Planetary Radio • Jun 19, 2024

A big year for heliophysics and Parker Solar Probe

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Nour raouafi

Nour Rawafi

Parker Solar Probe Project Scientist and Principal Professional Staff at the Johns Hopkins University Applied Physics Lab

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Sarah Al-Ahmed

Planetary Radio Host and Producer for The Planetary Society

Our Sun is nearing the most active part of its solar cycle. This week, we explore recent solar activity and discoveries from NASA's Parker Solar Probe with Nour Rawafi, the mission's project scientist. But first, we honor the life and legacy of Ed Stone, the former director of NASA's Jet Propulsion Laboratory and the longtime project scientist of the Voyager mission. We close out our show with Bruce Betts, the chief scientist of The Planetary Society, in What's Up.

Tribute to Ed Stone

Ed Stone, the former director of NASA’s Jet Propulsion Laboratory and the longtime project scientist of the Voyager mission, passed away in early June 2024. Here are some of the memories shared with us by Ed’s friends and colleagues.

  • Mat Kaplan, Planetary Society Senior Communications Advisor

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  • Jim Bell, Past President (2008-2020), Board of Directors of The Planetary Society

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  • Eberhard Mobius, Professor Emeritus at the University of New Hampshire Space Science Center and Department of Physics and Astronomy

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  • Alan Cummings, Senior Research Scientist at Caltech

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  • Allan Labrador, Staff Scientist, Caltech Space Radiation Laboratory

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Ed Stone with Voyager
Ed Stone with Voyager Ed Stone, the former director of NASA's Jet Propulsion Laboratory and the longtime project scientist of the Voyager mission, passed away on June 9, 2024. He was the director from 1991 to 2001 and led the iconic Voyager mission for 50 years.Image: NASA / JPL-Caltech
Solar orbiter and Parker Solar Probe
Solar orbiter and Parker Solar Probe ESA’s Solar Orbiter and NASA’s Parker Solar Probe are two complementary missions studying the Sun up-close. The graphic is an artistic impression only, and not to scale.Image: ESA
Parker Solar Probe team receives the NASA Group Achievement Award
Parker Solar Probe team receives the NASA Group Achievement Award Nour Rawafi, the project scientist for NASA's Parker Solar Probe, accepted the NASA Group Achievement Award on behalf of the team from Peg Luce, the acting director of NASA's Heliophysics Group meeting at Johns Hopkins Applied Physics Lab, on Nov. 6, 2023.Image: NASA / Johns Hopkins APL / Ed Whitman
The surface of Venus from the Parker Solar Probe
The surface of Venus from the Parker Solar Probe On Feb. 9th, 2022, NASA released this image from the Parker Solar Probe, which it took during a flyby of Venus. It is the first confirmed visible light image of the surface of Venus taken from space.Image: NASA/APL/NRL


Sarah Al-Ahmed: Solar maximum is just around the corner and the Sun's been putting on quite a show. We're diving into the intense world of solar science with Parker Solar Probe this week on Planetary Radio. I'm Sarah Al-Ahmed of The Planetary Society, with more of the human adventure across our Solar System and beyond. We are right in the middle of the Heliophysics Big Year and the Sun is not disappointing us. Did you catch the amazing aurorae last month? The Sun's activity was so intense that the northern and southern lights were spotted dancing in unexpected places. It's the perfect time to discuss recent solar events and discoveries with Nour Rawafi, project scientist for NASA's Parker Solar Probe mission. But first, we'll honor the life and legacy of Ed Stone, the former director of NASA's Jet Propulsion Laboratory and the longtime project scientist for the Voyager missions who recently passed away. And of course, we'll close out our show with Bruce Betts, our chief scientist in What's Up? If you love Planetary Radio and want to stay informed about the latest space discoveries, make sure you hit that subscribe button on your favorite podcasting platform. By subscribing, you'll never miss an episode filled with new and awe-inspiring ways to know the cosmos and our place within it. We now take a moment to honor the extraordinary life and career of Dr. Ed Stone, a trailblazer in space exploration who passed away earlier this month at the age of 88. Ed had a passion for discovery that propelled him to the forefront of space science, serving as the director of NASA's Jet Propulsion Laboratory from 1991 to 2001 and leading the iconic Voyager mission for an astounding 50 years. His impact extended far beyond the science though. He was a mentor and a gifted communicator who inspired countless scientists and engineers. We've received some beautiful and heartfelt messages from his colleagues and friends that we'd like to share in his memory. Here are some of their reflections on Ed Stone's contributions to the space community and their lives.

Mat Kaplan: This is Mat Kaplan, senior communications advisor for The Planetary Society and former host of Planetary Radio. I envy the scientists and engineers who worked for and with Ed Stone, some of them for many decades. My five encounters with him were relatively brief, but they allowed us to talk about the things he seemed to care most deeply about. Ed was always ready to share his profound dedication to exploration of our Solar System and beyond. Like every great scientist I've met, he also wanted everyone to experience the passion he had for this quest. And like all great leaders, he wanted to help all around him be their best. It has been my honor to interview five JPL directors. Each brought or brings unique qualities to the job of running the world's foremost center for robotic exploration. None surpassed Ed's ability to do this with soft-spoken determination and purpose. His voyage will continue for as long as we pursue it, which I trust will be for as long as his spacecraft will wander among the stars.

