Tag: caves

Episode 64 Newsletter: Living Underground: Terrestrial and Extraterrestrial

On the day Artemis II launched, the RHR crew headed, with special guest Ernie Bell, PhD, down below the Basement Studio to ask the question fiction keeps digging up, can humans live long-term underground?

In the 64th episode of Rabbit Hole of Research, from the Basement Studio, Joe, Nick, Georgia, and Mary welcome rocket scientist, engineer, and a planetary geophysicist who studied lava tubes and volcanoes, Ernie Bell (currently a Spacecraft Flight Crew Operations Engineer at Blue Origin, and formerly a NASA Extravehicular Activities flight controller and crew trainer) to dig into one of science fiction’s most interesting settings, the underground.

And the timing couldn’t be better. The episode was recorded on the day Artemis II successfully launched, sending a crew of four toward the Moon for the first time since Apollo 17 in 1972. Ernie breaks down what comes next, SLS/Orion, docking with lunar landers from Blue Origin or SpaceX, and eventually, the question of this episode: will our first permanent foothold on the Moon be underground?

The crew explores cave types, karst limestone systems vs. lava tubes, how lava tubes form, why lunar and Martian tubes could dwarf anything on Earth due to lower gravity, and why going underground off-world isn’t just a Handwavium survival trope but a genuine strategy for surviving on other worlds.

They also get into the parts fiction almost always Handwavium away: cave life and extremophiles (Georgia’s favorite word), the silent hazards of CO2 buildup, radon, moisture, and the very real psychological toll of losing your day-night cycle underground, including the wild self-experiment of Michel Siffre. They tackle food (Joe and his calories), water recycling, the lessons of Biosphere 1 and 2, real-world bunkers, and whether Silo, Fallout, and The Expanse actually got any of it right. 

And remember if all else fails, the geothermal heat is free and a bunch of people underground makes for a great rave scene.

Check out what the RHR crew is creating:

Joe:

Future Events to Hang with the Crew:

Podcast Cross-Appearances

Events & Conventions:

It’s Science for Weirdos

Want to support the show? Tell your friends. Follow us on social media, Discord, share the podcast, and let us know what topics you are excited about. Leave a Comment. And for email alerts sign-up for the Substack newsletter and never miss an episode, exciting updates or the bonus images we talk about on the episodes. 

We want to Hear From You (leave a comment):

  • Ernie mentioned that the Moon’s volcanic activity is essentially over, making its lava tubes potentially stable for billions of years. Does that make you more or less interested in living in one (you know Nick will be there)?
  • Michel Siffre spent months underground alone with no clock and completely lost track of time. How long do you think you’d last before you started to unravel?
  • The crew weighed in choosing from Silo, Fallout, The Expanse, For All Mankind, Kong’s Hollow Earth, The Matrix as fictional underground worlds to live in— which fictional underground world would you like to live in (feel free to pick another)?

Drop your thoughts in the comments. We read them all, and your ideas often shape future episodes.

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The RHR in The Basement Studio (Left to Right: Joe, Mary, Nick, Georgia)

Future Episodes

  • Episode 66 – Planetary Defense: Saving Earth from Other Worldly Impact

    Guest: Charles Blue

    Exploring asteroid detection, planetary defense systems, and what it takes to protect Earth from cosmic collisions.
  • Episode 68 – Hive Mind: PlubrisGuest: Wes Thorn (returning guest — Simulation Hypothesis episode)The crew dives into hive minds, collective intelligence, and the blurry line between the individual and the swarm.

Three Part Spider-Man Series to get ready for the new MCU Spider-Man: Brand New Day

  • Episode 70 – Spider-Man Villain Series 1: Lab SafetyGuest: Tera Lavoie, PhDThe science behind Spider-Man’s rogues gallery starts here, with a deep dive into lab safety and what really happens when experiments go wrong.
  • Episode 72 – Spider-Man Villain Series 2: Scorpion and the Other ChimerasGuest: Erin C. AnthonyThe crew explores the science of chimeras, genetic splicing, and what it would actually take to create Spider-Man’s most dangerous foes.
  • Episode 74 – Spider-Man Villain Series 3: What His Villains Reveal About HimGuest: To Be AnnouncedThe conclusion of the Spider-Man trilogy takes a step back to ask what the science of his villains tells us about Spider-Man himself.

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Show Notes & Fun facts 

Movies, TV & Pop Culture Mentioned

  • Michel Siffre’s cave isolation experiments (1962 and 1972)
  • ESA’s CAVES program — astronaut training in cave systems in the Canary Islands
  • NASA’s Controlled Ecological Life Support System (CELSS) research, late 1970s
  • Biosphere 2 (1991–93) — sealed ecosystem experiment in Arizona, still standing and still in use
  • The Greenbrier, West Virginia — Congressional bunker hidden beneath a luxury resort, operational for 30 years
  • Cheyenne Mountain — NORAD’s underground facility, built on 1,300 springs
  • Survival Condo Project, Kansas — decommissioned Atlas missile silo converted into luxury bunker apartments
  • Lava Beds National Monument, Northern California — accessible lava tubes including “Golden Dome,” recommended by Ernie
  • JAXA’s SELENE probe — confirmed a 50km lava tube near the Marius Hills region on the Moon (2017)
  • The Suprachiasmatic Nucleus (SCN) — the brain’s internal clock, disrupted by loss of light cycles underground

Books

  • Journey to the Center of the Earth — Jules Verne (1864) 
  • The Time Machine — H.G. Wells (1895)
  • Caves of Steel — Isaac Asimov (1954) 
  • Wool / Silo — Hugh Howey (2012) 
  • Mars Trilogy: Red Mars, Green Mars, Blue Mars — Kim Stanley Robinson (1993–96) 

