no record would be complete without music.

(Voyager Golden Record music: “Queen of the Night aria from Mozart’s “Magic Flute”)

Narrator: There’s Mozart’s Magic Flute. A Peruvian wedding song.

(Voyager Golden Record music: Wedding Song – Peru)

Narrator: Songs from Aboriginal Australia

(Voyager Golden Record music: “Morning Star and Devil Bird” – Australia)

Narrator: And, perhaps most famously, “Johnny B. Goode” by Chuck Berry.

(Voyager Golden Record music: “Johnny B. Goode” by Chuck Berry)

[3:04] Chuck Berry performed this song at NASA’s Jet Propulsion Laboratory in 1989, to celebrate Voyager 2 reaching the planet Neptune. Among those dancing along to the music was the astronomer Carl Sagan.

Carl was one of the scientists on the Voyager mission, which had been built and tested at JPL. The original goal of the mission had been to fly the two spacecraft past the gas giant planets Jupiter and Saturn, collecting images and information about them and their moons. The spacecraft were built to last 5 years, but if they could last even longer, the outer planets Uranus and Neptune were also within reach.

Normally visiting all those planets would be beyond the capabilities of most spacecraft, because of all the fuel and time needed to ping-pong around the solar system to intersect with each of the planets in their distant orbits around the Sun.

[4:09] But JPL engineer Gary Flandro figured out that during the 1980s, the outer planets would all line up on the same side of the Sun. This planetary alignment wouldn’t happen again for 176 years.

It would take several years for a spacecraft just to reach Jupiter, so Voyager 2 left Earth on August 20, 1977, and Voyager 1 followed a few days later, on September 5. Even though it launched after Voyager 2, Voyager 1 was on a shorter and faster route to Jupiter, and so would reach that planet first.

After the Voyagers completed their planetary tours, they would keep flying on, eventually leaving the solar system to head out into the galaxy. Carl reasoned, why not use this opportunity to also send a message to the stars, a shout of solidarity with our fellow space wanderers?

[5:11] This was a new variation on an earlier theme. The Pioneer 10 spacecraft, launched in 1972 for a Jupiter flyby, was the first NASA mission sent on a path that would eventually take it out of the solar system. It was quickly followed in 1973 by Pioneer 11, which visited both Jupiter and Saturn before heading outwards. Carl had helped ensure each of these future interstellar wanderers sported gold-plated plaques etched with drawings about Earth and humanity. The Voyagers would be going even faster than the Pioneers, and thus travel farther, and recorded messages could convey so much more.

(Voyager Golden Record music: Pygmy Girls Initiation Song, Zaire)

[5:59] The Golden Records may be forever silent, never to encounter other life in the galaxy. But if, by remote chance, one of the records finds itself speaking to an audience on some strange and distant shore, among the many voices of this alien world called Earth, they’ll hear one of Carl’s children. That message perhaps best sums up this auditory time capsule, regardless of your age.

(Voyager record greetings:“Hello from the children of planet Earth.”)

(Intro music and NASA montage)

[7:04] Narrator: Welcome to “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory. I’m Leslie Mullen, and in this third season, we’ve been following scientists to the ends of the Earth as they explore the many aspects of our home planet.

In the first episode of the season, we pulled back from Earth to see it from an astronaut’s perspective. In this final episode, we’ll gaze upon our planet from an even greater distance, the farthest any human-made object has ever traveled. This is episode 10: A Voyager’s View of Earth.

(NASA audio/Apollo 11)
Neil Armstrong:
“That’s one small step for (a) man, one giant leap for mankind”

Narrator: Like most space scientists who grew up in the 1960s, David Grinspoon was inspired by humanity’s first steps on the Moon during NASA’s Apollo 11 mission. But his household had an extra source of inspiration.

[8:01] David Grinspoon:I have this very specific memory, really my earliest vivid memory, of watching the Moon landing on TV late at night on the little scratchy black and white signal when I was in the fourth grade.