Allan Labrador: My name is Allan Labrador and I have worked in Ed Stone's group at Caltech Space Radiation Laboratory for over 20 years. As with many others, I'll always remember Ed as an insightful scientist, a strong leader and a great mentor. But the memory that is most personal to me is when I defended my PhD thesis. Ed was chair of my committee. I don't remember my thesis defense much. After I finished, I was sent out of the meeting room to await the committee's decision. I don't remember how long I waited, but I remember the sound of the door opening behind me. I turned to see Ed walking toward me smiling, with his hand outstretched. And he said, "Congratulations, Dr. Labrador." It was the first and remains the most meaningful time anyone had ever called me Dr. Labrador, and I will cherish that memory.

Alan Cummings: My name is Alan Cummings and I am a senior research scientist at Caltech. I work in the space radiation lab that Robbie Vogt and Ed Stone founded way back in the '60s. And I've known Ed Stone for 57 years. Ed was a brilliant scientist, and he was the best multitasker I ever met. One example of that was when he was a JPL director for 10 years in the '90s, he was still working on projects at Caltech in his lab. He worked closely with me on Voyager data in the evenings and weekends. And one time, I was at the chalkboard and Ed was in the office and we were discussing something about our Voyager data. And he got interrupted and said he had to go to Washington DC right now because he needed to meet with the NASA administrator. So, he left. And a few days later he comes back and he comes back to my office. And he motions me up at the chalkboard, I get up there. And we resume our conversation just where we left off, right in mid-sentence. We didn't need to go back over anything for Ed. He was on top of it.

Eberhard Mobius: My name is Eberhard Mobius, professor emeritus at the University of New Hampshire Space Science Center and Department of Physics and Astronomy. I admire so much his gentle but very firm leadership. I remember vividly my first visit to Caltech, when I mentioned to him the idea that perhaps Alfvén's critical velocity might play a role in the observed abundance patterns in the solar corona and cosmic waves. He rushed me to the Caltech library in his well-known stride to find relevant articles. The idea didn't hold up, but I preserved a wonderful memory of my first meeting with Ed Stone. In a colloquium at MPE in the mid 1980s, Ed unveiled an audacious yet conservative vision for the Voyager continuing for another two decades. As we now witness, sheer reality has even surpassed his predictions. Among others, Voyager is a testimony to the depths of his understanding, his vision and the magnitude of his contributions to space science. Dear Ed, thank you so much for your inspiration and support. Travel safely on your last journey.

Jim Bell: Hey, this is Jim Bell, planetary scientist from Arizona State University, member of the board of Planetary Society and past president of the Society. I first encountered Ed at JPL during the Voyager Uranus and Neptune flybys in the 1980s, when I was working as an undergrad for a member of the Voyager imaging team. I have to say, I was immediately impressed by his calm and collegial demeanor during the intense and stressful times around those flybys for the scientists and engineers involved. And I was also impressed by his clear conversational style with the international media because, of course, the spotlight was on Voyager as the space event of those times. More recently, I had the pleasure of actually getting to know Ed in person when he helped provide, over the course of several years, a number of interviews and reviews of material for my book about Voyager called the Interstellar Age. Ed provided an enormous amount of cheerful and selfless guidance that was absolutely critical as I struggled to understand and translate many of the very technical and esoteric concepts of Voyager's interplanetary and interstellar fields and particles, instruments and research. And of course, this was Ed's specialty. Ed Stone was a brilliant and impactful scientist, instrument builder, mission team leader and a talented and effective public communicator. And he was also a great friend of The Planetary Society. He'll be greatly missed as a mentor and a colleague in our community.

Sarah Al-Ahmed: We also received this message from Gary Hunt, a member of The Planetary Society's advisory council. Gary worked for JPL on the Viking missions to Mars and the Voyager Grand Tour of the Outer Planets. Gary wrote, "Ed Stone was a brilliant and inspirational scientist, and an outstanding leader of the everlasting Voyager mission, and a wonderful friend and colleague for more than 50 years. Every one of us involved in the Voyager mission have so much to thank Ed Stone for. Ed Stone will be missed by all of us. However, the Voyager spacecraft continuing on their paths as messengers from Earth to distant worlds will be an everlasting memorial to his lifelong contribution to science and space exploration. He will be missed greatly." You can listen to the extended versions of these recordings on the webpage for this episode of Planetary Radio at And if you want to add some of your memories of Ed Stone to our page, please feel free to email me at [email protected]. The Voyager spacecraft are still venturing into the uncharted depths of interstellar space. But closer to home, our star has been stealing the spotlight. The Sun goes through a solar cycle that takes about 11 years, transitioning from a relatively calm star to a crescendo of solar storms called solar maximum. We're almost at that maximum now, which is why we've been experiencing so many Sunspots and solar flares. And in the last year, we've had an annular and total solar eclipse in North America. To mark all of the solar festivities and research that's happening all around the world, scientists and space enthusiasts have been celebrating a year-long event called the Heliophysics Big Year. And in the midst of all of this, we've recently had a flurry of powerful solar flares that produced the strongest geomagnetic storm to impact Earth since 1989. Today, we're discussing the recent solar events and discoveries with Dr. Nour Rawafi, an astrophysicist at Johns Hopkins Applied Physics Lab, and the project scientist for NASA's Parker Solar Probe mission. This spacecraft, designed and managed by Johns Hopkins Applied Physics Lab in the United States, was launched in 2018. Parker Solar Probe is on a daring journey to unlock the secrets of our Sun's corona or our star's outer atmosphere. And it's soaring closer to our Sun than any spacecraft ever has before. In order to do so, it has to endure some scorching temperatures and the intense radiation to gather data. Nour Rawafi's research explores the mysteries of the corona. He's an expert on solar magnetic fields, coronal mass ejections, shockwaves, and the solar wind. With Parker Solar Probe venturing closer to the Sun than ever before, Nour Rawafi is leading the charge in unraveling some of the biggest questions about our nearest star and how that impacts life on Earth. Hi Nour, welcome back on Planetary Radio.

