Planetary Radio: Space Exploration, Astronomy and Science

Gentry Lee spent nearly five decades at NASA's Jet Propulsion Laboratory, and in that time he helped shape some of the most ambitious missions in the history of space exploration. A new documentary, “Starman,” chronicles his career and the big question that runs through it: is there life beyond Earth? Lee worked on every NASA mission to land on Mars, helped Carl Sagan bring the Universe to living rooms around the world with “Cosmos,” and oversaw dozens of active missions as Chief Engineer for the Solar System Exploration Directorate at JPL. Few people have had a front-row seat to the Space Age quite like him. In this episode, host Sarah Al-Ahmed sits down with Gentry at Planetary Society headquarters just one day after his retirement from JPL. He reflects on the colleagues who shaped him, the missions that changed our understanding of the Solar System, and why the search for life beyond Earth remains the most profound endeavor humanity has ever undertaken. Discover more at: https://www.planetary.org/planetary-radio/2026-starmanSee omnystudio.com/listener for privacy information.

Is the United States really in a new space race with China? Or is that framing missing the bigger picture? In this Space Policy Edition of Planetary Radio, Casey Dreier, chief of space policy at The Planetary Society, sits down with Patrick Besha, former NASA strategic advisor on China, to explore the realities behind China’s rapidly advancing space program. They discuss how China’s political system shapes its long-term space strategy, why the rhetoric about a “space race” may be misleading, and how competition between the United States and China in space is likely to unfold over the coming decades. Discover more at: https://www.planetary.org/planetary-radio/spe-us-china-space-raceSee omnystudio.com/listener for privacy information.

NASA has announced a major restructuring of the Artemis program, reshaping the roadmap for returning humans to the Moon. At a February 27 press conference, agency leadership addressed the rollback of Artemis II following post–wet–dress–rehearsal testing and unveiled significant changes to upcoming missions, including shifting Artemis III from a planned lunar landing to a low-Earth-orbit rendezvous and integrated systems test. In this episode, you’ll hear remarks from NASA Administrator Jared Isaacman and Lori Glaze, Moon to Mars program manager and acting associate administrator for NASA’s Exploration Systems Development Mission Directorate. They explain what happened with Artemis II and why NASA is changing course. Then, host Sarah Al-Ahmed is joined by Jack Kiraly, director of government relations at The Planetary Society, and Ari Koeppel, AAAS science and technology policy fellow, to unpack the political and strategic forces behind this shift and what it means for the future of lunar exploration. In What’s Up, Bruce Betts, our chief scientist, looks back at Apollo 9, the Earth-orbiting mission that proved the Lunar Module could operate independently before NASA attempted a lunar landing. Discover more at: https://www.planetary.org/planetary-radio/2026-artemis-updateSee omnystudio.com/listener for privacy information.

Could a single ancient impact have briefly transformed one of the Solar System’s darkest moons into a cryovolcanic world? When Voyager 2 flew past Uranus in 1986, it captured the only close-up images we have of Umbriel, a heavily cratered, charcoal-dark satellite long considered geologically inactive. But one feature stands out: a bright ring inside the 131-kilometer-wide Wunda crater. In this episode, Sarah Al-Ahmed speaks with Adeene Denton, NASA postdoctoral program fellow at the Southwest Research Institute, about her team’s new study published in the Journal of Geophysical Research: Planets. Using shock physics simulations, Denton and her colleagues reconstruct the impact that formed Wunda crater to determine what Umbriel’s interior must have been like at the time. Their modeling explores whether impact-induced cryovolcanism can explain the bright deposits observed on the crater floor. Then, in What’s Up, Bruce Betts, chief scientist of The Planetary Society, joins Sarah to break down one of the key mechanisms that keeps icy moons from freezing solid, tidal heating driven by orbital resonance.  Discover more at: https://www.planetary.org/planetary-radio/2026-cryovolcanism-on-umbrielSee omnystudio.com/listener for privacy information.