(NASA audio/Apollo 11)
Neil Armstrong:
“…but it’s adequate to get back up…” (beep)

David Grinspoon:And that blew my mind and help set me on the path I’m on. But in some ways, I had a kind of unusual childhood too, in that my dad’s best friend was Carl Sagan. And he was around our house a lot, and this was before he was famous.


David Grinspoon:My dad was a psychiatrist at Harvard, and he and Carl Sagan became really close friends in the mid-sixties because they were two of the Harvard faculty who were opposed to the Vietnam War, before it was popular to be opposed to the Vietnam War.

[9:00] So I had this guy, Uncle Carl, who was very much in my life when I was a kid, who was involved in some of the early space missions. And he’d show up at the house with an 8 by 10 glossy photograph from Mariner 9. And this was way before the internet when you could just download these things. And as a kid who had already been sparked by Apollo, that was amazing.

And I was very into science fiction and “2001: A Space Odyssey” was coming up and we were going to be going out to Jupiter and, you know, all that fiction and real science was all mixed up in my mind as this excitement about the future and excitement about exploring space.

And kind of also part of this utopian vision of humans solving problems and using science to create a better world. The vision of humans expanding into the Universe was mixed with the visions of humans being more enlightened, and there was a sort of utopian idea that we would become, you know, Homo cosmicus, the cosmic connection, where we would become star folk. (laughs)


[10:10] David Grinspoon: I was definitely a teenage space geek, and my friends and I were part of something called the L5 society, where we thought we were all going to go live in cylinders in orbit designed by our other hero, Gerard O’Neill, who was this Princeton physicist who wrote this book called “The High Frontier,” and had this idea about space colonies. And they were going to be at the L5 point, which is the stable orbit point between the Earth and the Moon. And in high school, in the seventies, we had these buttons that said “L5 in 95.” Because we were convinced that by the 1990s, we’d be living in orbit. (laughs)

Narrator:David pursued his utopian vision for the future by studying planetary science at Brown University in Rhode Island. Some of his professors were working on NASA’s Viking Mars landers, and before long, David found himself at Mission Control.

[11:01] David Grinspoon:There was this magic land out in California; this place called JPL where all this incredible stuff happened, all these space missions. My first time out at JPL was during the Viking 2 landing on Mars in 1976.


David Grinspoon:I got to go out and stay in Pasadena with Carl Sagan and his son Dorion, who was my best friend. And the Viking 2 landing was incredibly exciting. When those first pictures came down, you know, the way the Viking cameras worked is it came in stripe by stripe. So you see this one little row, that doesn’t really make sense, of pixels, and then the next row, you could start to see all those rocks and those are dunes and you see the image assemble itself slowly in real time as it comes down.

Narrator:David returned to JPL three years later, this time to work as a student intern for the Voyager mission. Voyager 1 was nearing Jupiter, and Carl was on the imaging team responsible for taking photos of the planet and its many moons.

[12:06] David Grinspoon:That was just an amazing experience, being part of Voyager as a student and showing up and seeing all these scientists at work, running the spacecraft that was encountering the Jupiter system up close for the first time. And all these scientists that seemed like gods to me, and they still do, kind of. Not just Carl Sagan, but people like Andy Ingersoll and Gene Shoemaker and Candy Hansen. I could go on listing names, but all these people that were like, wow, these are the real deal. These are planetary scientists. I’m watching them explore planets and I’m helping them doing my little menial clerical tasks.

Although, Carl gave me a real research task that summer that was really hard. It had to do with the solar spectrum in the ultraviolet, and representing it in a specific way that, in order to give him what he wanted, I had to work out some quantum mechanics that I didn’t really know.