Nour Rawafi: Hello Sarah. It's really a pleasure to be with you to talk about the Sun, Parker Solar Probe, and many other things.

Sarah Al-Ahmed: I have to mention, I love your name. Because my family almost named me Nourah, which means light in Arabic. So, I feel like that's a really fitting name for a solar scientist.

Nour Rawafi: No, absolutely. And actually, many times I've been introduced and the first thing people say about my name, "Your name means light and you are working with light all the time. So, you are born for that"

Sarah Al-Ahmed: On point. And I know it's been a few months since the Parker Solar Probe team received NASA's Group Achievement Award, but I wanted to send our congratulations. That was awesome.

Nour Rawafi: Thank you so much. I think the team has been doing an amazing job and they deserve all the recognition they are getting. By the way, this is our fifth award in five years. Hopefully, we'll make it to seven. Because our prime mission is seven years, and my goal is to make seven awards for Parker Solar Probe in the first seven years.

Sarah Al-Ahmed: Well, it keeps beating records and then beating its own records. I think at this point it's the closest mission to go to the Sun, the first one to touch the Sun, the fastest human-made spacecraft, and I want to say the first one to fly through a coronal mass ejection that close up. Is that the four records right now?

Nour Rawafi: Yeah. It's the first one to fly through the solar corona, through the coronal mass ejection, closest to the Sun ever. So yes, absolutely.

Sarah Al-Ahmed: Man, that's an intense thing to go through. But thankfully, this spacecraft is designed to do exactly that. And we've gotten so much amazing science out of it. But for people who haven't listened to your appearance on the show before or other Parker Solar Probe episodes, how did you design this spacecraft in such a way that it can take not only flying through the corona but through a coronal mass ejection?

Nour Rawafi: Parker Solar Probe, to start with, is not really new idea at all. People start thinking about a probe to fly close to the Sun back in the late '50s. But it took us over six decades to build a spacecraft that can fly safely close to the Sun. And it took us six decades because simply we did not have the technology to do so. Back in 2001, NASA has commissioned the Applied Physics Lab of Johns Hopkins University to look into material to build the heat shield. Because without the heat shield, we cannot fly close to the Sun. And it took us five or six years to come up with the right material, the right design and everything. And it's then, when NASA decide to go ahead with the mission. So, it's really been a matter of having the technology to mature enough that you can build the spacecraft that is robust to withstand the harsh environment around the star. And when you say a harsh environment, it's probably one of the harshest environment you can ever fly through. But still, Parker Solar Probe, it's been orbiting the Sun for almost six years now, and the spacecraft is pretty healthy. And knock on wood, it'll continue so. And honestly, if you ask any team member before the launch, although we did not speak out loud about it, but we were pretty nervous. We didn't know how this spacecraft would behave close to a star. But from the get-go, Parker Solar Probe was doing so well, way better than we expected. And as a consequence, the mission's expanded so much. Now, we are doing so many things that before the launch, we thought we wouldn't be able to do. It's thanks to all, probably the most marvelous team that put so much effort into this mission to make it one of the most successful missions in NASA's history.

Sarah Al-Ahmed: I remember thinking that when I was first seeing the videos in the lead up to Parker Solar Probe's launch. They did these wonderful explanation videos where they would have a piece of the heat shield, people would put their hand on one side and then blow torch the other. I mean, not like a blow torch is as intense as the Sun. But at that moment it, kind of crystallized in my brain this was actually possible. Which is amazing considering what you guys are pulling off.

Nour Rawafi: Absolutely. The heat shield is one of the components that enabled the whole mission. Without it, we wouldn't do the mission. But wherever you look on this spacecraft, there is edge cutting technology. If you look for example at the solar panels, conventional solar panels cannot work close to the Sun, so we have basically to reinvent new solar cells. And on top of that, you have to cool them down. Because when we are close to the Sun, they get pretty hot. And we use a liquid-based cooling system. And the liquid we use, many people will not even [inaudible 00:16:23] is simply [inaudible 00:16:25] water.

Sarah Al-Ahmed: Really?

Nour Rawafi: Yeah, just simply [inaudible 00:16:28] water. That's what we use to cool down the solar panels. But to me, one of the most amazing aspects of Parker Solar Probe, and by the way this will impact all future missions, is the autonomy system. So, when we are flying close to the Sun, we cannot talk to the spacecraft and probe has to deal with any problem it might run into on its own. We cannot do anything to it. So, the autonomy system we have on board of the spacecraft can run Parker Solar Probe for up to almost two months without any human intervention whatsoever. And to me, that's really amazing. The amazing part of it is, the team members who designed this autonomy system thought every potential problem that the spacecraft might run into and come up with a solution to it. And so far, it's been working flawlessly. It's amazing.

Sarah Al-Ahmed: That's really impressive. Trying to even anticipate all of the edge cases when you're literally flying that close to the Sun is really difficult. And this kind of automation, we've seen really upend things all across the Solar System with different planetary missions. Especially when you're trying to communicate with something that's really far away, that time delay can be really challenging. But if the time delay is intersecting all of this radiation and all these particles coming out of the Sun, I can't even imagine that you could even get a signal through.

