Planetary Radio • Dec 07, 2022

Scientist and Hubble Repairman John Grunsfeld

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John Grunsfeld

Board of Directors of The Planetary Society; President and CEO of Endless Frontiers Associates

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Jim Bell

Past President (2008-2020), Board of Directors of The Planetary Society; Professor, School of Earth and Space Exploration, Arizona State University; Principal Investigator, NASA Perseverance rover Mastcam-Z instruments

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Bethany Ehlmann

President, The Planetary Society; Professor of Planetary Science, California Institute of Technology; Director, Keck Institute for Space Studies at Caltech

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Sarah Al-Ahmed

Planetary Radio Host and Producer for The Planetary Society

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

John Grunsfeld didn’t just ride the Space Shuttle into orbit five times. He accumulated two-and-a-half days of spacewalk time as he worked on the Hubble Space Telescope. The former NASA associate administrator returns to Planetary Radio for a very personal conversation with Mat Kaplan. We’ll also attend a screening of the great new documentary, “Goodnight Oppy” about the Mars Exploration Rovers. Sarah Al-Ahmed celebrates the 50th anniversary of the last Apollo moon mission, and Bruce Betts continues that theme with the new space trivia contest.

John Grunsfeld
John Grunsfeld Former astronaut and associate administrator of NASA's Science Mission Directorate, John Grunsfeld in space shuttle Columbia's cargo bay.Image: NASA

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How long in hours and minutes was the longest extra-vehicular activity (EVA) carried out on the surface of the Moon?

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Planetary Radio is 20 Earth years old. Approximately how old is it in Mercury years?


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Question from the November 23, 2022 space trivia contest:

Zeus was Artemis and Apollo’s father in Greek mythology. Who was their mother?


In Greek mythology, Leto was the mother of twins Artemis and Apollo.


Mat Kaplan: Scientist and Hubble Space Telescope repairman, John Grunsfeld, this week on Planetary Radio. Welcome. I'm Mat Kaplan of the Planetary Society with more of the human adventure across our solar system and beyond. Five space shuttle missions, three of which were devoted to fixing or upgrading the Hubble. Chief scientist of NASA and then associate administrator of the agency's science mission directorate, that's John Grunsfeld. Now, he is the newest member of the Planetary Society's Board of Directors. We'll sit down with John for an uplifting, revealing, and personal conversation about his travels, his passion for space and science, and where he thinks we are headed. We'll also head over to a special screening of the new and terrific documentary about Opportunity, the Mars Exploration Rover, and the wonderful team that made it such a success. Sarah Al-Ahmed is moments away from joining me in a tribute to Apollo 17, the last Apollo mission to the moon that has just reached its 50th anniversary. We'll close with a visit to Ancient Greece, where Planetary society chief scientist Bruce Betts will reveal the mother of Artemis, sister of Apollo, and namesake for the mission that is headed back from circling the moon as this week's show is published. If all goes well, the uncrewed Artemis 1 mission will splash down off the coast of my hometown San Diego on December 11. You can read more about Artemis in the December 2nd edition of our free weekly newsletter, The Downlink. It's at, where you'll also find the winners of our best of 2022 campaign. You chose them. Now, you can see and help us celebrate the year's greatest accomplishments in space. Sarah Al-Ahmed is now less than a month from becoming the new host of this show. She is finishing up her work as the Planetary Society's digital community manager. Sarah, welcome back again. As people hear this show, at least as it is published, we are celebrating, maybe lamenting a little bit, the very last of the Apollo missions that made it to the moon, and put humans up there on the surface. Apollo 17, as we speak, they were on their way to the moon 50 years ago today.

Sarah Al-Ahmed: It's weird to really grok the fact that it's been 50 years since humans walked around on the moon. I feel like everybody who's really involved and loving space has thought about, researched these Apollo missions, but when you really put it in that context, I mean, December 7th, 1972 was the last time that we launched an Apollo mission. That's wild.

Mat Kaplan: All right, so first, kudos for perfect use of the word grok, which you don't hear often enough anymore. Second, I couldn't agree more, and it just seems so cosmically, romantically appropriate that here we have Artemis I on its way back from the moon, hopefully headed toward a successful reentry, and the next humans who will make that same trip not to land in 2024, but to go around. I'm really curious talking to you as somebody... I mean, I was around. I was there. I was able to enjoy Apollo 11. You weren't there yet. You weren't here on earth yet.

Sarah Al-Ahmed: I wasn't alive yet, which is wild. It's one of those things where you're so steeped in it that it feels so real to you, but it does take on this mythic quality in my mind. When I was a child, my mom would tell the stories about the Apollo landings and watching people on their black and white TV with her family. I never got sick of those stories. It always made me really happy and very hopeful. It does make me feel a lot better knowing that the Artemis program is now in full swing. We went to Kennedy Space Center to go watch what was going to be the first attempt of the first Artemis launch. It didn't go off as planned, but I remember being there, and having that conversation with other people that were all waiting for that launch. We were all just hoping that Artemis would launch before this anniversary, because it felt like we needed that continuation of lunar exploration to really feel happy about what was going on.

Mat Kaplan: In a few minutes, we are going to be talking with John Grunsfeld, a guy who's been up there five times, though not to the moon, he hoped, but it didn't happen. He's going to talk about the importance of doing science when humans go back to the moon. I'm sure you've been thinking about this as a scientist yourself. I mean, Harrison Schmitt, the only scientist to walk on the moon.

Sarah Al-Ahmed: Right. Isn't that wild? It's really cool that they had a scientist on the moon, and very helpful in that particular case because their landing site had such geologic diversity. In the moment, having a scientist, specifically someone with a PhD in geology, be able to look at the rocks on the ground and be like, "Yes, we need a sample of that one," that's very useful, but very strange in context to think that he was the first one to actually at first and only one to ever walk around on the moon. Hopefully the Artemis program takes us into account, and we have a whole new generation of scientists up there on the moon.

Mat Kaplan: A lot more scientists eagerly waiting for their data right down here on Earth along with the rest of us fans. Sarah, thank you. Great talking to you once again.

Sarah Al-Ahmed: Thanks, Mat.

Mat Kaplan: Here's Planetary Society CEO, Bill Nye, speaking a few weeks ago just before the lights dimmed for a screening of Good Night Oppy.

Bill Nye: These missions were where NASA proved they could do it, or we could do it again. This movie is about missions that changed the world and changed our understanding of Mars. Everybody, also, Mat Kaplan's here, the voice of Planetary Radio. We will have Rob Manning. He is now the chief engineer at JPL. You'll see Rob Manning quite a bit in this movie. Another thing the Planetary Society did was we have a stick to cast a shadow. That way, you can infer the color of the Martian sky, and then get the colors of the camera right. We were in touch with a guy at University of Washington who's not here, Woody Sullivan. He said, "If you're going to have a stick, it should be a sundial. It should have a motto," and so my predecessor, Lou Friedman, came up with the motto, "Two worlds, one son." It has the optimistic message to the future, which was co-written by us and Steve Squyres who's featured, "To those who visit here, we wish a safe journey and the joy of discovery, the JOD." That's all you guys, the joy of discovery. Let's roll that film.

