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Sun Series: Soaring Toward the Sun

Season 7Episode 7Apr 23, 2024

For the first time, a NASA spacecraft is flying through the Sun's atmosphere. Nour Raouafi, project scientist for Parker Solar Probe, explains why the Sun's corona is the source of one of the biggest mysteries in all of space science. So, what does it take to build a probe that can touch the Sun—including surviving temperatures of 2,500 degrees Fahrenheit and barreling through sudden eruptions of solar plasma—and live to tell the tale? We'll also go inside the fleet of NASA spacecraft studying the Sun from many angles, including the rescue mission to save a wildly spinning observatory before it became lost in space forever.

The cover art display for the NASA's Curious Universe podcast.

Sun Series: Soaring Toward the Sun | About the Episode

For the first time, a NASA spacecraft is flying through the Sun’s atmosphere. Nour Raouafi, project scientist for Parker Solar Probe, explains why the Sun’s corona is the source of one of the biggest mysteries in all of space science. So, what does it take to build a probe that can touch the Sun—including surviving temperatures of 2,500 degrees Fahrenheit and barreling through sudden eruptions of solar plasma—and live to tell the tale? We’ll also go inside the fleet of NASA spacecraft studying the Sun from many angles, including the rescue mission to save a wildly spinning observatory before it became lost in space forever. 

Introducing NASA’s Curious Universe         

Get curious with NASA. As an official NASA podcast, Curious Universe brings you mind-blowing science and space adventures you won’t find anywhere else. Explore the cosmos alongside astronauts, scientists, engineers, and other top NASA experts who are achieving remarkable feats in science, space exploration, and aeronautics. Learn something new about the wild and wonderful universe we share. All you need to get started is a little curiosity. 

NASA’s Curious Universe is an official NASA podcast hosted by Padi Boyd and Jacob Pinter 

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Find the full NASA’s Curious Universe catalog at 

[THEME MUSIC: Curiosity by SYSTEM Sounds] 

HOST PADI BOYD: This is NASA’s Curious Universe. Our universe is a wild and wonderful place. I’m your host Padi Boyd.  

COHOST JACOB Pinter: And I’m Jacob Pinter. In this podcast, NASA is your tour guide.  


PADI: We’re shining a light on the Sun with a miniseries all about our neighborhood star. This is episode number five.  


JACOB: Today’s story starts with an astrophysicist named Nour Raouafi.  


NOUR RAOUAFI: First of all, when you tell people “I do space physics and astrophysics,” they say, Yeah, you guys are the smartest people on Earth.   


PADI: Nour is the project scientist for NASA’s Parker Solar Probe. He’s based at the Johns Hopkins Applied Physics Laboratory.  


NOUR: Well, you know what, probably we are not. Everybody is smart in their own way. But probably what we have is passion and curiosity that we want to know things out there. 


[Song: Robot Reborn by Danny Cullen, Nick Herbertsen, and Tord Jungsten] 


JACOB: Nour’s passion for space started when he was a kid. He was born in Tunisia in the countryside, and he remembers summer nights when he would lay on his back and look up into clear, starry skies. 


NOUR: I asked my father one day why the sun is so hot. And he told me, Well, it’s a ball of fire. But I asked another question, and I asked it multiple times, but nobody could answer it to me. And that question was, How come this fire never goes out? 


JACOB: And, you know, now that you’re a real life astrophysicist, do you know the answer? 


NOUR: Well, I know more about the Sun, but if you ask me honestly, what keeps me interested in it is the things we don’t know. And there is so much about it. 


JACOB: The good news is, we do know a lot about the Sun. After all, we’ve studied it more than any other star in the universe. But there are still huge mysteries to solve.  


PADI: NASA investigates those mysteries in many ways, including using a fleet of spacecraft, which give us all kinds of different views of the Sun. Now we’re getting our closest look yet with Parker Solar Probe—a mission that flies through the Sun’s atmosphere for the first time ever. The probe has already touched the Sun. Later in 2024, it makes its closest approach yet, and Nour and other scientists will be piecing together information to try to solve some of our biggest, burning questions.  