Nour Rawafi: It's pretty hard. It's pretty hard. When we are close to the Sun, just forget it. You cannot talk to the spacecraft. It's as simple as that. And that's why probe has to stand on its own facing a huge star. We didn't know how this small spacecraft will face this star that we never flew by before. We didn't know how it's going to behave. One of the scenarios, it might actually encounter major problems, it might actually fail. While it was one of the possibilities, but we tried to do everything possible, do every source of tests on the ground to make it fly and fly safely.

Sarah Al-Ahmed: Well, your team has done a fantastic job. All of those awards are well-deserved. And I wouldn't be surprised if you hit the number seven.

Nour Rawafi: Thank you.

Sarah Al-Ahmed: Earlier this episode, we took a moment to honor Ed Stone from the Voyager missions. And I wanted to take a moment to share The Planetary Society's condolences to you and your team for the loss of mission director Apurva Varia. I know that's a very difficult thing. He contributed so much to solar science and was an inspiration to so many people. I wanted to pass that along.

Nour Rawafi: Thank you so much. Losing a team member is always difficult. It's not really an easy thing. Because you live with the team for years. And it's not really a team anymore, it's family. And when you lose a family member, it's not really easy. But still we keep all the nice memories about him and about Ed Stone. Yeah, it's a bit difficult.

Sarah Al-Ahmed: Yeah. Here's to all the giants whose shoulders we've stood upon. And I'm sure, one of these days, people are going to look back on your contributions and think very much the same thing, because this mission is blowing my mind. Every time I look into more of the data and the results coming out of it, it's just absolutely spectacular. Well, we're in the middle of the Heliophysics Big Year, which is a global celebration of solar science that ran from October 2023, which is when we had an annual solar eclipse, all the way to the end of this year. And there has been a lot to talk about in solar physics. We just passed a solar eclipse, a total solar eclipse on April 8th that went through Mexico, the United States and Canada. Did you get a chance to see it?

Nour Rawafi: Yeah. I was in Carbondale. I saw the eclipse. Seeing an eclipse is always exciting and amazing. Because there is no eclipse that look like another one. The solar corona is always changing. And whenever you see one, it's a new experience all the time. But when you see the excitement of the people out there about this celestial event, that's another component of it. It's not only the moon coming between us and the Sun, it's actually the whole atmosphere that they build up to it and everything. It's amazing. I can tell you a little story. I was at Dallas, flying to give a colloquium about solar eclipse. And I had some material with me to give away. And some of them are the glasses for the eclipse. And members of the TSA crew, actually one lady asked me, "Are these solar eclipse glasses?" And I didn't even tell her yes or no. I told her, "How many do you want?" And I gave her some. Then another one came, then another one came, then another one came. I think at the end I was surrounded by seven or eight of them. And we were talking about the eclipse, talking about the Sun. They even asked me about the largest star in the whole universe. That, to me, showed the degree of how this remarkable phenomenon, the spectacle, total solar eclipse, how much attention it attracts out there. And it's an opportunity for us to talk to everybody out there about what we do, what we know, what we don't know, what we should do in the future. And it's really fun.

Sarah Al-Ahmed: I've mentioned this on the show before, but honestly, when you get a whole bag of solar eclipse glasses to start passing them out to people, you become a hero. Because people, they need those glasses, they get hard to find around the time of the eclipse. What was the spacecraft doing around the time of the eclipse?

Nour Rawafi: Parker Solar Probe, just a few days before the eclipse, flew very close to the Sun. And during the eclipse, it was on its way out, flying away from the Sun. It was still very close to the Sun. But the amazing thing is, we have the other spacecraft, which is an ESA-NASA mission, Solar Orbiter. The two spacecraft came so close to each other, they were almost on top of each other. And also, the other coincidence as well, they were in the plane of the sky as seen from Earth. So when we see the solar corona, Probe and Orbiter were actually flying through the structure we saw during the total solar eclipse, which is so fascinating. So, we see the eclipse from the Earth and Probe and Orbiter are taking measurements from there. And when you combine the two, you get outstanding things that we didn't get before.

Sarah Al-Ahmed: I'm looking forward to seeing what kind of results we get out of that. Because in 2017, we were near a solar minimum. It was still a spectacular total solar eclipse. But we are gearing up for a solar maximum that even now has been impacting us here on Earth with a bunch of solar storms and solar flares. Comparing those two, it's going to be fascinating. What do you think the experience of the solar corona was like during this solar eclipse versus previous eclipses you've seen?

Nour Rawafi: You talked about the 2017 solar eclipse. The Sun was extremely quiet back then. And when you look at the structure of the corona, it was much simpler what we saw in April, simply because the Sun was very quiet. But still, the soul of corona is always complex. And the complexity comes from the complexity of the physics that is ongoing with the solar corona. But when you compare the total solar eclipse of 2017 to the one we witnessed back in April, there is way more structures in the last eclipse in April than in 2017. And that's simply because we are very close to solar maximum and the Sun is so active. And it creates all sorts of eruptions and structures in the corona and you can see all of them. It's just fascinating. The nice thing as well... You were talking earlier about the Helio Big Year. And this really, I would call it the Helio Super Big Year simply because... You mentioned the annular eclipse back in November 2023. And April 8th, we got the total solar eclipse. Exactly a month later, to the day, we got the solar and geospatial super storm where we saw aurorae almost around the globe. And that's really unprecedented. Obviously, the Sun keeps active all the time. But by the end of the year, on Christmas Eve, we will be hitting the closest approach with Parker Solar Probe. And that's something we have been waiting for for over 60 years. All the excitement, it's building up for Parker Solar Probe to give us something marvelous at the end of the year.