Mat Kaplan: It is a wonderful film produced by some of the best in the business. While it's full of gorgeous images and animation, it's the focus on the team behind the Mars Exploration Rovers that makes the film so affecting. At least two of those team members were with us for the screening. Here's Bill Nye introducing one of them.

Bill Nye: All the pictures on Mars from the panoramic camera were taken by that man right there, Jim Bell, who is a professor at Cornell. Back in the day, he sat in the same office that Carl Sagan sat in the Space Sciences Building.

Mat Kaplan: Jim Bell, let me start with your review of the film.

Jim Bell: Oh man, so many memories come flooding back. I look at all the people that I was working with, and they're so young. There's a couple of pictures of me, and there's like, "Oh my God, I was so young," but it was a young, tight knit, relatively small group of people who put the rovers together, built them and the instruments and all that. Of course, many thousands and thousands of people around the world to make all the parts, and launch them, and then operate them and all that, but it was a tight knit group at JPL and a small number of universities around the world who were doing this. So, it was great to see and relive some of that drama. Even though I know exactly what happened and when it happened, I'm still like, "Oh my gosh, is it going to survive? Oh no, dust storm." We were thinking all that same stuff day to day. I think the film really captured well the surprise of the longevity of these amazing robots and also the relationship, the relationship that humans made with those machines. Of course, the robots aren't exploring. The robots are not exploring Mars. People are exploring using the robots. The robots do what we say. They're only as good as their software as they say, and their equipment, and people built them, but you just get attached to them. How long will they live? How long will they last? You just never know. You just come in and enjoy the pictures every day like we're doing still with Curiosity, more than 10 years on Mars, and Perseverance, a year and a half heading close to two years on Mars. It reminds me to count my blessings, and be happy that every single day, we have a robot on Mars, a spacecraft orbiting the moon, a mission flying to the edge of the solar system and beyond. We're just really lucky. We're really lucky to be able to be living in this amazing time of exploration.

Mat Kaplan: I can't let you go without mentioning that, I think, you got a best selling book, a photo album out of these missions.

Jim Bell: It was the first book that I wrote. It was called Postcards from Mars. When we were getting these pictures back, and I think the film captured this as well, it was like a friend is off having this adventure somewhere, and sending you pictures back, postcards back through the mail. That's how we started thinking of these mosaics and panoramas as postcards. That got me hooked on writing photo-oriented space books, which I just love to do.

Mat Kaplan: Speaking of those pictures, I kept waiting for, "Where are the stills? Where are those beautiful images?" But they were all over this actually, because they were the basis of much of the computer-generated imagery that, I think, we were seeing.

Jim Bell: The filmmakers did a beautiful job of taking the real pictures, and layering 3D over them, and driving the rover through them, and using computer graphics to create scenes that we never saw hovering over the rover while it's driving, looking on the ground, looking back up at the eyes of the rover, looking down, but all the scenery in there is real. That was the real Mars in there, and so, really, it was emotional for me to see the edge of Victoria crater. We really had the rover there, and you realize how dramatic it really was and scary to see it. I think it brought a lot of those stills to life.

Mat Kaplan: All right. Before we finish, you're still busy up there. Perseverance, not just stills. Movies, how's it going?

Jim Bell: Things are going great with Perseverance. As I mentioned, Curiosity, things are going great, some incredibly beautiful and amazing landscapes that rover's exploring. Perseverance, we now have 14 drill samples, core samples in the body of the rover. We still have 20 something more to go, but we're about to put our first cash of those samples down as a backup. In case the mission ends early, they'll be available for the future Mars sampler return lander to pick up. It's just super exciting, Mat, to realize that within a decade, we could all see those rocks with our own eyes, and study them in the laboratory, and put them to the real robust test of science. That's happening right now. It's just happening every day, and it's extremely exciting.

Mat Kaplan: Thank you, Jim. Keep taking those great pictures of Mars.

Jim Bell: I'll do it, Mat. Thank you. Best of luck to you as well.

Mat Kaplan: Jim Bell of Arizona State University is the principal investigator for the Mastcam-Z cameras on Perseverance, the rover that is now collecting samples in Mars's Jezero crater. Here's Bill Nye with another introduction.

Bill Nye: If you watch the movie carefully for just a few moments, you will see our president, Dr. Bethany Ehlmann, who was a young [inaudible 00:12:54] postdoc. You were a postdoc-

Bethany Ehlmann: Undergraduate.

Bill Nye: ... undergraduate.

Bethany Ehlmann: 21.

Mat Kaplan: Bethany, you were there at the start?

Bethany Ehlmann: I was privileged to be there at the start. I was an undergrad at Washington University, and I got connected through one of my professors, Ray Arvidson, to work on the science teams during the first year of operation of Spirit and Opportunity at the Jet Propulsion Laboratory during my senior year.

Mat Kaplan: That's amazing. Now, when we say at the start, I mean what portion of the MER mission?

Bethany Ehlmann: I was able to join actually in 2003 before landing as part of all of the practice orts and sorts operations readiness tests and surface operation readiness test. Everything in NASA has an acronym, but I got to participate in those practice runs where we were driving a rover round in the desert remotely practicing the same things that we're doing on Mars, planning as a science team, sequencing it, uplinking it, and then watching the rover execute what we did, and repeating what we did, like what Opportunity did on Mars for over 5,000 souls.

Mat Kaplan: How cool. You told me before the film started, you were on Mars time. You even had one of those crazy watches that was advancing 40 minutes every day.

Bethany Ehlmann: That's right. I mean, we were living on Mars time. We were... Because these are solar-powered rovers, we, as a science team, were living as a rover on Mars. The Mars day is 24 hours and basically 40 minutes, so it's great. You go into work at 9:00, then 9:40, then 10:20, but then midnight and 12:40 and 1:20. It cycles its way through the day, so it messes with the human circadian rhythm as well. So, we all had special watches that were weighted and adjusted to keep Mars time. Some of us were also part of an experiment to see how humans did living on this non-earth times. We wore these things called act watches that could sense motion, and sense your awakeness and alertness.

Mat Kaplan: This is pre-smart watch.

Bethany Ehlmann: This is pre-smart watch, but we were the human Guinea pigs in terms of how it would be to live and work on Mars time. I have to say, one of the features of having two rovers on Mars that were on opposite sides of the planet is that when you switched from Spirit to Opportunity, it was like taking a plane flight to India because you were basically 12 hours off.

Mat Kaplan: This was almost 20 years ago now.

Bethany Ehlmann: Almost. Almost.

Mat Kaplan: What did that experience mean to you? I mean, now, there, you were an undergraduate. Now, I think it's safe to say a senior member of the solar system exploration community. What did that early experience mean to you?

Bethany Ehlmann: Well, I'm not that old, Mat.

Mat Kaplan: No. No. Certainly not.

Bethany Ehlmann: Solidly, mid-career, early mid-career, early mid-career, the experience was incredibly meaningful to me. It is in fact probably the reason I'm a planetary scientist today. The thrill of being able to go into work in the morning, and know that when you opened up those images, when the downlight came in, that what you were one of the first human beings seeing this new vista on another planet, and you did not know what those images would hold was just extraordinary. I went off after the rovers. I had a master's degree lined up. I did environmental policy and management, but I could not get my thoughts off of Mars. I could not get my thoughts out of that exploration, that joy of discovery and the joy of also working with a team, with a team of people equally devoted to facing the unknown, searching and doing what it takes to get the job done on another planet. It was incredibly exciting and invigorating, and I wanted more of that. That's why I'm a planetary scientist who works on missions today.

