Podcast Summary

Podcast: New Books Network
Episode: Dagomar Degroot, "Ripples on the Cosmic Ocean: An Environmental History of Our Place in the Solar System"
Host: Gregory McNiff
Guest: Dagomar Degroot, Associate Professor of Environmental History, Georgetown University
Publication: January 13, 2026

Overview

This episode explores Dagomar Degroot’s provocative new book, Ripples on the Cosmic Ocean: An Environmental History of Our Place in the Solar System. Degroot argues that our solar system is not just a scientific backdrop but an environment that has deeply shaped, and been shaped by, human history. The conversation ranges widely between existential risks, the unintended consequences of space exploration, planetary history, and the urgent need for more democratic, forward-thinking stewardship of Earth and its cosmic neighborhood.

1. Origin and Motivation for the Book

• Degroot’s Motivation

  • Written partly as a response to personal despair over climate change. Degroot had previously focused on Earth-bound threats but wanted to seek a broader, more uplifting narrative—yet found the project led him to also confront existential and cosmic risks as central themes.
  • Quote:

    "I wanted to write a book that was a little bit more uplifting and that provided new historical perspectives on things that I hope would go well in the coming century… Trouble was, maybe it's just my personality, but Ripples on the Cosmic Ocean ended up being a book in part also about existential risk." (03:16)

• Target Audience

  • Anyone interested in the intersection between environmental history, space science, and humanity’s future—scholars, policymakers, and the curious, “space nuts.”

2. What is Environmental History?

[05:12]

• Definition:
  • Environmental history is the study of “the mutual interactions between environments and peoples through time.” It treats human history as fundamentally embedded in and shaped by non-human forces—extending that lens beyond Earth itself in this book.
  • The “cosmic ocean” is a metaphor for the interconnected, ever-changing solar system of which Earth is only a single, vulnerable component.

    "The changes I look at in ripples are those changes that are not cyclical, that are kind of anomalous. We don't expect them, just sort of happen. And partly because we don't expect them, they have a big impact on us historically." (06:46)

3. Should Humans Alter Environments Beyond Earth?

[07:38–13:55]

• Moral and Strategic Dilemmas
  • Humanity is approaching the capacity to intentionally transform environments off-Earth—the Moon, Mars, near-Earth space.
  • Multiple visions exist:
    • Technological: The Kardashev Scale (harnessing planetary, then stellar, then galactic energy).
    • Ethical: Is it immoral to extractively transform other environments? Or is it justified if the goal is to preserve Earth?
  • Degroot’s nuanced stance:

    "Earth's environments are uniquely valuable in the solar system. And I think that if you can transform the moon's environment to preserve environments on Earth… then I would support that." (11:04)

  • Rejects a simplistic “go back to nature” solution, noting that Earth’s resources are finite; offworlding resource extraction or energy generation may be preferable to continued pressure on Earth.

4. Human Actions Ripple Through the Solar System

[13:55–18:14]

• Direct and Indirect Impacts

  • Activities on Earth can affect lunar and Martian environments (e.g., landing craft altering the Moon’s tenuous exosphere; contamination concerns with Mars and Venus missions).
  • Forward contamination: Earth’s microbes may already have been transferred to other worlds despite sterilization protocols.

    "There's a real chance that we've brought viable microbial communities to other planets. And if that's the case, that could have been planet altering…" (15:41)

• Back (Reverse) Contamination

  • Returning material or organisms from space may also threaten Earth’s environment.
  • The Apollo program’s ambiguous and possibly flawed quarantine procedures are presented as a sobering case study.

    "It is possible that there are microbes lurking in the solar system that, when brought back to Earth, would cause a real problem. That is a possibility, and it's an unknowable possibility." (21:26)

• Existential Risks

  • Example: If “mirror life” with reversed chirality from, say, Europa, came to Earth, our immune systems might not be able to check its spread.

    “If we bring that water from Europa to Earth and it's got microbes in it, and the microbes escape containment, then we don't know what's going to happen.” (24:22)

5. Power and Policy: Who Decides What Happens in Space?

[25:15–33:49]

• Lack of Democratic Oversight

  • Decisions about space—often involving risks to all humanity—are made predominantly by militaries, corporations, and great powers (historically the U.S., USSR/Russia, China).
  • Quote:

    “We lack the ability to have transparent and democratic inclusive conversations about the risks that we now face and how to mitigate them as a species… There's a philosopher called Toby Ord who argues that we’re living through something he calls the precipice…” (27:29)

• Possible Solutions and Limits

  • Could we build a “space UN”? Degroot is uncertain, pointing to historic successes (e.g., Montreal Protocol) but also to present-day global fragmentation.
  • Raises specter of a “global hegemon” as an alternative, which brings its own risks.

    “The way the world is going right now, of course, again, is not in the right direction… It doesn't leave me optimistic for the short term future.” (33:49)

6. Book Structure: The Five Parts

1. The Sun

[33:49–43:53]

• Absolute Environmental Centrality
  • Everything on Earth derives ultimately from the Sun’s energy; even small changes can have drastic effects.
  • Solar storms (coronal mass ejections) represent a major but underappreciated risk to modern civilization:

    “If the Carrington Event happened now… we would lose hundreds of transformers, and that would cause a massive collapse of the electrical grid… What would happen… could be a global economic collapse.” (36:09–39:31)

  • Historical near-miss: In 1967, a series of solar flares jammed NORAD’s radars, almost leading to a nuclear launch—averted at the last minute.