Sarah Al-Ahmed: I'm just sad we didn't get to see a coronal mass ejection during the eclipse, but maybe in 2026.

Nour Rawafi: Why not? Yeah. That's actually one of the things I said about the solar eclipse. I gave I don't know how many interviews. And they said, "There is one thing that we have not seen before." Yes, a coronal mass ejection seen by you with the naked eyes. Close to solar maximum, yes, the opportunity is there. We didn't have it. But there will be many solar eclipses in the future. We will see it one day.

Sarah Al-Ahmed: Speaking about aurora and all these solar storms we've been having, you brought up a lot of the solar activity that we had in May. And we had this massive series of storms, some X-Class flares going on that caused some geomagnetic storms. And we were able to see the aurora in much more equatorial latitudes. I believe this was the largest amount of solar stormage we've gotten out to Earth since the late 1980s.

Nour Rawafi: No, this storm is actually the third strongest in the whole space age.

Sarah Al-Ahmed: Yeah. We're lucky it wasn't full Carrington Event. But you never know. And that's part of why studying the Sun is so important in these cases. Because as a technologically advanced civilization, solar storms can truly impact us. I know I've had some friends be worried that they personally, their bodies, might be damaged by these solar storms. And we're totally fine there. But how can it impact our other systems here on Earth?

Nour Rawafi: To your point, I was asked before when this storm was ongoing, and the advice I gave everybody, "Go out there and enjoy the aurora." Nothing will happen to us. We are not going to go extinct. Everything will be fine. If anything, technology will be affected a little bit, but that's it. But I told people, the nice thing about this storm that we knew it's coming, so there are certain steps that have been taken to mitigate some part. And that's actually our goal, is to understand how the Sun behaves, how it works, how it produces all the spectacle. That way, we can mitigate its impact. I think the first assets that can be affected are space equipment like satellites, communication or GPS. But most importantly, to me, it's going to be a big, big deal for us to deal with, by the end of this decade, we're actually going to land women for the first time and men return. And actually, it's not going to be a short visit. The plan is to have a permanent presence there. The only thing is, unlike Earth where we have this magnetic bubble that is protecting us, out there on the moon, there is nothing to protect astronauts. So, we have to keep an eye always on the Sun. What the Sun is doing, what it is throwing to our way. That way, we keep these folks out there, very safe. That's one of the aspects of solar activity. The other aspect is, it can actually affect us even much, much lower, here near the ground. For example, if you take the last storm, certain flights that usually have polar routes, they are more actually to local latitudes to avoid the high doses of radiation that is due to these storms. I'm pretty sure there are other measures that were taken to protect any potential impact to the power grid. And there are other aspects as well that can be impacted by solar activity.

Sarah Al-Ahmed: And trying to anticipate how long it takes for these systems to impact Earth is a complex but really important question. And one of the results coming out of Parker Solar Probe that I found really fascinating recently was the interaction between these coronal mass ejections and interstellar dust that falls into our Solar System. This was such a fascinating one. Because we know that particles from beyond our Solar System can make it in here, but it didn't really occur to me that it could impede or change how fast material from the Sun reaches us. What were some of the results that we saw out of this flight through a coronal mass ejection?

Nour Rawafi: The strongest coronal mass ejection that Parker Solar Probe flew through was on September 5th, 2022. That CME was traveling at more than 2,500 kilometers per second. It was a huge event. And Parker Solar Probe was very close to the Sun. The funny thing, it was actually in the back side of the Sun, so we don't know what probe is doing. So, we have to wait for several days to figure out whether Parker Solar Probe survived and what it did. But when it emerged on the other side, we knew everything is fine, we knew we had plenty of good data to look into. There are many things that are so surprising about this event. First of all, the view we get from them when we are observing them close by, it's way, way different than when you see them from one AU. The internal structure and the complexity within this structure is mesmerizing. But also, the impact on the environment they are flying through is mind-boggling. We knew that whenever you have big events like the one of September 5th, 2022, they will clear the plasma in front of them. But the most surprising to us is, even the heavy dust particles, they were cleared by the CME. And what is left behind them is a near perfect vacuum. Parker Solar Probe, when it was flying through there, when you see the images that we got from probe, it's like it's flying through the darkest night you can imagine. Because it was flying through vacuum. And it took hours for that medium to be repopulated again by gas and dust and everything. And that was kind of surprising to us.

Sarah Al-Ahmed: That's hard to imagine given the videos coming out of it before. Whenever it's flying through the corona, it's just a cascade of particles and little zoomy things. I can't even imagine getting nothing back on that camera.

Nour Rawafi: It's fascinating. The first warning you get is you get this shower of the particles hitting the detector. That, you see it very clearly. And we've seen it before from more AU. When I look at one of those movies and you see... Actually, we call it the snow shower. That's actually, if you are out there in space, that's the type of radiation you are getting, your body will be receiving from the Sun. And that's what we have to protect the astronauts from.

Sarah Al-Ahmed: We'll be right back after this short break.

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Sarah Al-Ahmed: I anticipate a future where we're going to need several Parker Solar Probe like orbiters around the Sun just so we can anticipate space weather to protect our astronauts. Because if we're going to be out on the moon, if we're going to send people to Mars, we're going to need to know about this. Because even this recent solar storm caused aurora, we could see from the rovers on Mars. That's amazing.