[13:09] But I really wanted to do it well and impress him and impress the other scientists. So I ended up going to Caltech and getting into the Millikan library and reading some books and doing some calculations. I have no idea if I even did it right. I probably screwed it up, but it was like, “Wow, I’m doing science!” (laughs)

But mostly just being there and being a fly on the wall was exciting. You know, if you’re in that room, you’re with that small group of humans that are seeing it for the first time. And the other people in that room are the people that built the spacecraft to send out there. Just that sense of discovery, and the latest images would be on the monitors there in the area where the imaging team worked.

The thing about these encounters of the Voyagers, they happen really fast. The spacecraft is approaching for years and months and the planets and the moons are just these single pixel dots. And then a few days before the planet’s starting to get close enough, so you can see it as more than a dot, you can start to make it out as a round object. And then you can start to see detail on the planet and then on the moons.

[14:09] And it happens so fast, partly because the spacecraft is also accelerating as it’s pulled in by the gravity of Jupiter. But in a matter of days, it goes from being a dot to being these resolved objects.

And it felt like you were almost on the ship and looking out the window. You know, “It’s getting closer, it’s getting closer.” And you see it getting bigger and starting to reveal itself; that real-time sense of discovery, where it was almost like you were traveling with the spacecraft and seeing the Jupiter system go by.

(Voyager Golden Record music: “Tchakrulo,” by singers from Georgia)

Narrator: Each Voyager flyby revealed new details of the planets and their moons. They showed that Jupiter’s moon Io had volcanoes erupting lava hundreds of kilometers high into space. Jupiter’s frozen moon Europa had a strange cracked-ice surface that concealed a vast ocean below.

[15:07] The Voyagers examined the intricate woven threads of Saturn’s dusty rings, and saw that Saturn’s moon Titan was enveloped in a thick orange smog.

While Voyager 2 would go on to visit the cool blue gas giants Uranus and Neptune, Voyager 1’s path around Saturn sent it above the ecliptic, the disc-like region where the planets orbit the Sun, like a record spinning on a record player. From this point on, Voyager 1 would visit no more planets. Instead, all the planets would recede steadily from its view, once again becoming tiny points of light.

Carl wanted to maneuver Voyager 1 so that it could take photos of all those tiny dots, to create a family portrait of the planets of the solar system. But as imaging team member Candy Hansen explains, getting permission from NASA’s Voyager Project Office was no easy task.

[16:02] Candy Hansen:We asked for that picture a number of times, and the first time was in 1981. We asked in 1986 and we asked in 1988, and they just were never really willing to spend the resources.

There were two reasons that we were getting turned down. One was that every time we asked for it, it was either right after a flyby or right before a flyby, when they were either staffing up or staffing down, or in the middle where there was no staff. So there was always an issue with staffing. But there was always this feeling on the project that they didn’t want to pull out all the stops to get this observation, because they didn’t think it was that important.


Candy Hansen:The technical challenges had to do with pointing close to the Sun. And so there was always a concern, if we point too close to the Sun, then we might actually damage the camera, even that far away.

[17:04] And that may have been the reason that Carl waited until Voyager 1’s mission was essentially done in 1981. It was finished with its planetary exploration. And then it seemed like, “Okay, if we use Voyager 1, we’re not taking any risk for future flybys of Uranus and Neptune.” We wouldn’t want to damage the camera on Voyager 2 because it’s got work ahead of it. But it turned out that we actually used Voyager 1 quite a bit as a test bed for the things that we were going to do on Voyager 2. So people still did not want to take risks with the hardware, even if Voyager 1 didn’t really have a scientific need for it anymore.

But also, Voyager was what we call 3-axis stabilized. And what that means is that it had a fixed orientation. You held that fixed orientation with the Sun sensor knowing where the Sun was, and with a star sensor that we usually had parked on Canopus, because that’s the brightest star in the Southern Hemisphere.

[18:12] And so, in a way, the spacecraft was just rock steady in that orientation, and we knew it’s not going to overheat on one side or get too cold on the other. We knew those were stable orientations where kind of nothing could go wrong. So when you take it out of that well-understood configuration, what might go wrong? We took it off the star, will it be able to find it again?