They informed and entertained together throughout the first 20 years of Planetary Radio. Listen in as the Society’s chief scientist and book club edition host Mat Kaplan share the mic once again for a delightful conversation about Dr. Betts’ two new space books for young people. “Are We Alone?” introduces the search for life across the Universe, while “The Size of Space” collects many of Bruce’s brilliant and hilarious ways to cut our Solar System down to human size. Discover more at: https://www.planetary.org/planetary-radio/book-club-bruce-bettsSee omnystudio.com/listener for privacy information.

This week on Planetary Radio, we mark a major leadership transition at The Planetary Society. Host Sarah Al-Ahmed sits down with Bill Nye, outgoing chief executive officer and newly appointed chief ambassador of The Planetary Society, and Jennifer Vaughn, incoming chief executive officer and former chief operating officer, for a candid conversation about this long-planned transition. Together, Bill and Jenn reflect on how the organization, under their shared leadership, grew into the world’s largest and most effective nonprofit dedicated to advancing the scientific exploration of space. Then, Bruce Betts, chief scientist of The Planetary Society, joins Sarah for What’s Up. They discuss an upcoming planetary alignment on and around February 28, 2026. Discover more at: https://www.planetary.org/planetary-radio/2026-jennifer-vaughn-ceoSee omnystudio.com/listener for privacy information.

Where did Earth’s water come from? In this episode of Planetary Radio, we explore how scientists are answering that question by studying a remarkably well-preserved record of the early Solar System: lunar samples brought back by the Apollo missions. Host Sarah Al-Ahmed is joined by Tony Gargano, postdoctoral fellow at the Lunar and Planetary Institute with the University Space Research Association and a research affiliate at NASA’s Johnson Space Center. Gargano studies lunar rocks and regolith to understand how planets form, evolve, and acquire key ingredients like water over time. By analyzing subtle chemical fingerprints preserved in Apollo-era lunar regolith, his work helps constrain how much water meteorites could have brought to Earth and what that means for our planet’s path to habitability. The episode also features a short bonus segment with actor George Takei, recorded at the Academy Museum of Motion Pictures during a screening of “Star Trek IV: The Voyage Home.” Takei reflects on the enduring legacy of “Star Trek,” its influence on generations of scientists and explorers, and why he is excited about humanity’s return to the Moon in the Artemis era. He connects science fiction’s hopeful vision of the future with the real science helping us understand our origins today. Discover more at: https://www.planetary.org/planetary-radio/2026-earth-water-apollo-moon-dustSee omnystudio.com/listener for privacy information.

What does a NASA authorization bill actually do, and why does it matter? In this episode of Space Policy Edition, we dig into one of the most misunderstood but powerful tools Congress uses to shape the future of U.S. space exploration. Host Casey Dreier, chief of space policy at The Planetary Society, is joined by Jack Kiraly, the Society’s director of government relations, for a deep dive into how NASA authorization bills work, how they differ from appropriations, and why they can have decades-long consequences for science missions, human spaceflight, and planetary defense. The discussion also reflects on a major recent win for space advocates: Congress’s bipartisan decision to protect NASA science funding. Discover more at: https://www.planetary.org/planetary-radio/spe-what-is-a-nasa-authorization-billSee omnystudio.com/listener for privacy information.

What if Europa’s seafloor isn’t alive with activity after all? This week on Planetary Radio, host and producer Sarah Al-Ahmed explores new research that reframes how scientists think about one of the Solar System’s most intriguing ocean worlds. Sarah is joined by Paul Byrne, associate professor of earth, environmental, and planetary sciences at Washington University in St. Louis. Paul is the lead author of a new study suggesting that the seafloor beneath Europa’s global ocean may be geologically quiet today, potentially lacking the hydrothermal activity often associated with habitable environments on Earth. Together, they discuss how scientists investigate places we can’t yet observe directly and why Europa remains a compelling world to explore regardless of what we find. Then, Bruce Betts, chief scientist of The Planetary Society, joins us for What’s Up to explain why Saturn’s moon Enceladus shows strong evidence for active hydrothermal vents beneath its icy crust, offering a fascinating contrast between two ocean worlds. Discover more at: https://www.planetary.org/planetary-radio/2026-europas-quiet-seafloorSee omnystudio.com/listener for privacy information.