JACOB: To understand those science questions, let’s start with what we do know. For one, the Sun isn’t literally made of fire. It’s a huge ball of hydrogen and helium. 


NOUR: The sun is not really a solid body. It’s a ball of ionized gas, which is, we call it a plasma. So there is no solid surface to land on. But its atmosphere is pretty extended.  


JACOB: The center of the Sun is unimaginably hot: 27 million degrees Fahrenheit. This is where the Sun generates light and heat through nuclear fusion. As you move away from the core, things get less intense. By the time you make it to the layer we see with our eyes, which is called the photosphere, the temperature is down to 10,000 degrees Fahrenheit. Now that’s still hot enough to boil diamonds, but at least it’s not in the millions.  


[Song: Unstable Stem Cells by Andy Hopkins, Ella Ryan, and Jacob Nicholas Stonewall Jackson] 


As you keep going and make it to the Sun’s outer layer, which is called the corona, things get weird.  


NOUR: The temperature of the gas will skyrocket to more than a million degrees Celsius. That is over 2 million degrees Fahrenheit. And that is so puzzling because from everyday experience, if you step away from a fire, from a heat source, it gets cooler. That’s not how the solar corona works. 


PADI: This is one of the biggest mysteries not just about the Sun but of all our questions about space: why is the Sun’s corona so hot? Parker Solar Probe goes right to the source. In 2021, it became the first spacecraft ever to fly through the corona, and it’s still getting even closer to the Sun’s surface. The second big question for Parker Solar Probe also starts in the corona, but it doesn’t end there. The corona is so hot that it essentially boils off a stream of charged particles. Scientists call this “solar wind”.  


[sound from Parker Solar Probe’s “Sounds of the Solar Wind”] 


PADI: Although we can measure solar wind and Parker Solar Probe can even hear it by translating magnetic field data into sound, we don’t totally understand where it comes from.    


NOUR: It starts at low speeds close to the sun. But over a short distance, the particles like electrons, protons, and heavy ions start flowing at speeds of about 2 million miles per hour, meaning they are getting so much energy from somewhere. But we don’t know what is that energy source, and that is so extremely complex and puzzling for us. 


PADI: Job number three for Parker Solar Probe is gathering information about solar flares and coronal mass ejections—outbursts of energy and plasma from the Sun. We’ve gone into detail about those in other episodes of this series. Suffice it to say, they can have serious effects here on Earth. A close-up look from Parker Solar Probe can help us understand them better.  


NOUR: But let me say this: Parker Solar Probe is way, way more than these three phenomena. Parker Solar Probe is venturing into a region of space that we never visited before, and any measurements we make is a potential discovery. 


JACOB: Touching the Sun has been on NASA’s wish list from the very beginning. As far back as the 1950s, scientists have brainstormed a mission like this. But it took decades of refining the plan and solving engineering challenges to get it off the ground.  


[Song: Clean Lines by Ella Ryan and Thom Powell] 


On one level, flying toward the Sun seems pretty straightforward. Our star has enough gravity to keep entire planets in orbit. Surely a spacecraft would get sucked right in.  


NOUR: Believe it or not, it’s extremely hard to get any object close to the Sun, and the reason is pretty simple: because Earth is orbiting the Sun at very high speed, and if you launch a spacecraft from Earth, it will inherit that speed. 


JACOB: Instead of shooting the probe directly toward the Sun, it takes a complicated series of maneuvers using other planets’ gravity to regulate speed.  


PADI: Decades ago, early versions of this mission actually proposed shooting the probe away from the Sun. By circling Jupiter and using its gravity like a slingshot, the probe would fly past the Sun once, screaming by at tremendous speed. 