And when we had to do maneuvers, which we actually had to do from time to time, every once in a while, we wouldn’t get the signal back. And everyone would panic, “Oh my God, we lost the spacecraft.” And then they would bring all the big antennas and next thing you know, you’d hear this little tiny whisper of a signal over the low-gain antenna, and everybody’d be like, “Oh, okay, okay, it’s okay.” And then we’d have to wait for it to do its star search till it finally found Canopus again. And then we’d get the big booming signal back again, but every time it was like, “Oh no, we lost Voyager!” (laughs)

[19:15] Narrator:The risk of turning Voyager 1 always outweighed the wish for a family portrait of the planets. After many requests were rejected over the years, time was running out – and not only because the planets were growing fainter in the distance.

Candy Hansen:In 1989, it was obvious that this was going to be our last chance. We knew that the project would be staffing down dramatically. The engineering expertise would be off working on other projects, and we knew we needed to start turning off the instruments because the spacecraft power level was dropping, and so we knew the cameras were going to be among the first instruments to be powered off.

[20:02] And so, there was this kind of band of advocates that were just like, “We’re not going to give up, we’ll just keep asking and keep coming up with ideas.” And Carl never gave up. I never gave up. Carolyn Porco and William Kosmann, they were part of our band of advocates. And then it was, like I said, the fact that we knew this is really our last chance. Carl went to headquarters, and there was a meeting here in Pasadena, and that was the meeting where they decided, “Okay, yes, the project will carry this out.”

But there was still a lot of, I don’t know, a lack of enthusiasm, I guess I would call it. So I kind of took it on myself to personally sell it. You know, tell people, “This is going to be great. Here’s why it’s going to be great. You’re going to love it.”


[20:59] Narrator: On February 14, 1990, Voyager 1 took 60 images of our solar system – the first time a spacecraft was far enough away to capture such a vast distance in a glance. On that Valentine’s Day, Voyager 1 was 3.7 billion miles away from the Sun, or 6 billion kilometers. Candy says the date of the photo session wasn’t deliberate.

Candy Hansen:It was a coincidence, but what a nice coincidence! It’s like Voyager’s Valentine to us.

The original idea that Carl had was to do a whole mosaic of the sky and get the whole stellar background. But the problem was, that was going to take far more images than we had space for on our tape recorder. And the exposure was too short to get stars. I think our cameras could get down to like 10th magnitude stars, but the Earth was brighter than that.

[21:58] And so we knew we wanted to do color of each of the planets, so that took up 18 images or however many it was. We would take the images through the different color filters, and then we would stack the different colors together and do color reconstruction. We had six or eight filters, but we didn’t have enough data volume to send all of them back all of the time. So we would typically pick out which ones sort of worked the best for different situations.

And then we did the wide-angle frames, the bigger ones. The narrow angle are the little ones that have the planets. And so, since we knew we couldn’t do the whole stellar background, we thought, “Well, we’ll just connect the dots.” And that’s why it’s that particular shape, and then we said, “We have a few left over, so let’s go around the Sun.” So this is the design process.

[22:56] Narrator: The photos that make up the solar system portrait are patched together in a long sinuous shape resembling a hobbyhorse, a toy horsehead with a stick protruding from beneath it for a child to ride on. For the Voyager mosaic, the head is made up of photos taken around the Sun — which includes Earth, Venus and Jupiter. Saturn and Uranus are in the body of the stick, and Neptune is at the bottom end. Mars and Mercury are not pictured – Mercury is too close to the Sun to be seen amid the bright glare, while the sunlight reflecting off Mars was too faint from the camera’s perspective.

After the last photo was taken, Voyager 1’s cameras were turned off, and it took more than two months for the spacecraft to send all the images back to Earth.

As expected, all the planets were mere dots, about a pixel in size or less. Earth’s pale blue dot was barely visible amid streaks of light emanating from the Sun. Carl Sagan famously said it looked as though our planet was a mote of dust suspended in a sunbeam.