Mat Kaplan: I hope you know that when I say senior, I only mean in terms of influence.

Bethany Ehlmann: Gravitas.

Mat Kaplan: Gravitas. I like that.

Bethany Ehlmann: I understand.

Mat Kaplan: What's your review of the film?

Bethany Ehlmann: I think it's an incredible communication of that connection, that connection between human and robot. It's not just robots we send to other planets. These are... It's an extension of us. This is our Spirit on another planet, our exploration and really ourselves. It's a testament to how significant these rovers were in the lives of so many people, but also in the arc of space exploration. How we explore planets was really profoundly influenced by the success of Spirit and Opportunity.

Mat Kaplan: That arc continues.

Bethany Ehlmann: It continues with the Curiosity and Perseverance rovers on the surface today. It continues with Mars sample return. It continues with plans to send rovers and mobile explorers to other planets in the solar system, so the dream goes on.

Mat Kaplan: Thank you, Bethany.

Bethany Ehlmann: Always a pleasure, Mat.

Mat Kaplan: Planetary scientist Bethany Ehlmann of Caltech is the president of the Planetary Society. I can't resist sharing a few more seconds from that screening of Good Night Oppy. Here are some of the youngest people who joined us that night. What school are you from?

Students: Thomas Turkin Middle School.

Mat Kaplan: How'd you like the movie?

Students: It was really good.

Mat Kaplan: Did you start to feel like those robots were people?

Students: Definitely. Definitely.

Mat Kaplan: How did it make you feel about all those people? They did so much work to make those robots to get them to Mars and to do that work. Does that look like a job some of you might want?

Students: It's a hard job. Probably not, but I think it's a very inspiring job to have.

Mat Kaplan: You don't have to work on them to like them.

Students: Totally.

Mat Kaplan: Glad you enjoyed it. Bye-bye.

Students: Thank you. Bye.

Mat Kaplan: A quick break, and then my latest conversation with John Grunsfeld.

Bill Nye: Hi, everybody. Bill Nye here, CEO of the Planetary Society. Everything we do from advocacy for missions that matter, to funding new technology to grants for asteroid hunters, and sharing the wonder of space exploration with the world only happens thanks to friends like you who share our passion for space. When you invest in the Planetary Fund today, a generous member will match your donation up to $100,000. Every dollar you give will go twice as far as we explore the world of our solar system and beyond, defend Earth from the impact of an asteroid or comet, and find life beyond earth by making the search for life a space exploration priority. With you by our side, we'll continue to advocate for missions that matter for years to come. How about powering our work in 2023? Please donate today. Visit Thank you for your generous support, and Happy New Year.

Mat Kaplan: There isn't much I need to say to introduce scientist, astronaut, and former NASA associate administrator, John Grunsfeld. Much of his rich background will come up during the great conversation you're about to hear. I will tell you that he is the recipient of many awards, including NASA's distinguished service medal, and its Constellation Award. John flew his plane into Southern California to attend his first meeting as a member of the Planetary Society's board of directors. It was just before that meeting that he sat down with me in our headquarters studio. John Grunsfeld, welcome to Planetary Radio. Not the first time that you've graced our microphones, but more importantly, I want to welcome you to our little party here at the Planetary Society as our newest board member. Thank you for taking this on.

John Grunsfeld: Well, I'm thrilled. I've been or my family's been a member since the mid-90s, and as an astronaut, when I was selected in 1992, Dan Golden told us we were the class of astronauts that would go to the moon and onto Mars. So, I anticipated not only my vicarious voyages to the planets, but maybe a physical voyage to the moon or Mars. Here we are in 2022, 30 years later, and still, no one has set foot on the moon. We certainly haven't gone to Mars since our Apollo astronauts left in 1972, but it's pretty exciting that we're on the cusp, hopefully, of a new generation of explorers.

Mat Kaplan: Now, if you were implying that the Planetary Society, one reason to be involved with us, is that we want all that stuff to happen, and we are working toward it, then I applaud you for that. But, I hope that that's something that we're helping out with. I'll come back to that move toward the moon and Mars finally. It's like I was welcoming you to the party, but the truth is you're one of the fathers of this feast. I mean, for 40 years or more now, you've been doing this stuff, joined NASA as an astronaut, like you said, in '92, but ran science both as chief scientist and head of the science mission directorate, had an awful lot of influence on things that hopefully have put us on that road to the moon and Mars and so many other things that are going on. I got to call attention though to what everybody does. Five shuttle missions between 1995 and 2009, I counted only nine other human beings who've been to space more than five times. You also spent nearly the equivalent of two and a half days outside in a space suit, which just blows me away. I am so envious.

John Grunsfeld: Doing space walks is really the most amazing thing I've ever done, and the most fun thing to do in space. When you're in your own space suit, keep in mind it's a cloth suit with a backpack, with all of your life support, and just a polycarbonate, a plastic visor between you and the vacuum of the universe. Then you really feel like you're your own spaceship. Of course, looking at the earth is beautiful. For me, working on the Hubble is the ultimate dream as an astrophysicist, and just something that thrilled me intellectually and emotionally.

Mat Kaplan: Three of those trips, three of those five, you got up close and personal with the Hubble Space Telescope, but it's the first one, your first time up there, that I want to have you say something about, because didn't you actually do astronomy with a space telescope while you were on the shuttle?

John Grunsfeld: Well, not while I was on the shuttle, but we did replace the rate sensor units, which are those little gyros on Hubble.

Mat Kaplan: Oh, no, I was thinking of your first trip with the ultraviolet.

John Grunsfeld: Oh, my first trip to space. Well, let me go back to my childhood though-

Mat Kaplan: Sure.

John Grunsfeld: ... which is my first love is science. Of course, I was like any other kid. I loved space and dinosaurs. I grew up in the 1960s when we were sending astronauts to space for the first time. And I was just fascinated by space. I grew up in Chicago. The Museum of Science and Industry there in Chicago was my playground. That just had a very heavy influence on me becoming a physicist and then an astrophysicist. So, when I got my PhD at the University of Chicago, and then came here to Pasadena at Caltech, I thought, "Well, maybe a PhD in physics, and being an astrophysicist, flying my experiments on the space shuttle might be something NASA would be interested in." I applied to NASA to become an astronaut, really to be a science astronaut. That was my goal. No idea whether it would happen or not, but I loved what I was doing. I loved building experiments. I loved exploring space as a scientist. Indeed, I got assigned relatively quickly to a mission to do astronomy and space with ultraviolet telescopes. We had three ultraviolet telescopes on board the space shuttle. In 1990, I was at Mount Palomar observing, using the 60-inch telescope there, neutron stars, and working with a telescope operator, which was great fun. That's what astronomers like to do is go to mountain tops, and spend the night looking at the sky. A little over five years later, March of 1995, I was in space as the telescope operator operating telescopes on behalf of astronomers here on the ground. And one of the most amazing observations that we made, and I was up with Sam Durans at the time, is that we pointed the telescopes at Jupiter and specifically the ultraviolet spectrometer at the moon of Jupiter Io. We could clearly see it in the monitor. We were doing spectroscopy of the volcanoes on Io, and the ultraviolet because as the sulfur goes out, the electrons being accelerated by Jupiter ionize the sulfur, and then we can see the ultraviolet light from that, and get the spectrum. Really just an incredible experience to be on orbit doing astronomy. When I was in high school studying science, and thinking, "I'd like to be an astronaut," it was never a really big driving force of, "Oh, I'm going to make these decisions, and do this and that to become an astronaut," because I just assumed that by the time I was an adult, all astronomers would go to space. Now, they go to mountaintops. In the age of the space shuttle, astronomers will go to space. We'll have orbiting space stations. We may have a telescope on the moon. It turns out not to be that good on an idea, but that didn't happen. That hasn't happened yet. I shouldn't say it didn't happen. It hasn't happened yet, but it did happen for me, and I feel really privileged.