Nour Rawafi: Yeah, exactly. Actually, we are thinking about that as we speak. Going forward, we are not going to launch one spacecraft at a time. The community out there is thinking about launching constellations of spacecraft. When it comes to the Sun, for instance, we are thinking of a constellation of spacecraft that will look at the Sun from different viewpoints. That way, you observe the Sun as a ball. It's not anymore like a disk. You see it here from one viewpoint, you only see one side of it. Now, we want to see the whole thing. And there are reasons for that. First of all, whenever you see a movie of the Sun, particularly in [inaudible 00:34:02], you see a lot of things changing. Because the magnetic field is changing all the time. And if you don't follow magnetic fields all the time, you are actually losing information. There is buildup for the energy until the magnetic field explodes, snaps and then produces this. And if you don't follow it, you cannot really predict this event. Now, we need full coverage. We don't want to lose any moment through the evolution of these structures. The other thing also, it's big puzzle for us, is what is happening in the solar anterior itself, where all the magnetic field is generated and come to the surface. And for that one, we need almost a constant view of the solar poles for an extended period of time. And you cannot do it in one spacecraft. You need a whole constellation that will look at the Sun all together. And this is not sufficient. We need actually more than that. Because what we want to do really is look at the Sun and make measurements in the Earth environment in exactly the same time in the magnetosphere and the thermosphere, the ionosphere. Because we want to measure what the Sun is doing and measure its impact in the Earth environment. That way, we have the full picture of what is going on. And talking about the superstorm of May, last month, we're actually organizing a workshop here at the Applied Physics Lab in late October. That will focus only on these four or five days. But for this one, we're going to bring scientists from the solar side, from the magnetosphere, ionosphere. We'll put them all in the same room. And we're going to only talk about this two or three days and what happened there.

Sarah Al-Ahmed: What's very interesting about this is that it doesn't just impact how we think about our Solar System and our Sun's relationship to our planet. But as we're looking out toward other exoplanetary systems, there's so much about these planets that we can't anticipate because we don't understand how they interact with their stars. And it's true, most of the stars in our galaxy aren't stars like our Sun, they're much smaller stars. But even just any understanding of it at all could open up huge doors in exoplanetary understanding.

Nour Rawafi: Absolutely. The Sun in its heliosphere is the best laboratory to try to understand what faraway stellar systems are doing. And to me, the biggest question that we all want to answer is whether we are alone in this universe. And when I say alone, it's not necessarily we want humans like us elsewhere, whether life itself exists elsewhere. But it's really hard to imagine that among all these stars we have out there, there is not a place like us here world life can thrive. I think we have to look for it, we have to keep looking. But to your point, we have a laboratory here. We know that life developed and it's flourishing and everything. And whatever we learn about it will actually help us. As a matter of fact, later this year, we are going to launch the Europa Clipper mission. It is going to study Europa. And Europa is one of the places where we have high hopes that probably there is life. By the end of the decade, we will be launching another mission to Titan that is being built here at APL.

Sarah Al-Ahmed: Dragonfly is one of my favorite missions.

Nour Rawafi: Dragonfly, oh my goodness.

Sarah Al-Ahmed: It's so cool.

Nour Rawafi: It's amazing. And there again, the goal is not really, we want to look at how Titan looks like. But there is reason behind it. We want to figure out whether life is developing there, whether there is chemistry that might lead to life. And we are looking for all signs. And again, our best laboratory is the Sun and its environment. There is another thing also. Really, I have to mention this every time I talk about Sun. Whenever we talk about solar activity and solar storms, we always think about the negative aspect of it. Yeah, it's going to affect technology, it's going to affect humans. But when you think of it, without the Sun, without the solar activity, we wouldn't be here talking together today. Without that, life would not have kicked in on Earth at all. And we owe our existence, our very existence to the Sun.

Sarah Al-Ahmed: We're coming up on Asteroid Day on June 30th. And there was a result about one of the meteor showers that we experience once a year, the Geminid meteor shower, which I believe is in December. And usually, meteor showers are caused by comets. When they get too close to the Sun, they spew a bunch of debris. And when we pass through that debris field, we see meteor showers. But the Geminid meteor shower seems to be caused by an asteroid, the 3200 Phaethon. And we didn't know how that was possible until Parker Solar Probe ended up in this mix doing science on this asteroid. What did we learn about this meteor shower and why were we studying an asteroid with the spacecraft?