[24:03] Candy Hansen:To this day, it still gives me shivers down my spine, that connection. That’s home. Voyager is way out there, and looking back at home, and that’s where we are.

You know, to see your home planet up close, it’s like, “There’s the ocean, there’s continents.” And the Pale Blue Dot is, “Take that perspective, but now move out to the outside, way outside.” And now you realize that that beautiful blue orb is this tiny little speck in space. And we’re alone out here, nobody’s going to come save us from ourselves.

(Voyager Golden Record music:Japan, shakuhachi, “Tsuru No Sugomori” (“Crane’s Nest,”) performed by Goro Yamaguchi)

Candy Hansen:I would say we need this image; we need to see how alone the Earth is in space, we need to see how far away any other planets are.

[25:04] If something goes awry here on planet Earth, we are not going to be able to move seven billion people to the Moon or to Mars. Those are not hospitable places, they’re not all that close, and so we really need to take care of our home planet.

And the thing that has really been amazing to me is to realize how timeless that message is, because when we planned that image, it was still the Cold War, and the United States and the Soviet Union had I don’t know how many thousands of nuclear warheads pointed at each other. And today, the existential threat is climate change. So Carl saw that picture as a way to communicate that we’re all in this together.

[26:05] Narrator: The creation of that far-distant image of our home planet bookends Candy’s journey with the Voyager mission, which began for her as a calculated maneuver to come back home to Los Angeles, where she’d grown up.

Candy Hansen:I had gone to Tucson to go to graduate school, but I was really homesick for California. And so, I talked my graduate school advisor, Brad Smith, into sending me to JPL for a summer, like an internship. And because my advisor was the leader of the Voyager imaging team, it was kind of natural for me to work for the imaging team.

Certainly, in my graduate courses, we were looking at images from space, and there’s certain things that you learn about the lighting, what’s good lighting, what’s not good. But mostly, honestly, it was an on-the-job learning experience. And that was okay, that was fine with me, I loved it. So I never did go back to Tucson. I did ultimately finish my PhD at UCLA.

[27:10] Narrator:While Candy was a student intern, she applied for a job with the Voyager mission, and later wrote her PhD dissertation using Voyager data. Since then, Candy has worked on other space missions like the Cassini mission to Saturn, the Mars Reconnaissance Orbiter, and the Juno mission to Jupiter. Her long career that started with Voyager is all the more remarkable considering Candy never intended to become a space scientist.

Candy Hansen:When I was around 12 or 13, I discovered the science fiction section of our local library, and I read every book on those shelves. But I never thought of it as a career. When I went to college, I was not planning to major in physics, I was planning to major in anthropology and accounting, because I had in mind I wanted to get a job in city government. I liked math, so that’s the accounting connection.

[28:08] My dad drove a bread truck for Oroweat and my mom was a housewife, so I didn’t get a lot of advice on what to do when I got to college. So I know today it sounds a little bit random, but I know I had a plan in my 18-year-old head. (laughs)

But what happened was, I needed to have some general education classes including a science class. And this was of course all pre-Internet, so you had to actually stand in line for hours to sign up for your classes at Cal State Fullerton. And so I was standing in line and I had the course catalog, and I was looking through trying to decide what my general education science class should be. And the guy standing next to me said, “Oh, I had that physics class, it was really good.” And it was basically, “Intro to Physics for the Non-Science Major.” And so I looked at it and I’m like, “Oh yeah, well, actually that would fit pretty well in my schedule.”

[29:05] But when I got into the class, I loved it. So when you really love something, you tend to excel at it. And it turns out that at that moment, the physics department was trying to beef up their student population, and so they were watching these general education science classes for people that they might be able to pull into the department and get them to change their major.