Humans are preparing to return to the Moon. On this episode of Planetary Radio, host Sarah Al-Ahmed is joined by Kelsey Young and Noah Petro, two of the scientists helping turn humanity’s return to the Moon into reality. Kelsey Young is a research space scientist at NASA Goddard Space Flight Center and serves as the Artemis Science Flight Operations Lead. She also leads the Lunar Observations and Imaging Campaign for Artemis II, defining what astronauts will observe, document, and study as they fly around the Moon for the first time in more than 50 years. Noah Petro is the lab chief of the Planetary Geology, Geophysics, and Geochemistry Laboratory at NASA Goddard and the former Project Scientist for the Lunar Reconnaissance Orbiter. He also serves as the Project Scientist for Artemis III, helping shape the science behind humanity’s first lunar footsteps of the 21st century. Together, they discuss how Artemis II and Artemis III build on decades of lunar science, how astronauts are being trained to observe the Moon like geologists, and why the Moon’s south pole is such a compelling destination for future exploration. Then, we wrap up with What’s Up, where Bruce Betts, chief scientist of The Planetary Society, shares the story of the first and so far only professional geologist to walk on the Moon. Discover more at: https://www.planetary.org/planetary-radio/2026-artemis-ii-and-iiiSee omnystudio.com/listener for privacy information.

After months of uncertainty, NASA science has been spared from the largest proposed budget cuts in the agency’s history. In this episode of Planetary Radio, host Sarah Al-Ahmed unpacks how Congress moved to restore near-full funding for NASA science and what that victory really means for missions, researchers, and the future of space exploration. Sarah is joined by Jack Kiraly, director of government relations at The Planetary Society, and Ari Koeppel, an AAAS science & technology policy fellow at The Planetary Society, to break down what passed in the FY 2026 budget, why the details matter, and how bipartisan support helped protect science programs across planetary science, astrophysics, Earth science, and heliophysics. The conversation also takes an honest look at the costs of the past year, from lost jobs and disrupted missions to shaken morale, and why rebuilding NASA’s scientific workforce will take time, even after this hard-won win. We also look ahead to what comes next as the FY 2027 budget process begins, and why sustained public engagement remains essential to protecting space science. Plus, Bruce Betts, chief scientist of The Planetary Society, joins us for What’s Up, where we discuss the recent early return of astronauts from the International Space Station, what’s known about the situation, and what it means for station operations. Discover more at: https://www.planetary.org/planetary-radio/2026-nasa-science-savedSee omnystudio.com/listener for privacy information.

Famed astrophysicist and science communicator Adam Frank shares his sense of wonder and humor in a live conversation about his excellent new book, “The Little Book of Aliens.” Join Adam and host Mat Kaplan as they explore the origin of life, the search for extraterrestrial intelligence, and whether all those UFO sightings are worthy of deeper investigation. Discover more at: https://www.planetary.org/planetary-radio/book-club-adam-frankSee omnystudio.com/listener for privacy information.

Our Solar System is wrapped in a vast, invisible bubble created by the Sun, a protective region that shields Earth and the planets from much of the radiation that fills our galaxy. But until recently, scientists have only had rough sketches of what this boundary looks like and how it behaves. In this episode of Planetary Radio, host Sarah Al-Ahmed is joined by David McComas, professor of astrophysical sciences at Princeton University and principal investigator of NASA’s Interstellar Mapping and Acceleration Probe (IMAP) and Interstellar Boundary Explorer (IBEX) missions, along with Matina Gkioulidou, a heliophysicist at Johns Hopkins Applied Physics Laboratory, former IMAP-Ultra instrument lead, and current IMAP project scientist and co-investigator. Now stationed at the Sun–Earth L1 Lagrange point, IMAP uses 10 instruments to study the heliosphere — the region where the solar wind collides with material from interstellar space. The mission does this by tracking energetic neutral atoms, particles that travel in straight lines from distant regions of the heliosphere, allowing scientists to map areas of space that spacecraft can’t directly sample. McComas and Gkioulidou explain how IMAP builds on the legacy of Interstellar Boundary Explorer, what makes this mission different, and why understanding the Sun’s influence across space matters not just for fundamental science, but for space-weather forecasting and protecting technology and astronauts closer to home. Discover more at: https://www.planetary.org/planetary-radio/2026-imapSee omnystudio.com/listener for privacy information.