JACOB: Eventually we found a different way. Instead of Jupiter, the probe relies on Venus’ gravity. But Venus isn’t a slingshot. It’s a way to tap the brakes.  


NOUR: And every time we fly by Venus, we slow the spacecraft a tiny bit. And when you slow it, it will dive closer to the Sun. By doing it multiple times, we gradually decrease the closest approach to the Sun. 


JACOB: In all, Parker Solar Probe will orbit the Sun two dozen times. On December 24, 2024, it makes its closest approach yet: about 4 million miles from the Sun. If that still sounds far, think of it this way: If you built a scale model of the solar system with the Sun and Earth 10 feet apart, Parker Solar Probe would fly less than 5 inches from the Sun.  


PADI: During that close approach, it will also set a new spacecraft speed record: 430,000 miles an hour—fast enough to get from New York to Tokyo in one minute. Besides speed… the engineering team faced plenty of other challenges.  


[Song: Launch Codes by Andy Hopkins, Jacob Nicholas Stonewall Jackson, and Jez Hurst] 


PADI: Here’s one key problem they had to crack: 


NOUR: If you think of the hottest summertime here on Earth, Parker Solar Probe will be exposed that—almost 500 times that heat. It’s extremely hot. So you have to come up with material that is so efficient in dissipating heat and basically act like an umbrella in front of the spacecraft. 


PADI: When Parker Solar Probe is closest to the Sun, its outer layer will be 2,500 degrees Fahrenheit. Engineers came up with a material that could not only survive, it could protect the delicate scientific instruments onboard.  


NOUR: It’s really a piece of carbon foam. That’s what it is. We cannot say how it was fabricated, because that’s the secret. 


PADI: That carbon foam always faces the Sun, and the probe’s instruments sit a few feet behind it. While the heat shield endures temperatures in the thousands of degrees, the instruments will stay at a cozy 85 degrees Fahrenheit—just above room temperature.   


JACOB: With all of that solar energy, maybe it’s not a surprise that the spacecraft gets power from solar panels. But it took some problem-solving to make those survive too.  


NOUR: We know from the get-go that these solar panels will get extremely hot. So we need to cool them down. And to cool them down, for the first time we use liquid. And can you guess what that liquid is? 


JACOB: Um, something cold. Liquid nitrogen? 


NOUR: It is just water.  




NOUR: It’s a gallon of water. That’s all we need it for, which is amazing. It’s a first, by the way, in space. 


JACOB: Solving these technical problems made it possible for Parker Solar Probe to reach a part of space where humans have never explored. Like any mission of discovery, this probe is looking for answers. But it could also show us that we need to ask different questions.  


NOUR: My biggest hope is that we discover new things that we didn’t know before, because that’s what we are looking for. Scientists in a way are weird creatures. People usually look for the easy life. Scientists, they are always looking for problems. And we love them. 


PADI: Nour and the whole team behind this probe are standing on the shoulders of many other scientists who were also obsessed with problems. 


[Song: Obsessions by Carl David Harms] 


PADI: Back in the 1950s—not long before the very first iteration of the solar probe was taking shape—a young physicist was trying to solve his own mysteries. His name was Eugene Parker.  


EUGENE PARKER: I got hold of these old Harvard books on astronomy, which at the time weren’t so old. And I read every one, every volume in the series, something like seven or eight volumes, and I found it very interesting.  


PADI: This is Parker speaking in a TV interview from 1993.  


PARKER: It’s a lot of new physics, a lot of things that happen out there that don’t happen in the laboratory, and it was just fun. Problems that you could actually solve. 


PADI: In the late ‘50s, Parker tried to answer questions about the Sun’s corona. Physicists at the time had already established that the corona was much hotter than they expected. They were debating how far the corona extended. At this point Parker was 31, and he had only been a professor for a few years. But as he made his way through a series of physics equations, he realized he had discovered something.  