Nour Rawafi: That's actually one of the fascinating things. You design space mission to do something, but you end up doing so many other things with it. We did science on Venus with Parker Solar Probe, planetary physics, and we are looking at comets. We are looking at Phaethon as an asteroid. And the fascinating thing about Phaethon, whenever we fly by the Sun, we see this trail and the images, that's actually the orbit of Phaethon. All the debris that is orbiting along that trail. And that's actually the origins of the meteor shower Geminids. And one of the fascinating things is Phaethon is an asteroid, but sometimes it acts like a comet. It releases all this material that leaves behind to form all that trail. We have an undergrad student in Princeton. He has really probably the best eyes in the world. He noticed something, that when you plot the orbit of Phaethon itself, that trail of debris is always a little bit outside of the orbit. And he asked the very smart question, why that is. Why it's not on the orbit and why it's not inside the orbit? And then, he did some numerical simulation and showed there are two processes to release material. If you have gradual process like comets, that material will settle a little bit inside of the orbit when we are close to the Sun. But if it is a catastrophic event, then that material will settle a little bit outside of the orbit. And that's the case of Phaethon. What we think now is that Phaethon, maybe 2000 or 3000 years ago, a catastrophic event happened to it. It might be an explosion. We don't know what it is. It's all speculation now. But it's a catastrophic event that led to the formation of the trail that is the source of the Geminid shower. And this is from a mission that we didn't even decide to look at. I can tell you something else about synergistic science from probe. So, whenever we fly by Venus... We use Venus to get closer and closer to the Sun, so we love Venus a lot. But whenever we fly by Venus, we turn all our instruments. And one of the best flybys for us is when you fly in an eclipse formation. You are actually flying behind the planet, on the night side of the planet. One of the problems we set early on is to look for clouds in the Venus atmosphere. And for us who are not really physicists at all, we saw some dark structure and we were excited, "Yeah, these are the clouds." Only, when we look at other images from years ago from Venus, we saw exactly the same structures. It was kind of disappointing. "Yeah, this is not." But for us, it basically ended up there. I was talking about this observation during the colloquium. And when colleagues here who are specialists of Venus saw them, they were so excited about that. So they got the data, they worked with the data. And guess what? They discovered the shortest wavelength thermal emission from the surface of Venus. So, Parker Solar Probe basically discovered a new window to study the surface of Venus. And from there, using the same observations, we're actually getting some ideas and some results about the raw composition on the surface of Venus. So, Parker Solar Probe in a way is giving hints to future missions that will orbit Venus and study Venus in way, way more detail than Parker Solar Probe. But it's opening windows for them. Look here, look there, look there. And that is really fascinating.

Sarah Al-Ahmed: Well, there's so much about Venus that we don't know. And we've got all these wonderful upcoming Venus missions. We've got JAXA's Akatsuki mission that's been looking at it. There is so much we don't know about that world because its atmosphere is so thick and so deadly. Anytime you try to send something to the service, it fries or melts. But the spacecraft actually has one more Venus flyby coming up. It's the last one. Is that correct?

Nour Rawafi: It's the last one of the probe mission, yes.

Sarah Al-Ahmed: And is it going to send it into a trajectory that's even closer to the Sun? That seems a little wild.

Nour Rawafi: Yeah. The last Venus flyby, which will be on November 6th of this year, will set us for the closest approach ever to the Sun. And this is the nice thing about this Venus flyby. It'll be also the closest to the surface of the planet itself. We'll fly in an eclipse formation, again, with Venus. So, it's an opportunity for us to study the surface of Venus and the atmosphere of Venus. We'll be so deep into the atmosphere of Venus that, honestly, we don't know what we're going to measure there. We'll be in the ionosphere and we'll measure things. We have a full program for that Venus flyby. It's already developed, already in place. And that data will be coming as soon as we fly by Venus. We cannot anticipate to look into it. So, that last Venus flyby will set us for the closest approach ever to the Sun, which will be on the Christmas Eve of 2024.

Sarah Al-Ahmed: And the timelines I've seen for Parker Solar Probe online usually go till about 2025. Are there any plans for after that 2025 point?

Nour Rawafi: The spacecraft, knock on wood is, very healthy. The payload is very healthy. So, the expectation... We have to propose for extending the mission, and we will propose for that. I strongly believe that NASA will go for it because Parker Solar Probe is an exceptional mission. It's probably the most successful heliophysics mission that NASA has ever [inaudible 00:45:04]. And what we are learning from Parker Solar Probe, we are actually solving big problems. But on top of that, we're discovering the new ones, new phenomena. So, it's really hard to think that Parker Solar Probe will not continue. We'll propose for it. And just talking about the profile of the mission, we launched in 2018 when the Sun was very quiet, we'll end up the prime mission at solar maximum. Hopefully, we'll extend it to cover the whole solar cycle and go beyond that.

Sarah Al-Ahmed: Well, on this page for this episode of Planetary Radio, I'm going to link to a lot of the other science results that have come out of this and our previous episodes all about switchbacks in the magnetic field and the source of the fast solar wind, all those results. But I cannot wait to see what comes out of all the science from this most recent solar activity. And I'm really hoping NASA extends this mission. Because it deserves it, honestly. And your team should be so proud.

Nour Rawafi: Thank you so much. I think it's not only the team, it's the much larger team who are making the mission so successful. We built the mission, but it's the folks who are out there doing science with it. And particularly young folks who are just coming up, those are the ones who discover all these nice results about the mission. We, the team, we can make the mission a success. The larger community will make the mission a mega success. And that's how Parker Solar Probe is doing.

Sarah Al-Ahmed: Well, thanks so much for joining us Nour, and good luck on all of these upcoming flybys. I know your team is going to crush it.

Nour Rawafi: Thank you so much. It's really pleasure talking to you. Thank you, Sarah.

Sarah Al-Ahmed: If you'd like to learn more about Parker Solar Probe and the Sun, the team at Johns Hopkins Applied Physics Lab teamed up with some tech companies to create the ParkerBot virtual assistant. Unlike other chatbots, ParkerBot only answers with content from vetted sources like NASA websites. So, you know you can trust the results. I'll leave a link to that on this page of Planetary radio as well, just in case you want to ask ParkerBot any of your burning solar questions. Now, let's check in with Dr. Bruce Betts, our chief scientist for What's Up? Hey, Bruce.