Mat Kaplan: You remind me of something that we talked about last night, because we had dinner with other board members here in Pasadena, very enjoyable dinner. I only wish that we could get to a lot of the other stuff we talked about last night. You talked about how you went to bat for an observatory that put some astronomers above mountain tops at the other end of the visible light spectrum, SOFIA, which of course we've talked about many times on this program and is now no more.

John Grunsfeld: SOFIA, the Stratospheric Observatory for Infrared Astronomy, was a 747 aircraft AND a very big aircraft that we cut a hole in the side of, big hole, with a sliding barn door and a two and a half meter telescope inside. This is the evolution of what was the Kuiper Airborne Observatory to do mid and far infrared astronomy. On the surface of the earth and on mountaintops, we have great observatories, very large telescopes, very capable observatories, but some wavelengths of infrared light just don't make it down to the surface, and so you can't observe them. In this mid-infrared, far infrared region is where a lot of molecules, complex molecules, like the molecules that might have seeded the earth to create life. That's where they give off their light, and so this Stratospheric Observatory for Infrared Astronomy, SOFIA, was built to be able to observe the cosmos in these wavelengths of light that don't make it down to the ground, but you think about riding on an airliner. It's bumpy, and there's turbulence, and so an incredibly complex and amazing system was engineered so that while the airplane is flying, the telescope is superbly stabilized. Again, it's an open door, so the telescope is inside the aircraft, and just outside the skin of the aircraft, air is rushing by at 400 miles an hour. It was designed using computational fluid dynamics and a lot of great intuition so that there would be no turbulence as the air rushes by the door, and you could see the cosmos clearly. It worked great. So, for a couple of decades, we flew the observatory, and unlike a space telescope, SOFIA had the advantage that it lands, and you could change instruments, so you could put a higher resolution spectrometer or a more sensitive detector. So, there were a suite of instruments. It's like Hubble, bringing Hubble to the ground, changing instruments, and putting it back up. Not quite as good. Unfortunately, the other side of flying an aircraft is it uses lots of aviation fuel. The instruments are complex. The technology to stabilize it was complex, and it took a lot longer to work out all the bugs than we expected. The operating cost of the aircraft per year was actually somewhat comparable to the operating cost of a space observatory. So, a number of times in the budgeting process, which is a complex NASA presidential administration, the office manager and budget and Congress, SOFIA would be put on the chopping block. My job as associate administrator was to decide whether it was meritorious or not. I turned to the scientific community, and asked them, "Is this something that we want to spend the money on?" The astronomers who are using it resoundingly said, "Yes, of course." We balanced it against other priorities, and I was able to convince the administration, office of management and budget, that we should keep it in the budget, and not cancel it. In one case, I wasn't successful, but fortunately, the scientific community got together, and our international partner, the German Space Agency, was able to work with Congress to make sure that it was funded from the congressional side, and we continued it. But this year, it actually was put on the chopping block again, actually last year, government fiscal year. There was a review done, and it was decided with the upcoming James Webspace telescope, which launched, that enough of the science would be covered by other observatories' ground-based infrared and then James Webspace telescope to not spend money on SOFIA, and so it's been permanently grounded as far as we know. Now, personally, my science right now is observing Europa, the next moon out from IO, with the Hubble Space Telescope collaboration with Bill Sparks and others. Bill is at Study Institute now. We had a Europa observing program with SOFIA. I got to fly twice as an astronomer observing Europa around Jupiter, which was very comparable to my space shuttle experience, observing Jupiter with the ultraviolet telescopes. We had a third observation scheduled for this October, which got canceled with the observatory. So, I'm personally disappointed, but it had a great run. A lot of great science came out of SOFIA.

Mat Kaplan: You're one of those disappointed astronomers when that happened.

John Grunsfeld: Yes, one of many.

Mat Kaplan: That great airborne observatory now grounded. You mentioned JWST. I'm thinking of a talk that you gave once called Hugging Hubble. Which is more huggable, Hubble or JWST?

John Grunsfeld: Well, Hubble is definitely more huggable and has a much more remarkable story. In the end, great science like great literature is all about the story and film, right? If a film has amazing computer graphics, but a lousy story, it's not going to excite people. Hubble's story started like many others like the James Webb Space Telescope story with trials and tribulations and technical difficulties, and cost overruns, and cancellation reviews, and congressional review, and then finally a spectacular launch. In the case of James Webb Space Telescope, the storyline is we don't know if this thing is going to deploy, right?

Mat Kaplan: Yes.

John Grunsfeld: Because it's so extraordinarily complex, and if one little bolt was wrong, or one little wire was the wrong tension, the whole thing won't work. There were hundreds of sequential miracles that had to occur where people had to do their job exactly right. The engineers had to design them right for it to deploy properly. Then we had to make sure it would focus and all that kind of thing. It couldn't be tested on the ground. It's too big and too complex. Now, every individual element we tested, but it all worked spectacularly, and the science already is phenomenal.

Mat Kaplan: Absolutely.

John Grunsfeld: That's the storyline there, but Hubble wasn't quite like that. We had all the same issues. We had to have a space shuttle launch it. We had the crew deploy it. There was drama because the solar ray didn't deploy right. We almost had a space walk to go out and try and manually deploy, but finally, we deployed the Hubble, great fanfare on the ground. Weeks later, astronomers crowded around to monitor to see that first image called first light. It was lousy. I mean, folks who were there-

Mat Kaplan: I can laugh now.

John Grunsfeld: We can all laugh now. The astronomers there knew that they were being filmed by NASA and the networks, and this was a big deal, multi-billion dollar telescope. They cheered, but inside, they were going, "There's something seriously wrong with this telescope. There was something seriously wrong. The mirror was ground super smooth, the best mirror ever made, but to the wrong shape slightly. So, suddenly, the whole future of NASA was actually at risk. People said, "Well, if NASA can't build a telescope, how are they ever going to build a big space station, and go to the moon and Mars and beyond?" NASA's really lost it. So, repairing the telescope, the underdog, the Hubble became the mission for NASA. just like a good western, women and men in white suits, instead of white hats, rode to the rescue on the space shuttle to put in corrective optics, which engineers had devised to fix the telescope. Once those were installed on STS-61 in 1993, the first images came back, and they were even better than anybody ever expected from the Hubble. The rest is history. That Hubble has now become probably the most productive scientific instrument ever created by humans in terms of the breadth and depth of the images. Even more importantly, the Hubble Space Telescope has now given us a high definition view of the universe to show that the sky isn't just a lot of points of light and fuzzy objects. It's actually got great beauty. If we think about a picture of the Orion Nebula, which is the middle star in Orion's Sword in the Constellation Orion, it's an incredible place where gas and dust are collapsing to form baby stars. It's still in nursery. But when you look at the Hubble image, it looks like just incredible art, and we're seeing the universe with the clarity that our human eyes see our environment here on earth. Now, Hubble has given us that view, and the James Webb Space Telescope as well with the kind of clarity that we see our own planet. The universe is a beautiful place.