    "Only at the last minute did solar weather forecaster inform military officers that hey, this is actually a solar flare, not Soviet jamming." (41:45)

2. Venus

[45:03–47:24]

• Earth’s “Twin,” Now Hellish
  • Venus and Earth started similarly but divergent solar/atmospheric history led Venus into a runaway greenhouse state—a stark warning for Earth.
  • Degroot likens Venus to a possible fate for our own planet under unchecked climate change.

3. The Moon

[52:10–58:47]

• Origin: Born from a cataclysmic collision with Theia, profoundly reshaping Earth and possibly enabling life here.
• Selenographers: Early lunar ‘mappers’ searching for signs of change, and thus life, on the Moon.
• Human Contamination:
  • Vast numbers of Earth microbes—e.g., from astronauts’ waste—have almost certainly seeded the lunar surface, some likely still viable.

    "There are microbes that have been detected in the very upper reaches of Earth's atmosphere… Microbes can endure a hell of a lot and so I'm not convinced that there are no microbes on the moon from Earth." (57:52)

4. Mars

[59:07–66:35]

• Persistent Fascination: Mars is both the most Earth-like planet and, potentially, the best candidate for human colonization.
• Canal Controversy: 19th-century “canals” sightings spurred wild speculation about Martians, inspiring a generation of scientists and science fiction, while also discrediting planetary studies for decades.
• Dust Storms and Existential Lessons:
  • Martian storms led to research on planetary cooling mechanisms, ultimately revealing the “nuclear winter” effect—profoundly influencing Cold War politics and the peace movement.

    "…Earth's temperature in the Northern hemisphere would drop by something like 20 degrees Celsius in the immediate aftermath of a nuclear war… and it can all be traced back to the space mission to Mars and the dust storms…" (66:46)

5. Comets and Asteroids

[Quickly discussed, see: 25:15–27:29, 69:28]

• The probability of a catastrophic impact event is low but nonzero—“cosmic dynamite” we poorly understand.

7. Conclusion: Lessons and Calls to Action

[70:07–72:04]

• Space: An Inescapable Environment
  • Humanity cannot “turn away from space”—our survival, well-being, and even history are bound up with cosmic forces.
• Existential Risks & Hope
  • The solar system poses both ancient and newly created existential risks (solar storms, asteroids, nuclear war, AI), but space science can help us prepare.
  • We need better global cooperation and decision-making structures commensurate with these risks.

  • "We are going through this period of heightened existential risk. And we know that in part because of space exploration, space science. So yes, we should fund that a lot more than we are… We also have the ability, we truly have the tested the proven ability to actually reduce those risks and… make our species safer in the cosmos." (71:10)

8. Notable Quotes & Memorable Moments

• On existential risk:

  “It's a disturbing story to my mind… It's very chilling because… the quarantine protocol… was full of potential breaches… People lied to the public about it… That's chilling to me because I think we can see similar conditions now in things like the development of artificial intelligence.” (18:14–21:26)

• On power and democracy:

  “Do we have the ability as a society, as a species, to have a genuine conversation about… how much resources we want to commit to mitigating that risk and… how we want to do it? No, those conversations absolutely are not happening.” (27:29)

• On Earth’s uniqueness:

  "Earth's environments are uniquely valuable in the solar system. And I think that if you can transform the Moon's environment to preserve environments on Earth… then I would support that." (11:04)

9. Timestamps for Key Segments

• 02:28 — Degroot’s motivation and audience
• 05:12 — Environmental history and the “cosmic ocean” metaphor
• 08:49 — Should we alter non-Earth environments?
• 14:37 — Human impacts on Moon, Mars, Venus; contamination risks
• 18:14 — Backward (reverse) contamination and existential risks
• 25:15 — Asteroid and comet threats; who gets a say in cosmic policy
• 27:29 — Failure of democratic decision-making on existential risks
• 33:49 — Book structure: The sun, Venus, Moon, Mars, Comets/Asteroids
• 36:09 — Solar storms and threats to civilization (Carrington Event)
• 41:45 — 1967 Solar flare nearly causes nuclear war
• 45:14 — Why Venus matters for Earth
• 52:10 — The Moon’s origin and significance
• 56:26 — Tardigrades and lunar contamination
• 59:29 — Mars: science and myth; canal controversy
• 66:46 — Martian dust storms, Sagan, and nuclear winter science
• 69:28 — Existential risks from asteroids and comets
• 70:07 — Final lessons and calls to action

Summary: Why This Book (and Conversation) Matters

Degroot convincingly demonstrates that Earth’s fate cannot be separated from solar system forces and that our actions, both intentional and accidental, are reshaping cosmic environments. He urges greater humility, more careful stewardship, and democratic engagement as we enter a new era of planetary and solar system-scale influence—with the stakes nothing less than human survival.

Recommended For:
Listeners interested in history, science, philosophy, planetary science, environmentalism, and the deep, existential questions around humanity’s place in the cosmos.