What does it really mean to enter interstellar space, and what have we learned since humanity first crossed the invisible boundary between our Sun and the stars? In this episode of Planetary Radio, we explore the science of the heliosphere and the realm beyond with Linda Spilker, project scientist for the Voyager mission at NASA Jet Propulsion Laboratory. Drawing on decades of experience with the twin spacecraft, Spilker shares how Voyager reshaped our view of the Solar System’s outer frontier, from the nature of the heliopause to the unexpectedly rich structure of the local interstellar medium. We unpack what Voyager 1 and Voyager 2 have taught us about charged particles, magnetic fields, and cosmic rays beyond the Sun’s protective bubble, and why those measurements have upended earlier ideas about where the Solar System truly ends. Spilker also reflects on the mission’s extraordinary longevity, the ingenuity required to keep the spacecraft communicating across the vastness of space, and what Voyager’s legacy means for future journeys between the stars. Then, in What’s Up, Bruce Betts, chief scientist at The Planetary Society, places Voyager in context, showing how long-lived missions shape the bigger picture of space science and why observing longer can lead to some of our most profound discoveries. Discover more at: https://www.planetary.org/planetary-radio/2026-voyagers-and-the-heliopauseSee omnystudio.com/listener for privacy information.

Marcia Smith, the founder and editor of Space Policy Online, joins the show and revisits a conversation we had one year ago, recorded just weeks before the second Trump administration took office. That episode, “The Challenges of Change at NASA,” explored the institutional and political roadblocks to radical change at the U.S. space agency. A lot has happened since that show, including DOGE, mass staff departures, a draconian budget cut proposal, a dramatic shift toward sending humans to Mars, and the rapid departure of 20% of NASA's workforce. But at the end of the year, much remains the same. The SLS and Orion programs continue unchanged, with funding locked in through 2032. The humans-to-Mars policy has effectively vanished; returning U.S. astronauts to the Moon, to stay, is again centered within civil space policy. NASA's science missions, though still facing a serious budgetary threat, have not gone away. So, did we see real change at NASA? And to what end? Or was it merely disruption masquerading as change? Marcia Smith and host Casey Dreier revisit their original analysis and discuss what they got wrong, what they got right, and what surprised them about 2025 in civil space policy. Discover more at: https://www.planetary.org/planetary-radio/spe-2025-a-year-of-disruption-and-change-at-nasaSee omnystudio.com/listener for privacy information.

As 2025 comes to a close, Planetary Radio looks back on a year that reshaped space exploration, through stunning discoveries, major milestones, unexpected challenges, and the people who carried science forward through it all. In this episode, Sarah Al-Ahmed, host and producer of Planetary Radio, is joined first by Kate Howells, public education specialist at The Planetary Society, to share results from The Planetary Society’s Best of 2025 campaign and the newly released 2025 Year in Pictures edition of The Planetary Report. They discuss the images, missions, and accomplishments voted on by the global space community, and how space imagery continues to inspire curiosity, connection, and hope. Then, Sarah sits down with Mat Kaplan, senior communications advisor, Asa Stahl, science editor, and Ambre Trujillo, digital community manager at The Planetary Society, for a wide-ranging conversation about the defining space exploration stories of 2025.  The episode closes with Bruce Betts, chief scientist of The Planetary Society, in What’s Up, where he looks ahead to what’s coming in 2026. Discover more at: https://www.planetary.org/planetary-radio/2025-looking-back-space-explorationSee omnystudio.com/listener for privacy information.