Mat Kaplan: You've now touched on a constantly recurring theme of this show. It's that phrase that our boss, the guy that you are the boss of, our CEO, Bill Nye, likes to call the PB&J, the passion, beauty, and joy of space exploration and space science. It sounds like that is a lot of what has driven you as well. The last time you and I talked was on the day that Cassini-Huygens ended. I think I talked to you at JPL. Earlier that morning, very early in the morning, I had been at Caltech, and there was another chief scientist of NASA there, former chief scientist of NASA. Both of you, you and Ellen Stofan, became very emotional because of what this mission had meant to you. In that, you were just representing thousands of other people, of course. That emotional side, that appreciation for what this is accomplishing for humanity, does that drive a lot of why you do what you do?

John Grunsfeld: I think it does. There's no question that... This is true for so many planetary scientists, but it's not about fame. It's the passion. It's the discovery. At NASA, we always try and come up with... Every new administrator wants to shepherd some pithy saying that NASA is supposed to do. They're usually quite long, and I can never remember what they are. So, I came up with my own, which is what I think NASA's really all about. It could apply to many other things, but NASA innovates. We create new technology that allows us to go out and explore, and we explore the universe. We explore the earth. We explore the earth moon system, our solar system, the sun, the cosmos. When we explore, we discover things. I truly believe that one of the unique characteristics about humans, most humans, is, I think, that there is some gene or combination of genes that encodes our drive to want to discover things. When we discover things, it gives us great joy. It's a combination of all of our senses, our intellect, probably our biome in some way, but we just get great joy in discovery. For NASA, when we discover things and share that with the public, we inspire the world. So, innovate, explore, discover, and inspire is the credo that I live by.

Mat Kaplan: That's not far off from our mission here at the Planetary Society. I don't want to sound too self-serving here, but there is some serendipity there, I think.

John Grunsfeld: That's why I'm really pleased to join the board.

Mat Kaplan: Well, and I should say that I know everybody on the board, and certainly all of us on the staff are thrilled to have you joining this organization this way. I do want to go back to Hubble, because after all, you were up there three times, both fixing it and upgrading it. To do that as an astronomer and knowing what that was going to mean to your fellow astronomers down here on the surface, that also had to be pretty special.

John Grunsfeld: There's no question. Now, personality-wise, going back again to my youth, in roughly junior high school, a friend and I would play Star Trek. We'd be fighting off some threat.

Mat Kaplan: Cling on to the doubt.

John Grunsfeld: He was always Captain Kirk by his own desire. I was always Mr. Spock, because that was my personality. I tried to live that way, emotionless and analytical. But when I got up to the Hubble very first time, so this is December 1999, my first space walk, my approach to flying in space is really to try and be as professional as possible, as analytical. I'm not into a lot of the touchy-feely human side of space light, especially when I was approaching the space walks, because there's a very tight timeline. You can only be outside for a certain amount of time, because that's how much oxygen and power you have in the space suit. We had just an enormous amount of work to do to get the Hubble back online.

Mat Kaplan: I have to say, this sounds like what you hear from the Apollo astronauts on the moon. Magnificent desolation, but they had a lot of work to get done.

John Grunsfeld: Right, and they didn't want to screw up. I did have that pressure that my first space walk, I didn't want to break the Hubble. That's the mantra is, "Let's fix the Hubble. Don't break the Hubble," because it is a delicate telescope after all, and we wanted to get all the work done. So, getting out of the airlock, getting onto the robotic arm, getting Hubble set up, changing the gyros, all of that was first and foremost in my mind, so much so that after the flight, I asked the medical doctors to send me a copy of my EKG, because we record that so that I could see what happened to my heart rate when for the very first time, I went out of the airlock into the vacuum of space to see what my reaction was. I had to give them the time that I exited, because when they looked at the EKG, they could find no change.

Mat Kaplan: Oh my, wow.

John Grunsfeld: So, I was so focused on just doing the job based on my training that there wasn't a big surge of emotion. That's what I remembered that there was no surge of emotion. It was just business except, about, I think, 20 or 30 minutes into the space walk, we call them EVAs, extra vehicular activity. I was on the end of the arm, and Jean-François Clervoy, European Space Agency astronaut was driving me on the arm. I was about a meter, a little over three feet away, from the telescope. Suddenly, it hit me that I was out in space in a spacesuit, and here for real, not the mockup that I was used to in the training, but the real Hubble Space Telescope. I looked up at it, and it's just glorious. So, for that one moment, I reached out with my arm and my index finger in this big bulky hockey glove, and touched the Hubble just saying, even though I knew it was real, but I just thought, "I'm going to just touch it like that just to make sure this is a real experience." Then I flipped back into my, "Let's get the job done mode," but that moment really sticks in my mind as something where I was like, "I'm going to be a human for five seconds, not a Vulcan."

Mat Kaplan: I'd be disappointed if you hadn't had a few moments like that. As we talk, Artemis 1 is circling the moon in an odd orbit. The first humans in 50 years might do the same in a couple years, 2024, if all goes well. This is all great in my mind. But as an astronomer and somebody who ran science for NASA, what's the role of science as we move toward putting that first woman and next man on the moon?

John Grunsfeld: Well, I do have an opinion on this. In fact, we just finished, well, to be the, I think, 2023 to 2032 Planetary Science Decadal Survey of the National Academies. There's a whole chapter on the role of human exploration. I was with Jen Heldmann, who's from Ames Research Center, and I chaired that chapter. It's an interesting read, and it's very different from the previous Decadal. Every 10 years, we do these surveys of the science, and recommend to the science community what we think the funders should fund.

Mat Kaplan: We've talked about it several times more on the robotic side.

John Grunsfeld: That's right, and so in the previous ones, the prognosis for humans on the moon or Mars was so dismal that the emphasis was there's really no role for humans in planetary science. We need to focus on the robotic missions. But with the Artemis program, and with the hopefully likelihood that we have human explorers on the moon and a potential for human explorers on Mars sooner than later, meaning maybe in 20 years, we always say 20 years. But we took a different tack, which was to say, "On earth, geologists, planetary scientists, they happen to be earth, are incredibly productive. So, what are the high priority science objectives that we should do when we have humans? How should that affect the planning for future missions?" Unfortunately, the way that Artemis was approached in the previous presidential administration is it's all about putting boots on the moon, and some economic zone. Science was pretty much left out of the planning. We said, "You really ought to have science in one of the driver's seats for what we will do. Because if you think about NASA and the great human space flight exploits, you can pretty quickly, in the general public, get an assessment of what people know about NASA." So if you say, do you like NASA? Most Americans say, "We love NASA."