Bruce Betts: Hi there Sarah.

Sarah Al-Ahmed: The Sun just blasted off a bunch of flares at the time that we're having this recording because we're nearing solar maximum right now. So, things are getting weird.

Bruce Betts: I guess you could phrase it that way. Yeah, it's certainly an active Sun going more activer.

Sarah Al-Ahmed: I did have a question about this. I'm sure it's a very complicated answer, so we don't have to get too deep into the weeds. The thing that causes the aurora is that these charge particles from the Sun end up getting blasted towards the magnetic poles of our world because they follow those magnetic field lines. But during these major solar storms and things like that, we end up with aurora at way lower latitudes. Why is it that it doesn't just brighten in the north? Why do we see it in other locations?

Bruce Betts: Well, the answer is magnetic fields. With the Sun, everything on the Sun can be explained with the answer, it's because of magnetic fields. Boom, we're done. No, I'll give more. Basically, usually you've got particles coming. We've got solar wind all the time, but that doesn't do a lot. And then you get a solar storm, belches out more material at one time, comes, hits the atmosphere, causes aurora. It hits wherever it hits. The charged particles hit the magnetic field of the Earth and they get directed poleward as you stated. And as you hit with more stuff, you kind of futz with the magnetic field and you expand the auroral oval, which is the place where the particles hit the right part of the atmosphere coming down the magnetic field lines. So, that expands outwards. But it's all tied to having more of this stuff. That was a really clear explanation I think. Sorry.

Sarah Al-Ahmed: I've definitely seen those diagrams though, of charged material coming off of the Sun and then that interacting with the Earth's magnetic field and doing some serious disruption to it. We're very lucky that we have such a strong magnetic dynamo to protect us. Because the Sun is not messing around.

Bruce Betts: No, it's not. And it does affect things. And that's why we want more and more solar storm monitoring. Because flares are the light show basically, but they're often associated with these other things, particularly the CMEs, coronal mass ejections, they're like a big belch of material. And if it comes flying at the Earth, if you have enough, you start damaging potentially satellites, power grids on the surface. It gets gnarly. I think we all remember 1859. That was some crazy, crazy stuff, man. Telegraph operators getting burned, things catching on fire, dogs living with cats. It was nuts because of the largest storm historically. So, we are worried about those things. I wanted to point out, it does other weird stuff too. As we head towards solar maximum, you have more of these particles. There's an interaction, not only with the magnetic field but with the atmosphere. Heating in the atmosphere causing an expansion of the atmosphere. That led to the rapid end of LightSail 2, is the atmosphere came up to meet LightSail 2 more and more. And we were going through more atmosphere and being dragged down. In fact, they're on our website, some of the plots showing correlation between solar activity of this type and the rate at which we started dropping as we left solar minimum and headed off towards solar maximum. And we already were dropping some anyway, which we expected, but it led to the fiery death of LightSail 2. Dun dun dun.

Sarah Al-Ahmed: RIP LightSail. But that means that you could actually potentially elongate the lifetime of a satellite by trying to launch it during a solar minimum.

Bruce Betts: Yes, that is true. Which is harder because you need a bigger rocket and more money. But you launch to higher orbits and you don't have this problem because you get away from the atmosphere. It turns out, even where we were at 700 kilometers above the Earth, there's still enough stuff that if you have a five kilogram spacecraft in a sail the size of a boxing ring, it eventually drags that puppy down. You know what would make you feel better? Random space fact.

Sarah Al-Ahmed: I feel better already.

Bruce Betts: I thought you would. As of now, May 2024, 279 people... What have they done, Sarah? What have they done? 279 people?

Sarah Al-Ahmed: I'm going to guess. Went to space?

Bruce Betts: Went to the International Space Station.

Sarah Al-Ahmed: Whoa.

Bruce Betts: 279 individual people. So, many of them went multiple times. They've been from 22 countries. Mostly, not surprisingly, from the US at 165, followed by Russia with 59, and number three... Anyone? Anyone? Japan, with 11.

Sarah Al-Ahmed: I was either going to go Japan or Canada on that one.

Bruce Betts: Yeah, no, it makes sense. Obviously, there've been a number of ESA astronauts, but they're already multiple countries but once space agency equivalent.

Sarah Al-Ahmed: Gosh, that's so cool.

Bruce Betts: All right. All right everybody, go up there, look up in the night sky and think about the variability of palm trees. Thank you and good night. Some of them are really tall and skinny and some are really big and white. It's wild.

Sarah Al-Ahmed: We've reached the end of this week's episode of Planetary Radio, but we'll be back next week to celebrate Asteroid Day. It's the anniversary of the Tunguska Blast. We've also got an update on the DART mission that smashed into asteroid Dimorphos. If you love the show, you can get Planetary Radio T-shirts at, along with lots of other cool spacey merchandise. Help others discover the passion, beauty and joy of space science and exploration by leaving a review and a rating on platforms like Apple Podcasts and Spotify. Your feedback not only brightens our day, but helps other curious minds find their place in space through Planetary Radio. You can also send us your space thoughts, questions, and poetry at our email at [email protected]. Or if you're a Planetary Society member, leave a comment in the Planetary Radio Space in our member community app. Planetary Radio is produced by The Planetary Society in Pasadena, California, and is made possible by our starry-eyed members. You can join us as we learn more about our star and all of the worlds that orbit it at Mark Hilverda and Rae Paoletta are our associate producers. Andrew Lucas is our audio editor. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. And until next week, ad astra.