Can we build permanent human settlements in space? It might be more complex than you think. Kelly and Zach Weinersmith join Planetary Radio this week to discuss their new book, "A City on Mars: Can We Settle Space, Should We Settle Space, and Have We Really Thought This Through?" Then Bruce Betts, the chief scientist of The Planetary Society, and host Sarah Al-Ahmed chat about some of the most significant challenges humanity might face as we build habitats beyond Earth.


Discover more at: https://www.planetary.org/planetary-radio/2023-a-city-on-mars

Can we build permanent human settlements in space? It might be more complex than you think. Kelly and Zach Weinersmith join Planetary Radio this week to discuss their new book, "A City on Mars: Can We Settle Space, Should We Settle Space, and Have We Really Thought This Through?" Then Bruce Betts, the chief scientist of The Planetary Society, and host Sarah Al-Ahmed chat about some of the most significant challenges humanity might face as we build habitats beyond Earth.
 Discover more at: <a href="https://www.planetary.org/planetary-radio/2023-a-city-on-mars">https://www.planetary.org/planetary-radio/2023-a-city-on-mars</a>

Planetary Radio brings you the human adventure across our Solar System and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts who are taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye the Science Guy and Bruce Betts as they dive deep into space science and exploration. The monthly Space Policy Edition takes you inside the DC beltway where the future of the US space program hangs in the balance. Visit planetary.org/radio for an episode guide and much more.

Planetary Radio brings you the human adventure across our Solar System and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts who are taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye the Science Guy and Bruce Betts as they dive deep into space science and exploration. The monthly Space Policy Edition takes you inside the DC beltway where the future of the US space program hangs in the balance. Visit planetary.org/radio for an episode guide and much more.

Planetary Radio: Space Exploration, Astronomy and Science

Planetary Radio brings you the human adventure across our solar system and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye, the Science Guy, and Bruce Betts, chief scientist for The Planetary Society, as they dive deep into the latest space news. The monthly Space Policy Edition takes you inside the DC beltway with Casey Dreier and Jack Kiraly to discuss the politics of space exploration in the US and advocacy actions you can take to support the missions that matter. Visit planetary.org/radio for the space trivia contest, an episode guide, and much more.

Planetary Radio brings you the human adventure across our solar system and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye, the Science Guy, and Bruce Betts, chief scientist for The Planetary Society, as they dive deep into the latest space news. The monthly Space Policy Edition takes you inside the DC beltway with Casey Dreier and Jack Kiraly to discuss the politics of space exploration in the US and advocacy actions you can take to support the missions that matter. Visit planetary.org/radio for the space trivia contest, an episode guide, and much more.

Kelly and Zach Weinersmith join Planetary Radio this week to discuss their new book, "A City on Mars: Can We Settle Space, Should We Settle Space, and Have We Really Thought This Through?"

A City on Mars

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-imap

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&rsquo;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&ndash;Earth L1 Lagrange point, IMAP uses 10 instruments to study the heliosphere &mdash; 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&rsquo;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&rsquo;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:&nbsp;<a href="https://www.planetary.org/planetary-radio/2026-imap">https://www.planetary.org/planetary-radio/2026-imap</a>

Host Sarah Al-Ahmed speaks with David McComas, principal investigator of IMAP and IBEX, and Matina Gkioulidou, IMAP project scientist, about how energetic neutral atoms let us map the heliosphere.

IMAP and the shape of the heliosphere

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-heliopause

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&rsquo;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&rsquo;s protective bubble, and why those measurements have upended earlier ideas about where the Solar System truly ends. Spilker also reflects on the mission&rsquo;s extraordinary longevity, the ingenuity required to keep the spacecraft communicating across the vastness of space, and what Voyager&rsquo;s legacy means for future journeys between the stars.
Then, in What&rsquo;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:&nbsp;<a href="https://www.planetary.org/planetary-radio/2026-voyagers-and-the-heliopause">https://www.planetary.org/planetary-radio/2026-voyagers-and-the-heliopause</a>

Linda Spilker, project scientist for the Voyager mission, explains what Voyager has revealed about the heliopause and the Solar System’s outer edge.

Voyager and the heliopause: Exploring where the Sun gives way to the stars

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-nasa

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, &ldquo;The Challenges of Change at NASA,&rdquo; 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: <a href="https://www.planetary.org/planetary-radio/spe-2025-a-year-of-disruption-and-change-at-nasa">https://www.planetary.org/planetary-radio/spe-2025-a-year-of-disruption-and-change-at-nasa</a>

After DOGE cuts, mass staff departures, and a blink-and-you-missed-it pivot to Mars, how much did NASA actually change in 2025? Space Policy Online founder Marcia Smith returns to assess a turbulent year.

A City on Mars

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