Mat Kaplan: Everybody wears it on their shirt now.

John Grunsfeld: That's right. I love that. In fact, that's true around the world that you see NASA shirts. Then you say, "Well, what do you like about... What are the greatest exploits of NASA?" People will typically say, "Well..." Sometime they'll say, "Louis Armstrong landed on the moon." Well, Neil Armstrong, close, and Buzz Aldrin. We had those lunar exploits, and they'll say, "And the Hubble Space Telescope. Oh, and the rovers on Mars." That's about it. At that point, you run out, and there's nothing about the International Space Station. In fact, one survey not too long ago, more than half of Americans don't know we have an International Space Station.

Mat Kaplan: Well, that's depressing.

John Grunsfeld: That's pretty depressing, but it even gets worse if you ask people who do know about it. "Well, what do we do on the station?" Nobody knows. But the science, people cite Hubble. They cite the deep field. They cite the rovers. They may not know what the rovers do. They cite the ingenuity helicopter now is one of the really exciting things. That was a tech demonstration that, by almost all measures, was not going to fly on Mars because of lack of imagination.

Mat Kaplan: Just in passing, because we'll have to tell this story another time, one that you've fought for.

John Grunsfeld: Absolutely. I thought it was just a brilliant idea. I called it a Mars hack, and that's something that we really had to do. Unfortunately, I was in a position where I could make that happen. It's been spectacular. I think we'll have a lot of utility both for Mars sample-return, but also for learning about how to fly helicopters in very thin air, which is what rescue helicopters have to do in places like Pakistan, Afghanistan, Nepal-

Mat Kaplan: Denali, something you've climbed.

John Grunsfeld: ... Alaska, where we have to do disaster relief or high altitude rescues. I think eventually, some of this technology will come back to Earth. But back to the public perception, people usually gravitate towards knowing about NASA because of the scientific discoveries. So, I think as we move people out from earth, we should follow the classic exploration, which is make sure science is integral to the planning process early on, so the astronauts have at least the potential to do great planetary science. If we think about the voyage of the Beagle, a ship that explored throughout the world-

Mat Kaplan: The one that carried Darwin to the Galapagos.

John Grunsfeld: Nobody remembers what the purpose of the Beagle was, but everyone remembers that that was the ship that carried Darwin to the Galapagos. It was the science. He was just an incidental scientist aboard. For classic exploration of that time, we remember the science, and so let's leverage that. Let's take advantage of our astronauts going to the moon to do great planetary science to discover whether there are volatiles on the moon. We still haven't touched ice on the moon. We don't know for sure that that's ice, or what form it takes, or whether it's accessible, yet we're planning ice processing plants.

Mat Kaplan: That's true.

John Grunsfeld: As the purpose for going, I think we have it backwards.

Mat Kaplan: 20 years maybe, still, like you said, it's what we always say. Are we going to go on to Mars, and do science there, humans that is?

John Grunsfeld: I'm convinced that we will send science to Mars. I do believe that we should demonstrate that we can become a multi-planet species eventually. I think that goes back to that human genome. That's our desire. There are folks who have claimed anyway to have identified gene expression, which drives people to explore. There are some people who are homebodies. They're happy to stay on planet earth forever. They're happy to live in a little house on a hill with a nice view, and not go explore. There are some people like me that have wanderlust. I always want to go somewhere, see new things. When I hike, I'll say, "Okay, I'm going to turn around at noon, and go back to the trail head." Noon comes around, and I say, "Well, I really want to go a little further, see what's around that next bend."

Mat Kaplan: Yes.

John Grunsfeld: That's what drives me, and I think that's what drives humanity. I think we will leave planet earth. Mars is a very hard place to survive, will be a very hard place to survive for humans, but people said that about earth's orbit too. I think we thrive there. We have challenges, and we will address the challenges on Mars, and find a way to live there eventually. It doesn't have to be independent. As long as we still have an earth and a transportation system, we can exchange things. I think the first Martians will be scientists, will be planetary scientists to go out and explore.

Mat Kaplan: I hope so. Just very briefly, looking forward to getting those rocks back sample return.

John Grunsfeld: Absolutely. I'm interested in getting the rocks back. When we planned the Perseverance rover with the sampling system, I would joke, "We'll get the rocks back when people land on Mars and pick them up and bring them home." I hope it's much sooner than that. Caching the samples on Mars was a risk, is a risk, but I think we'll have them back in about a decade.

Mat Kaplan: I want to go back to your start, which was as a high energy astronomer studying those really powerful sources of energy across our cosmos, but then you picked up this big interest in exoplanets, which obviously is a big interest of ours here at the Planetary Society as well. Is that fair? I mean, how excited are you to see new worlds being discovered pretty much every day?

John Grunsfeld: When I was 12 years old, I would lay out on the grass in Chicago, in the suburbs, and look up at the sky, points of light and a few planets, and really wonder whether there were solar systems around those stars. At that time, there was a lot of debate. In a typically human-centric view, there were plenty of scientists and others who said, our solar system is unique. We are special. Solar systems are exceedingly rare. They're very hard to create, and they must be one in a billion chance. Now, if we're only one in a billion, there would still be plenty of solar systems just in our own galaxy-

Mat Kaplan: It's a big galaxy.

John Grunsfeld: ... but it would be numbered in the hundreds, not billions. Like any Copernican revolution, it turns out that solar systems are pretty much around every single star, that when stars form, solar system forms as well. It's just so exciting that we have missions like Kepler, Transiting Exoplanet Survey, Satellite, James Webb Space Telescope that now can do spectroscopy that can look at the atmosphere of a planet around nearby stars. The reason why that's exciting is one is an astronomer, but more importantly, in the search for life beyond earth. The next great revolution is when we find out if we're alone or not. We have no idea what the probability is that life can start on a planet. All we know is we have life here. To me, emotionally, the most likely case is life should be common. Now, it may only be microbial life, but the fact that we're here, and that life started on earth roughly four billion years ago, which is very early means it can't be that hard, but scientifically, we don't know, and until we have a second example. That's why I'm studying Europa, but we may get a glimpse by looking at the atmosphere of planets around nearby stars. Maybe not James Webb, maybe James Webb, but certainly the next generation of telescope after James Webb will have the capability to do high-resolution spectroscopy of the atmospheres of rocky planets about the size of earth around nearby stars, essentially to be a life detective for earths beyond our solar system. So, hopefully in the next couple of decades, we may have an answer as to whether we're alone or not, not to mention Mars, Europa, we have Europa Clipper. In about eight years, we'll have Europa Clipper around Europa doing low passes, which may be able to detect organics in the way that Cassini detected organics in Enceladus. We could have independent life somewhere in our own solar system. It's just the human ingenuity to go and find out, and we're in that generation.

Mat Kaplan: I keep thinking to myself as you talk about these different missions and efforts that are underway, you're not just another fan like I am, like so many people who listen to this show. You are actually for years in the position to move us in the direction that we, I hope, are going to continue in. I hope that that's something that is very gratifying for you. I also hope that you have that sense that as a part of the planetary society, that that'll be an effort that you'll be continuing through us.