NOUR: He came up with a theory saying that the boiling gas, the multi-million degree gas in the solar corona cannot be static. It has to create stream that flows away from the sun, and he called it the solar wind. And he was ridiculed for that idea. 


JACOB: Years later, Parker recalled just how badly other scientists responded. One wrote, “I would suggest that Parker go to the library and read up on the subject… because this is utter nonsense.” Now Parker’s new idea was based on working through equations—not direct observation. So how could he prove this theory?   


MARINER 2 VIDEO: August 26. The Mariner 2 countdown begins. Events move on a strict timetable. Five, four, three, two, one [sound of rocket lifting off]. 


JACOB: At the dawn of the Space Age, NASA was taking its first steps to explore the rest of the solar system. In 1962, a spacecraft called Mariner 2 blasted out of Earth’s orbit headed for Venus.  


MARINER 2 VIDEO: Mariner 2 has successfully traversed 180 million miles of space. February 26, 1963; the preliminary results. At the encounter altitude, Venus has neither the …  [fades out] 


PADI: Mariner 2 flew by Venus and made a series of scans—the first time humans had successfully sent a probe to another planet ever. For astronomers, it was a treasure trove.  


MARINER 2 VIDEO: Years will be required to digest and finally interpret the 65 million bits of data that Mariner radioed back to Earth. 


PADI: And for Eugene Parker, it was a chance to turn the tables.  


[Song: Dream World by Colin Nicholas Baldry and Tom Kane] 


PADI: As it was sailing through space, Mariner 2 detected particles whizzing by at hundreds of miles per second.  


JACOB: It was the solar wind, just as Parker had proposed. This discovery cemented solar wind as a scientific fact, and it was a milestone in the long, legendary career of Eugene Parker.  


NOUR: I knew him for over 20 years. He’s an amazing human being. But Gene Parker’s contribution go well, well beyond just theorizing the existence of the solar wind. He has interest in the galaxy, he has interest in magnetosphere, he has interest in planets. You see him through his career jumping from one research topic to the next to the next.  


JACOB: That thing about Parker proposing solar wind, being ridiculed, being vindicated a few years later—it just seems so interesting. Did you ever get a chance to talk to him about what that was like personally? Or do you know how he felt about that period in his life or anything like that? 


NOUR: This is the nice thing about him. He did not really make a big deal out of it. People disagree with me, we are fine, move on to the next thing. And that was it. 


[sound of applause]  




PARKER: I wrote my speech down here … [fades out] 


JACOB: For most of its development, Parker Solar Probe had a different name. It was originally called Solar Probe Plus. But in 2017, NASA announced the mission was being renamed in honor of Eugene Parker.  


[Song: Detailed Analysis by Carl David Harms] 


PADI: This was a historic announcement. NASA had never named a mission after a researcher during their lifetime.  A few days before his 90th birthday, Parker took the stage at the University of Chicago. 


PARKER: I’m certainly greatly honored to be associated with such a heroic scientific space mission. By “heroic” of course I’m referring to the temperature, the thermal radiation from the Sun, and the extreme measures developed to survive that radiation and collect scientific data should be fully appreciated. As a theoretician, I greatly admire the scientists and engineers whose patient efforts together converted the solar probe concept into a functioning reality ready to do battle with the solar elements as it divulges the secrets of the expanding corona. So hooray for solar probe. Thank you.  


UNIDENTIFIED VOICE: Status check. Go Delta. Go PSP. 


PADI: In 2018, Eugene Parker logged another first. For the first time in NASA history, the person who gave their name to a mission watched it lift off.    


CROWD IN UNISON: Seven, six, five. 


[Sound of cheering from the launch viewing gallery]  


PARKER: There we go  


LAUNCH GALLERY VOICES: Wow. Go baby go! [Cheering] Yay! 


PARKER (from launch broadcast): All I can say is, Wow, here we go. We’re in for some learning over the next several years.  