So my professor one day calls me aside and he said, “You seem to really like this class.” And I’m like, “Oh yeah, I’m really enjoying it.” He said, “What do you think about being a physics major?” He said, “All you have to do is sign here.” Because they had, unbeknownst to me, filled out all the paperwork (laughs). And so, I was thinking to myself, “Well, if it’s this easy to get into, it should be this easy to get out of again if I don’t like it.” So sure, signed my name.

[30:02] And then I really did like it, but I have to say at that point in time, it was the Vietnam War, and most of the jobs coming out of college with a bachelor’s degree in physics were doing things like weapons development and that sort of thing, and I didn’t want to do that, I knew that. And so, I was really flailing a little bit.

And one of my professors, Professor Wollum, had worked on the Apollo missions, on the surface-exposure experiments — the radiation, and what affect that had on materials in this harsh space environment. And she taught a class called, “Planetary Physics,” which I loved. And so she was the one who suggested that I might go to graduate school at the University of Arizona in Tucson, because the Lunar and Planetary Lab there was kind of a hotbed for this new field of planetary science.


[31:07] Candy Hansen:You know, before spacecraft, all planetary science was within the realm of astronomy. And it wasn’t until we really started flying spacecraft to these places that you could see the geology on the surface of Mars and know it’s a heavily-crated surface in many places. And so the field of geology expanded in that moment from being all about the Earth to, well, when we look at the Moon, when we look at Mars, when we look at Mercury, now we’ve got all these different instances of geology. And kind of the same thing, you know, with atmospheres. Meteorologists study storms on the Earth, but they also were starting to study storms on places like Jupiter.

[31:56] And so, the Voyager imaging team was this collection of people who were geologists who were used to looking for oil, and meteorologists who happened also to think that Jupiter was pretty darn interesting. But there were also astronomers who were used to looking at a point of light as it moved around the sky, and figuring out what you could tell about the surface from the way it was reflecting light. It was quite an interesting mix of scientists who had gone from looking at something on the Earth to looking at something in space. And so they were the first generation, really, of planetary scientists.

Narrator:The Voyager 1 images weren’t just a family portrait of the planets of the solar system. They also were a family portrait of the Voyager mission team, with each planet like a milestone in their lives.

Candy Hansen:When I was hired, there was kind of a flock of us 20-somethings that were all hired around the same time, and so we were all just out of college. So in those days we talked about who we were dating and what was the cool concert we had gone to.

[33:06] And then, as time went by, we bought cars, we bought houses, we got married and we had kids. And so at the end of that 12 years, in a person’s life, that’s where a lot of things happen, right? And we had all, as a group, kind of moved through it together, and all of us told time, in a sense, by the planets. So it was between Jupiter and Saturn that I bought a car, and it was between Saturn and Uranus that I bought a house.

So it was all very special and towards the end, very bittersweet. We learned a lot of really incredible things, a lot of astounding discoveries, but there was a heart to the project as well. We love those spacecraft. (laughs) I know you shouldn’t love an inanimate object like that, but they are extensions of ourselves.

[34:05] And so that Pale Blue Dot picture was a bit of a gift to ourselves. You know, we’re not just going to shut down and move away. We’re going to do one more cool thing before we call it quits.

I was on Voyager for maybe another six or nine months after that because we were just wrapping up and boxing things up, and outside the door of my office was a bookcase, and in the bookcase we had albums full of hard copy. And the day that they came and took that to the Regional Planetary Imaging Facility, and it was only a couple of floors down, but it was no longer there, outside my door. (laughs) I went home that day, I was just kind of devastated, you know? I had this blank wall outside my door.

But when we got the Pale Blue Dot images, we had a big blank wall there, and so we, like a bulletin board, just stuck them up, and made that little hobbyhorse shape out of it, and put it to good use.

[35:08] Narrator:In addition to a child’s toy, a “hobbyhorse” is a term meaning a favorite topic or preoccupation. The Voyager family portrait certainly has been a favorite part of the mission for many of the scientists who worked on it, and for the general public as well. For a while, that hobbyhorse was displayed across 20 feet of wall in JPL’s von Kármán auditorium, and visitors to JPL got to see the solar system spread out before them.