John Grunsfeld: Well, certainly, I'm very gratified that I was in the driver's seat to be able to create the perseverance rover, the Ingenuity helicopter, the Europa Clipper, shepherd James Webb to delivery to Northrop Grumman, keep the Hubble Space Telescope going, and a bunch of other missions including our studies here on planet earth, but I'm just one cog in a big wheel. Ed Weiler before me was a fantastic steward of NASA science, and Thomas Zurbuchen after me has just done a tremendous job. I look at his selection of dragonfly to go to Titan. That is the Saturn hack, if you will, equivalent of the Ingenuity helicopter. But whereas Ingenuity was just a technology demonstration, dragonfly has a very capable mass spectrometer, and we're going to fly around and study organics on Titan. Really incredible to think about flying a drone on another world.

Mat Kaplan: I'm going to take you back to Chicago one more time, back when you were going to the Museum of Science and Industry, and laying there under the stars. For me, it was... Well, now it would be the California Science Center, but we had a Museum of Science and Industry in LA, and the Griffith Observatory. I always give them credit. You had an interesting family connection to another shrine of science and sharing science with the public in Chicago. Do you know the one I'm talking about?

John Grunsfeld: Yep. In 1929, a fellow named Adler recruited my grandfather who was an Chicago architect, Ernest Alton Grunsfeld, to go with him to Germany. They went on a steamship to Germany to the Zeiss factory, because they had come up with a machine that could project the stars on a dome. They went over there and looked at it. Adler commissioned my grandfather to design the first planetarium in the Western Hemisphere, which is now called the Adler Planetarium in Chicago. My grandfather designed that, and they built it in... I think they finished in 1931 if I remember correctly. So as a kid, I got to see the Adler Planetarium, and see the star shows, and a little plaque with my grandfather's name, certainly had some influence on my life. But more importantly, when I was in high school, I was admitted into a program called the Astro Science Workshop, which was for high school students to learn basic college astronomy. I went every Saturday for the school year, and learned astronomy. That was my first astronomy course. They recruited graduate students and postdocs from nearby universities. There was one postdoc in particular from Northwestern University named Ed Weiler.

Mat Kaplan: Oh my.

John Grunsfeld: He was one of my teaching assistants for that. Then we were in contact, of course, when I was an astronaut, and he was at NASA headquarters because he was the Hubble project scientist. Then he became the associate administrator, which for science, which was then the job that I followed him in. So, we have a very tight connection there. One of the other high school students with me was a woman named Laura Danly, who went on to get her doctorate in astronomy, and is now at the Griffith Observatory as a senior astronomer.

Mat Kaplan: I'll only say she recently retired from Griffith. Good friend, terrific person, wonderful science communicator as well. You have a board meeting to get into that I may be keeping you from. I got one other question for you. You're in a good position to share with the rest of us. What movies or television programs get space right, living and working in space?

John Grunsfeld: Well, I won't say Avenue 5.

Mat Kaplan: No.

John Grunsfeld: It's very entertaining.

Mat Kaplan: Yes.

John Grunsfeld: Apollo 13, Tom Hanks, Ron Howard, they definitely got it right. Historically, my understanding is they did a great job. Jim Lovell, who lived it, thinks that they did a good job. Of course, he advised, but they actually shot those scenes on the aircraft that we train for zero G, the so-called vomit comet. So, they had great realism, not only because the actors were actually floating, but because they also got to experience the physiological effects that occur when you're in that environment. That helped the realism, so that's a historical film. I think there are some interesting movies that really are science fiction, but capture some of the spirit of space exploration that I think is realistic. Interstellar is one of those. There is a challenge that people talk about. It'll be great when we have a robust space exploration program in our solar system, and people will go visit Jupiter and Europa. I don't think that's going to happen. Even 2001: A Space Odyssey visit to Jupiter, the radiation environment of Jupiter is just killer for biological systems. Now, Europa's covered in this thick ice shell, so under the ice shell in the ocean, they're protected. I don't know what the actual lifetime of a human is on the surface of Europa, but it's probably measured in minutes.

Mat Kaplan: I think you're right.

John Grunsfeld: Not months or years. That's not a place we will visit. I asked Fred Ordway III, who was the science advisor to Stanley Kubrick for 2001: A Space Odyssey, "Why Jupiter?" He said, "Because the artists who were painting frame by frame the planets weren't confident that they could model and paint the rings of Saturn, and so they moved from Saturn to Jupiter."

Mat Kaplan: Dramatic license, I think that's called.

John Grunsfeld: But I still think 2001: A Space Odyssey is the penultimate space movie, and had... Even though now when we look at, it's a little bit hokey. I think they just got so much right, and if we fast forward maybe another 10 or 20 years, I think we really will see commercial space stations. It's on the drawing boards now. We won't see a Pan Am Clipper, but we'll see something roughly equivalent. We think Dream Chaser from Sierra Space right now is that. We had the space shuttle, which really was the Pan Am Clipper, but not a commercial version. If you look closely at that film, there's all kinds of in-space construction and assembly. That's now a big catch thing in space assembly and manufacturing and a moon base. I think that movie still stands as one of the classics and realistic movies of all time.

Mat Kaplan: I am so with you. On your way out of our little studio here at Planetary Society Headquarters, if you didn't notice them already, take a look at my desk where the Pan Am Clipper is sitting next to the Starship Enterprise, a lot to look forward to. So glad that you are now part of the Planetary Society. I hope that you thoroughly enjoy your time as our newest board member. John Grunsfeld, it has been a great pleasure to talk with you on Planetary Radio.

John Grunsfeld: Well, thank you so much, and thank you so much for all these years of planetary radio. It's really a thrill to be on.

Mat Kaplan: What a pleasure to get to talk to heroes, sit across the table from them. Thank you. Time for What's Up on Planetary Radio. The chief scientist of the Planetary Society has joined us once again. Bruce Betts, hi.

Bruce Betts: Hi. It's so busy, Mat. I'm just going to leap right into it. If you're picking this up right after it comes out, I need to mention that December 7th and 8th, so that night, the moon will occult Mars, pass in front of Mars, as seen from much of North America and Europe. So if that's true, go to, and you can link to the monthly update. You'll find a little map to see if you're actually included. We've also got Mars at opposition. It's finally here, Mat. It's finally here. Mars is as close as it's going to get for a while, a long while, and its orbit to earth. Mars is super bright, and because it's at opposition, opposite side of the earth from the sun... I said that right. It rises around sunset in the east, and sets around sunrise in the west. You also have Jupiter up high in the sky earlier in the evening, and also Saturn as well. Later this month, we'll pick up some other planets, but we'll check back with them because right now, we need to talk Geminid's Meteor shower. Normally, the best meteor shower of the earth measured by meteors per minute or per hour, however you want do it. It peaks December 13th, the night of December 13th/14th, through the 14th, but you've got increased activities several days before and after. During the actual peak, a gibbous moon will wash out a lot of the dimmer meteors, but still, there's enough to make it worthwhile. It often has 100 plus meteors per hour from a dark site without that pesky moon, so you can still pick up some even with poorer conditions.

Mat Kaplan: Last Saturday evening, I conducted a little tour of the solar system slides, and then we went outside with my telescope. Mars and Jupiter were just spectacular. I could see all four of the Galilean moons lined up. It really is just such a great time though. Folks, get out there with a telescope, binoculars, or just your naked eyes, and enjoy the view.