[Song: Reverse Motion by Lincoln Jaeger] 


JACOB: Once the probe became operational, NASA showed Eugene Parker some of its very first science results. In 2022, Parker died at the age of 94. His contributions to science will last far into the future. And so will the legacy of the probe bearing his name.  


NOUR: He’s one of one of a kind. His contributions are so, so high up there. And more than that, it just makes sense that he’s the only person after whom it is adequate to name this extremely important mission. 


PADI: Just as Parker Solar Probe builds on the work of Eugene Parker and other pioneering scientists, it also relies on what NASA has learned from previous solar missions. Parker Solar Probe is going closer to the Sun than ever. But before it—and alongside it—came a long line of spacecraft showing us the Sun in ways our eyes never could.   


ALEX YOUNG: I think we take it for granted. I mean, we get really beautiful sunrises and sunsets sometimes. And when you look at it from space, when you put telescopes above the atmosphere, there’s all kinds of wavelengths of light that we don’t see with our eyes, that we don’t get here on the ground. 


[Song: Event Horizon by Brandon Seliga] 


PADI: Alex Young is a solar astrophysicist. He’s been studying the Sun at NASA for more than 20 years. NASA’s observatories give us crucial clues about activity on the surface of the Sun, the processes going on inside the Sun, and even its influence to the far reaches of the solar system.  


JACOB: Now, you already know that the Sun produces a lot of light. But our eyes only give us part of the story. The Sun produces all kinds of electromagnetic radiation, from radio waves, to the ultraviolet light that gives you sunburns, to X-rays and gamma rays. In his first job out of grad school, Alex worked on a spacecraft that can see some of those wavelengths. It’s called, Solar and Heliospheric Observatory or “SOHO”. 


ALEX: Once I started seeing the Sun from extreme ultraviolet actually was with the SOHO spacecraft for the first time, it just blew my mind. 


NARRATOR FROM SOHO VIDEO: In orbit more than 1,800,000 kilometers from Earth, SOHO’s position means its 12 instruments can observe the Sun without the interruption of the Moon and the Earth passing in front of them.  


JACOB: SOHO launched in 1995 as a joint mission between NASA and the European Space Agency. It’s still operating today, even though its original mission was scheduled to last just three years. SOHO’s instruments show us aspects of the Sun that no other telescope can. 


ALEX: You can find out what’s happening inside the Sun. We see rivers of superheated gas called plasma flowing inside the Sun. We can see down into where sunspots are forming before we can see them on the visible surface. SOHO was not the first mission to do it, but SOHO provided such amazing data over such a long period of time that it’s given us a completely new perspective 


PADI: But SOHO almost didn’t make it. A few years before Alex joined the team, SOHO was on the verge of being lost in space forever. 


ALEX: We have a euphemism for that called “the vacation”. SOHO took vacation for six months. 


[Song: Mitosis by Carl David Harms] 


HAROLD BENFIELD: Basically, we lost contact. In essence, everything was powered off.  


PADI: This is Harold Benfield. He was SOHO’s missions operations leader at NASA. 


JACOB: The trouble started in 1998, less than three years after the mission launched. The spacecraft was in the middle of a routine maneuver, and then it went dark.  


BENFIELD: We weren’t sure exactly what happened. We were able to piece together a story based on the last thing we saw. 


PADI: SOHO started spinning out of control. The team didn’t know if they could rein it in. Normally SOHO’s power came from solar panels that were supposed to face the Sun all the time. The spin swung them out of line. Not facing the Sun meant no power for the spacecraft. That would make it impossible to communicate, and SOHO could be a goner.   


JACOB: But you know that saying, “a broken clock is right twice a day”? Well, even a spinning spacecraft faces the right direction every once in a while. The team kept sending messages in the hopes that SOHO would hear.   


BENFIELD: We were sending commands in the blind. Obviously, we didn’t know when those periods were. So we send the sequence repeatedly. We’re able to at one point get the transmitter turned on and get a brief burst of telemetry.  