Candy Hansen:The person who was in charge of the von Kármán exhibits at that time was Jurrie van der Woude, and he was this delightful Dutch guy. And after it had been up on the wall of von Kármán for three or maybe four years at that point, he told me the story that people would admire the whole thing, and then they’d walk up and they would have to touch the Earth. You know, that connection of, “That’s us.” And so, he had to frequently replace that picture, because it was continually getting worn. (laughs)

[36:15] Narrator:It’s amazing that just a simple tap, from enough people, can be so destructive over time, like drops of water that eventually wear down a stone. Since that photo of our pale blue dot was snapped thirty years ago, from the Voyagers’ perspective, Earth has disappeared into the darkness.

Candy Hansen:I’m going to guess that Voyager could still see the big planets, Jupiter and Saturn. It can probably still see Uranus and Neptune. I’m very, very doubtful that it has the sensitivity to see the Earth. Because the Earth, even back then, was smaller than a pixel, and now it’s much smaller.

[37:02] And the Voyagers are out in interstellar space now. That was so exciting when the first one left, and now they’re both out there, and it took a lot longer to get there than anyone would’ve predicted. But that teaches us, right?

Narrator:All the planets and the Sun travel together through the galaxy in a sort of bubble, which scientists call the heliosphere, created by the particles and magnetic field of the Sun’s solar wind. There were lots of ideas for how big the heliosphere could be, but no one really knew how far it extended.

Then Voyager 1 crossed over in 2012, at a distance of about 18 billion kilometers from the Sun, or more than 11 billion miles. Voyager 2, following its own path past Neptune, left the heliosphere in 2018, when it also was about 18 billion kilometers from the Sun.

[37:59] Candy Hansen:It was surprising that it took that long, but I’m so glad that they both are operating long enough to be able to tell us where’s the edge of our bubble that the Sun provides for us, magnetically speaking. And just the thought that they’re on this no-return journey, and they’re going to probably outlive the Earth. Because someday, our star is going to turn into a red giant, and that’ll be that, billions of years from now.

And they’re just going to be out there, scooting along with our Golden Record, and it’s a little piece of not only ourselves, but our time, of what was happening right here, right now.

(Voyager Golden Record music:31/31 String Quartet No. 13 In B Flat, Opus 130, Cavatina, Beethoven)

(Voyager Golden Record greetings)

Armenian: “To all those who exist in the universe, greetings.”

Mandarin Chinese: “Hope everyone’s well. We are thinking about you all. Please come here to visit when you have time.”

Nepali: “Wishing you a peaceful future from the Earthlings.”

Narrator:We’re still talking to the Voyagers, but not for long. Mission scientists estimate in the next few years the spacecraft will run out of power and no longer be able to speak to us.

When we finally say goodbye, the Voyagers will have a long, silent journey ahead of them. It will take many thousands of years for them to fully leave our solar system, where the boundary is marked by a region of comets known as the Oort Cloud. Once they pass through that, given the vast distances between stars, the Voyagers likely will only ever encounter interstellar dust.

(Voyager Golden Record music:Dark was the Night, Cold was the Ground, Blind Willie Johnson)

[40:11] Narrator:When our Sun evolves into a red giant star 5 billion years from now, consuming the inner planets of the solar system in its expansion, including Earth, the Voyagers will still be orbiting the center of the galaxy. From the Voyagers’ view, the end of their birthplace will be signaled by a distant background star shining just a little bit brighter, a little redder than before.

The Voyager spacecraft and their Golden Records are our messages in a bottle, set adrift on the cosmic sea. After Earth is long gone, the Voyagers will be our legacy, still speaking our messages of welcome, and singing our songs.

(music continues)

Narrator: If you like this podcast, please subscribe, rate us on your podcast platform, and share us on social media. We’re “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory.

[run time = 41:31]