Bruce Betts: Remember, even with just binoculars, if you can hold them steady enough, you can see the four Galilean moons looking like little tiny dots next to Jupiter.

Mat Kaplan: Rest your elbows on something. Find a spot, a wall or a table or a car, or Bruce. Put them on Bruce. Put your arms up on Bruce.

Bruce Betts: One thing I'm not figuratively or literally is stable.

Mat Kaplan: Okay.

Bruce Betts: We move on to random space fact.

Mat Kaplan: No this week in space?

Bruce Betts: I'm combining them. I'm getting wild.

Mat Kaplan: Ah, no wonder. Here, I thought I'd caught you in an error.

Bruce Betts: I hear you've already mentioned the 50th anniversary of Apollo 17's launch.

Mat Kaplan: Indeed.

Bruce Betts: Did you see that launch, Mat?

Mat Kaplan: I did. I saw all of them. Well, not in person, but I watched all of them on TV.

Bruce Betts: I actually saw that. I was in Florida as a wee tyke, and watched the launch start in the hotel room on the TV, and then ran out and looked and watched it go across the sky.

Mat Kaplan: Wow.

Bruce Betts: It's quite a memory. I just, of course, keep doing the older person thing of, "Oh my God, it's been 50 years," but that's not my random space fact. That's just a sad comment on my mental state. Cosmic ray visual phenomenon or light flashes, so when the astronauts went to the moon, particularly when they got outside the magnetosphere, and got into a heavier cosmic ray particle radiation environment, although they didn't know this is why it was causing it, they got flashes that they saw with their eyes closed, particularly when the cabin was dark, or they'd had their eyes closed, and it adjusted. It turns out it's apparently from an interaction of cosmic rays with your eye. It actually occurs in lower earth orbit too, but to a lesser extent with fewer things getting through. But apparently, pretty much all of the Apollo astronauts who went out to the moon had this phenomenon occur.

Mat Kaplan: Kind of creepy actually, and at the same time, kind of romantic that you can enjoy the cosmos even with your eyes closed.

Bruce Betts: Ponder what's going through your head.

Mat Kaplan: Exactly.

Bruce Betts: They actually... With Apollo 16 and 17, they had one of the astronauts on each of them wore this Darth Vader mask-looking thing that had detectors, high energy particle detectors on both sides of their heads, so they try to correlate it.

Mat Kaplan: Science.

Bruce Betts: Science. Shall we move on to the trivia question, and delve into the wild world of mythology?

Mat Kaplan: Absolutely.

Bruce Betts: I asked you, "In Greek mythology, who was the mother of Artemis and Apollo?" Of course, Apollo program went to the Moon. Artemis program going to the moon. Who was their mother? How'd we do, Mat?

Mat Kaplan: It never fails. When you ask a question related to Greek mythology, where the answer is drawn from mythology, we get a huge response. This was no exception to that. Let me provide the answer that came from our poet laureate, Dave Fairchild in Kansas. Zeus's eyes would wander, and his wife did not approve. So, Leto ran from Hera, and it kept her on the move. In labor for Apollo, those nine days did not come soon. She's also mom to Artemis, a goddess of the moon."

Bruce Betts: Nice.

Mat Kaplan: Correct, I hope, Leto?

Bruce Betts: Yes, Leto indeed, the mother of Artemis and Apollo from shacking up with Zeus very temporarily. No shacking up was involved. Go ahead, Mat.

Mat Kaplan: They're a little shacking up, a little trickery as well as we heard from Jade Walker, North Carolina, who said, "Finally, my BA in classics comes in handy." Jade reminded us that Leto's Roman name was Leda, adding, "I guess, Zeus already had a bad rap as the ladies man, because he had to turn into a swan to seduce her."

Bruce Betts: Man, they had some weird stuff.

Mat Kaplan: Oh yeah. They were pretty kinky up there on Olympus.

Bruce Betts: Thank you, classics major.

Mat Kaplan: Here's our winner, and he is a past winner. It's Mike Wright Meyer. Mike won. Well, he points it out here. He says, "I keep forgetting to answer these in the hopes of getting one of those cool rubber asteroids, but the chance to win a paper model of the GMT got me here just in time. Also, happy retirement, Mat. If you keep track, I won once in 2017." Well, Mike, you have won yourself one of those built-it-yourself models of the giant Magellan telescope that we talked about a couple of weeks ago when I visited the Mirror Lab at the University of Arizona. Mike, who's in the state of Washington, thanks for sticking with us, Mike, and congratulations. Edwin King in the UK, "The minor planets, 68 Ledo and 639 Latona, are named for this goddess." Judy Engelsberg in New Jersey, "Fun fact, Artemis had a normal birth, but it took nine days to birth her twin brother, Apollo." Dave Fairchild made reference to that. Get this, Leto enlisted Artemis's help, which had to be a first, so Artemis was just born, and helped with the birth of her twin brother.

Bruce Betts: Hey, you lazy kid, get over here.

Mat Kaplan: Really? It's good to keep them busy. Andy Squires in Virginia, Scott John, I think I have that wrong, in Minnesota got the answer from their mythology, Happy Kids. Sean Kane in Missouri, "Leto got a mention in that Greek mythology based episode of Star Trek, the original series." Finally this from Gene Lewin in Washington, "For Boz Scaggs, Leto shuffled." The spelling varied a bit. Frank Herbert had a Leto show respect when Stilgar spit, but we're looking for another here. Who birthed Artemis and her brother, the goddess of fertility? Yes, Leto was their mother.

Bruce Betts: Cool. I believe it was Mel Powell who pointed out that the L.A. Times... Well, he didn't phrase it this way, but they apparently stole my question for the Sunday crossword after I asked it. Also, one of the listeners pointed out the asteroids named after Leto. I was surprised, and that I think is what explains why there was no moon of Jupiter named after Leto since they've named a lot of them after Jupiter's lovers, Zeus's lovers, but I'm guessing it's because they already have the asteroid name since it was one of the early asteroids that was discovered. Little theoretical trip down naming lane there for you. How about we go to a new question. This is in time, so hours and minutes. How long was the longest EVA, extra vehicular activity, that was carried out on the moon by Apollo astronauts? Go to Get us your entry by-

Mat Kaplan: By Wednesday, December 14 at 8:00 AM Pacific time. Just because of tradition's sake, and because by that time, I will only have... By the time we award this, I will only have two shows left. We'll be in the midst of my second to last show, my penultimate Planetary Radio episode. We're going to give the winner a Planetary Society kick asteroid rubber asteroid.

Bruce Betts: Are you going to sign it, Mat?

Mat Kaplan: I guess we could both sign it. There's room.

Bruce Betts: With the word penultimate.

Mat Kaplan: I think we're done too.

Bruce Betts: All right, everybody, go out there. Look up the night sky, and think about the penultimate thing that you thought of. Thank you and good night.

Mat Kaplan: He's the chief scientist, Bruce Betts, who is the penultimate participant in Planetary Radio every week as we do What's up? Thank you. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its high flying members. Become part of our mission at Mark Hilverda and Rae Paoletta are our associate producers. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad astra.