JACOB: Re-establishing contact was great news. It gave the team hope that they could use SOHO’s thrusters to get it back in position. But there was bad news too. In the cold void of space, SOHO’s fuel would freeze without heaters keeping it warm. No solar power meant no heaters. SOHO’s fuel was frozen solid.  


BENFIELD: So you’re thinking about a 200 pound block of ice that you’ve got to thaw with a 40 watt light bulb. So you know, it’s not something that happens right away. It takes some time. 


PADI: Over the course of a couple of weeks, the team gingerly used SOHO’s batteries to bring the fuel back to a usable state.  


BENFIELD: Eventually we were able to do that. And then we were able to fire the thrusters and stop the spin. 


JACOB: Analysis showed that while SOHO was incommunicado, its instruments had been exposed to wild temperature swings from more than 200 degrees Fahrenheit to almost minus 200 degrees Fahrenheit. It was dicey, but SOHO was back. 


ALEX: One of the particular instruments did not survive, and another instrument was partially damaged. So it did have a toll on the spacecraft. But all in all, it came out for the most part relatively unscathed. 


PADI: SOHO’s “vacation” happened more than 25 years ago. During its long life, SOHO has observed an entire 11-year solar cycle and the beginning of another one. It’s also taken on an unexpected side job discovering comets, which you can hear more about elsewhere in our Sun series. Alex says SOHO can teach us a valuable lesson about exploring space.  


ALEX: Absolutely part of the way we learn is by mistakes. If you don’t make mistakes, you don’t—I mean, we don’t really learn unless we make mistakes. 


JACOB: SOHO’s perseverance has allowed it to team up with other spacecraft in NASA’s fleet. Like STEREO, which used twin spacecraft to give us a unique view of the Sun’s activity; Solar Dynamics Observatory, which investigates the Sun’s magnetic changes; and coming soon, HERMES, which will orbit the moon and measure solar radiation as Artemis astronauts head back to the lunar surface.  


ALEX: I still kind of think of the time of SOHO as sort of the golden age of solar physics, because it was such a comprehensive look at the sun, you know, from inside outwards, and then all the things that are coming off the sun. It’s an amazing feat of engineering that it has lasted so long and produced such amazing imagery, still to this day. 


PADI: NASA’s fleet works together, giving us different views of the Sun that we can piece together like a mosaic. And by touching the Sun, Parker Solar Probe gives us close-ups of things we normally see from a distance, like flares and coronal mass ejections.   


[Song: Spyware by Jeremy Holland Smith] 


NOUR: We designed Parker Solar Probe to fly through the through these big coronal mass ejections because that’s the science we were—part of the science we want to do. But still, until you experience it, you don’t really know how the spacecraft will behave. 


JACOB: Scientists call these coronal mass ejections “CMEs” for short. We’ve observed them from a distance, like with SOHO. But flying through one at point blank distance from the Sun is a totally different proposition. 


NOUR: We did a lot of simulations before launch, and we imagined the strongest CMEs ever and see how much how much torque those structure will transfer to the spacecraft. 


JACOB: In September 2022, ready or not, Parker Solar Probe put those simulations to the test.  


PADI: The Sun released a huge CME. We don’t know exactly how big but probably on par with the biggest one ever recorded to hit Earth. Fortunately, the Sun released this outburst to its far side, so we were all safe. But Parker Solar Probe was directly in its path.  


[sound of Parker Solar Probe being hit by a CME] 


JACOB: What you’re hearing is the spacecraft’s collision with that CME. This is magnetic field data converted to audio. At the time, Parker Solar Probe was less than six million miles from the Sun or about one-sixth of the average distance to Mercury. And since it was on the far side of the Sun, it couldn’t communicate with Earth in real-time. It was all on its own.  