2025 was one of the most consequential years for space policy in modern U.S. history. In this special year-in-review episode, Planetary Radio takes a deep dive into what happened behind the scenes in U.S. space policy and advocacy as NASA faced unprecedented proposed cuts to its science programs. With nearly half of NASA’s science budget at risk, dozens of missions threatened, and months of leadership uncertainty at the agency, this year became a defining moment for the future of space science. Sarah Al-Ahmed is joined by Casey Dreier, chief of space policy at The Planetary Society, Jack Kiraly, director of government relations, and Ari Koeppel, an AAAS science & technology policy fellow, to unpack how this crisis unfolded and how scientists, space advocates, and lawmakers responded. Together, they explore how public advocacy helped shift the conversation in Congress. Plus, in What’s Up, Chief Scientist Bruce Betts explains why stability matters so much for space science and what’s at stake when long-term missions are disrupted. This is the first of two special year-end episodes. Next week, Planetary Radio will look back at what humanity accomplished in space exploration in 2025, from new missions and discoveries to milestones across our Solar System and beyond. Discover more at: https://www.planetary.org/planetary-radio/2025-looking-back-space-policy-and-advocacySee omnystudio.com/listener for privacy information.

It was such a delight to feature work by our own Kate Howells in The Planetary Society’s member book club. We keep Kate busy as our public education specialist, but she found time to write about many of her favorite natural satellites in this richly illustrated edition. Join her and book club host Mat Kaplan for a journey taking us from our own Moon, past Europa, Titan, and many more, and out across a galaxy that is no doubt full of worlds circling other worlds.  Discover more at: https://www.planetary.org/planetary-radio/book-club-kate-howellsSee omnystudio.com/listener for privacy information.

Thirty years ago, NASA’s Galileo spacecraft became the first mission to orbit Jupiter, opening a new chapter in our exploration of the outer Solar System. Over eight years around Jupiter, Galileo transformed how we understand Jupiter and its moons, revealing a powerful and dynamic planetary system, uncovering evidence for oceans hidden beneath icy worlds, and reshaping the search for life beyond Earth. To mark the 30th anniversary of Galileo’s orbital insertion, scientists, engineers, historians, and advocates gathered at the California Institute of Technology for a special symposium: Galileo at 30. In this episode of Planetary Radio, host Sarah Al-Ahmed takes you inside that celebration. You’ll hear how Galileo survived seemingly impossible challenges, how its team adapted when things went wrong, and how its discoveries reshaped planetary science. You’ll hear from key voices in Galileo’s story, including historian Erik Conway, project manager Bill O’Neil, magnetometer principal investigator Margaret Kivelson, Europa Clipper Project Scientist Bob Pappalardo, and Dragonfly mission Principal Investigator Elizabeth “Zibi” Turtle, along with reflections from many others whose lives and careers were shaped by this remarkable mission. Together, they tell the story of Galileo not just as a spacecraft, but as a shared human effort, one whose legacy continues to guide exploration today. Discover more at: https://www.planetary.org/planetary-radio/2025-galileo-at-30See omnystudio.com/listener for privacy information.

Why do we explore space, and why does science matter in the first place? In this Space Policy Edition rerun, Planetary Society Chief of Space Policy Casey Dreier revisits a deeply influential 2020 conversation with philosopher and ethicist J. S. Johnson-Schwartz, author of The Value of Science and Space Exploration. As debates over NASA’s budget and the future of space science continue to resurface, this conversation remains strikingly relevant. Dr. Johnson Schwartz makes a compelling philosophical case that science itself is not merely useful or beneficial, but a moral obligation. Beyond economic returns, technological spinoffs, or national prestige, the pursuit of knowledge has intrinsic value, and public space agencies play a critical role in representing that shared human interest. Discover more at: https://www.planetary.org/planetary-radio/the-moral-case-for-spaceSee omnystudio.com/listener for privacy information.