NOUR: We think, OK, we have a clear idea about the overall structure of the of the CMEs. But when Parker Solar Probe gave us the first images, it was so complex, it’s like we never seen CMEs before. 


PADI: Data from the spacecraft show that the CME vacuumed up dust floating in space. Scientists had theorized that this was possible, but nobody had seen it before. This deeper understanding of solar activity could improve our space weather forecasts, and that could help keep us safe if Earth does end up in the crosshairs. The data from Parker Solar Probe also showed that its autonomy system worked perfectly. After the impact, it corrected course right away.  


NOUR: This is probably the highest risk mission NASA ever built. But still, it is working so, so beautifully and knock on wood, it will hopefully continue that way. 


JACOB: With Parker Solar Probe running smoothly, Nour says it sets a powerful example for the future. Not every risky mission goes off without a hitch.  


NOUR: Having a mission that is extremely high risk mission with the level of success that Parker Solar Probe has achieved is driving the community to boldness. If you go back, let’s say a decade ago, there are certain ideas and certain missions, we thought yeah, just forget about them. They are not probably not feasible in our time. But now the community is going after these missions, and that’s thanks in particular to Parker Solar Probe. 


JACOB: And with Parker Solar Probe, the best is yet to come.  


[Song: Intimate Nature by Tom Kane] 


In November of this year, the probe will make its final pass of Venus. And on December 24, it makes its closest approach to the Sun and then returns twice next year. 


NOUR: Now that we are going to embrace a star for the first time ever, it’s going to drive the new generations, the young kids to say, You know what, I want to get even closer to a star. I want to go elsewhere in the in the universe. 


PADI: The science data will take time to unravel. Nour is definitely excited to see how that turns out. Scientists will have a lot of work to do and probably some friendly debates about what exactly the data show.   


NOUR: But for me, I want to stress one thing: the achievement that we are going to do in on the eve of Christmas of this year is so humongous. Let me go back to Gene Parker, when he was ridiculed about his theory and all that, and I want to tell every child out there, if you get ridiculed about something, the way the best way to think of it is that that thought or idea is so original, that nobody can get it, except you. 


JACOB: Before we go, we have another installment of our new segment, “What are you still curious about?”  


[Song: Sound Design Digital Uplifting Texture by David Thomas Connelly] 


We ask that question to every single person we interview for this show, and we want to know what you’re curious about too. So it’s time to take a question from a curious listener and track down the answer. Today’s question comes from Charles Bergquist. He’s a senior producer with the show Science Friday. Charles, how’s it going?  




JACOB: You’re a science journalist, so I imagine you’re curious about all kinds of things. But when it comes to space, what are you still curious about?  


CHARLES: Yeah, so recently on Science Friday guest Umair Irfan of Vox was talking with our host Ira Flatow about aa White House request for NASA to create a lunar time zone. And it really got me thinking about, here on Earth we’ve got our hours and our days that are based on how our planet rotates, right? But what happens when humans need to tell time somewhere that doesn’t have that same set of physical references? Like, if you’re on the space station you get a sunrise, what, every 90 minutes or so. So I started thinking about what their clocks are set to and if there are other space time zones. 


[Song: Binary Fission by Tom Kane] 


JACOB: Yeah, so let’s start with the astronauts who are in space now, the International Space Station. Those astronauts use Greenwich Mean Time. It’s the time zone where the prime meridian is in the U.K., and it’s also the basis for a time zone called Coordinated Universal Time, which is kind of like the measuring stick for timekeeping around the world. So the International Space Station is really measuring time based on Earth time zones. For now there is for now no official Moon time. But like you mentioned, NASA proposes creating a new system called Coordinated Lunar Time. And the reason for this is that if you know your theory of relativity, you know that time can tick at different rates in two different places in the universe, depending on location and velocity. This is one of those things that you see in sci-fi movies, like when one character goes off on a space adventure and they age at a different rate from somebody who stays on Earth.  


Well, time on the Moon ticks by at a rate slightly different from Earth, and as we send astronauts back to the Moon—and as we establish a long-term presence there—this will become really important. When you’re dealing with space travel, you need accuracy down to a fraction of a second. So this Coordinated Lunar Time Zone will be traceable to Coordinated Universal Time so we can convert back and forth between Moon time and Earth time, and it will make sure that our clocks are super accurate. 


CHARLES: So if NASA does establish this Coordinated Lunar Time that you’re telling me about, would they need to sort of subdivide the Moon even further into lunar time zones set on that clock?  


JACOB: We don’t expect to have time zones on the Moon, so the new Coordinated Lunar Time scale—it applies to all of the Moon. The main thing is just those differences caused by relativity. 


CHARLES: So if you’re looking at eventually going even beyond the Moon to Mars, are there similar effects with relativity? Do we need different time zones for every place in the solar system we end up? 


JACOB: So this is something that NASA is still studying and will keep studying as we get ready for crewed missions to Mars. It is possible that Mars will get divided into time zones like Earth, although when you think about that, one thing to keep in mind is that Mars is only about half the size of Earth. Just to put it into perspective, if you picture Earth as the size of a nickel, Mars is about as big as a raspberry.  


[Song: Sporangium by Tom Kane] 


And then when the time comes to keep time on Mars, a couple of other things to keep in mind are that a Martian day is about the same length as an Earth day. It’s 24.6 hours. But a year is much longer: it’s 687 Earth days. And one thing that I find really interesting is that on Earth we have these four seasons and they’re spread evenly throughout the year, so each season is three months. But Mars has an orbit that is egg-shaped, so it gives the seasons different lengths. So if you live in the northern hemisphere of Mars, spring is the longest season. Autumn is the shortest, and then summer and winter are in between. And that might not affect how NASA measures time necessarily, but if I moved to Mars, I think it would definitely affect how I perceive time.  


CHARLES: Definitely. 


JACOB: Charles, thanks so much for sharing your questions with us.  


CHARLES: Thanks for having me, Jacob.  


JACOB: That’s Charles Bergquist. He’s a senior producer on the show Science Friday. 


PADI: Thanks for listening to our Sun series here on Curious Universe. We’ll be back with a bonus episode, featuring dispatches from the total solar eclipse.  


If you have questions about the eclipse or the Sun or anything else you want to ask NASA astronauts, scientists, and engineers, drop us a line. You can email us at And we may answer your question in a future episode. Also, you can find so much more about the Sun at 

[THEME MUSIC: Curiosity by SYSTEM Sounds] 


JACOB: This is NASA’s Curious Universe. This episode was written and produced by me, Jacob Pinter.  


PADI: Our executive producer is Katie Konans. The Curious Universe team includes Christian Elliott, Maddie Olson, and Micheala Sosby. Krystofer Kim is our show artist. Our theme song was composed by Matt Russo and Andrew Santaguida of SYSTEM Sounds.  


JACOB: Huge thanks to Michael Chesnes and the NASA Enterprise Library for research help with the archival tape you heard in this episode. Clips from the 1993 television interview with Eugene Parker are used courtesy of the New Mexico Public Media Collection and the American Archive of Public Broadcasting. Some archival clips about SOHO were produced by the European Space Agency. Special thanks to the Niels Bohr Library and Archives at the American Institute of Physics. And an extra special thanks to NASA’s heliophysics team for their help throughout this series. 


PADI: If you enjoyed this episode of NASA’s Curious Universe, please let us know by leaving us a review and sharing the show with a friend. And, remember, you can “follow” NASA’s Curious Universe in your favorite podcast app to get a notification each time we post a new episode. 


PARKER: Curiosity in some quarters is now considered a dirty word, but I don’t think so. I think as humans we naturally would like to know what’s going on, and that’s the ultimate game.  


NASA AUDIO TAG: Three, two, one. This is an official NASA podcast.