Film & TV

  • A Trip to the Moon — Georges Méliès (1902) — early sci-fi classic featuring a cave encounter on the Moon
  • Journey to the Center of the Earth — Brandon Fraser version 
  • Total Recall — Arnold Schwarzenegger (1990) 
  • The Descent (2005) 
  • The Fifth Element (1997)
  • The Matrix — Joe’s dream underground destination
  • Silo — Apple TV+ 
  • Fallout — Amazon Prime — Vault-Tec
  • The Expanse — Ernie’s pick
  • For All Mankind — Apple TV+ 
  • Severance — Apple TV+ 
  • Stranger Things — Netflix 
  • Mars — National Geographic miniseries — Ernie’s recommendation
  • Snowpiercer
  • Ice Age
  • Kong: Skull Island / Godzilla vs. Kong — Nick’s underground destination of choice
  • Squid Game

Video Games

  • Fallout series (1997–)

Fun Facts to Impress Your Friends With:

  1. Lava tubes on the Moon could be enormous. Due to the Moon’s lower gravity, lunar lava tubes are estimated to reach 300–400 meters across — large enough to fit a city inside. On Earth, the biggest tubes Ernie has been in are around 20 meters in diameter. The Moon’s volcanic activity is essentially over, meaning those tubes have been sitting stable for billions of years.
  2. The olm salamander is the ultimate cave survivor. This blind, pale cave-dwelling amphibian can live over 100 years and go up to 10 years without food. It has no eyes, no pigmentation, and has adapted so completely to cave life that it cannot survive outside of it. Real cave evolution makes fictional cave monsters look very unambitious.
  3. Michel Siffre lost his mind underground — literally. In 1962 the French speleologist spent two months alone in a cave with no clock. His internal day stretched from 24 hours to 48 hours. By the end he thought only 34 days had passed. When he repeated the experiment for six months in 1972 he psychologically unraveled around month four — crying without cause, unable to concentrate, and near suicidal. Fiction almost never shows this.
  4. Feeding an underground colony is harder than fiction makes it look. NASA’s Controlled Ecological Life Support System (CELSS) research from the late 1970s determined that a crew of four needs approximately 50 square meters of agricultural growing space per person to be nutritionally self-sufficient. Most fictional underground cities show one small room of plants feeding hundreds of people. That’s pure Handwavium.
  5. There is more life underground than above it. Estimates suggest 15–23 billion tonnes of carbon exist as microbial life underground — more biomass than all surface plants and animals combined. Extremophile bacteria have been found 3km underground in South African gold mines, living off hydrogen produced by radioactive rock decay with no sunlight and no photosynthesis whatsoever. Life, uh, finds a way.

Episode Highlights

  • 00:00 Basement Studio Roll Call — Joe, Nick, Georgia, and Mary welcome rocket scientist and engineer Ernie Bell to the Basement Studio.
  • 00:22 Meet Ernie the Rocket Scientist — Ernie casually introduces himself as a rocket scientist working on lunar landers, formerly a planetary geophysicist who studied lava tubes — “rockets and stuff.”
  • 01:22 Artemis Launch Excitement — The crew celebrates the successful Artemis II launch, the first crewed mission to the Moon since Apollo 17 in 1972, recorded on the day it happened.
  • 03:41 Moon Bases and Going Underground — Ernie explains that moon bases will start on the surface, but papers going back to the 1960s and 70s have made the case for eventually going underground.
  • 05:15 Why Humans Fear Below — Joe delivers the cold open: every culture has a word for what’s below, our ancestors painted in caves with no natural light, and fiction has been obsessed with the underground ever since.
  • 07:01 What Makes a Cave — Ernie breaks down the two primary cave types on Earth: karst limestone formations and lava tubes, and how each forms differently.
  • 07:31 How Lava Tubes Form — Ernie walks through the inflation and drainage process that creates lava tubes, including the cooling skin, structural integrity, and how the molten lava drains out leaving a void.
  • 08:59 Skylights and Tube Reuse — The crew learns about skylights — holes in lava tube ceilings from collapse or formation — and that tubes can be reused by subsequent lava flows, leaving behind benches and “lava-sickles.”
  • 11:55 Lava Tubes on Moon and Mars — Due to lower gravity, lunar lava tubes could be 300–400 meters across. Ernie describes a known pit at Marius Hills with a ceiling 25 meters thick and 40 meters of void space beneath it.
  • 15:40 Cave Life and Extremophiles — Joe and Ernie discuss troglobites, the deep biosphere, and the golden microbial growth Ernie has seen firsthand at Lava Beds National Monument in Northern California.
  • 17:57 Health Risks Underground — The crew covers CO2 buildup, moisture, radon, vitamin D deprivation, and Ernie’s personal story of getting turned around in a limestone cave as a kid.
  • 19:57 Circadian Rhythm Breakdown — Joe details Michel Siffre’s cave isolation experiments, his internal clock drifting to 48 hours, and his psychological unraveling in month four of his 1972 experiment. Ernie notes astronauts on the ISS experience 16 sunrises a day and have to maintain their day-night cycle by the watch.
  • 24:32 Sci-Fi Underground Realism — The crew debates how well Fallout, Silo, and The Expanse handle the realities of underground living, with Ernie praising The Expanse for thinking seriously about agricultural scale and agoraphobia in returning Martians.
  • 28:35 Biosphere Experiments and Vaults — Joe and Ernie break down Biosphere 2 — oxygen crashes, faction formation, failed food production — and how it mirrors Vault failures in Fallout.
  • 31:27 Bunkers, Catacombs and Getting Lost — The crew covers the Greenbrier, Cheyenne Mountain, luxury missile silo condos, the Paris Catacombs, and Ernie’s childhood experience of getting lost in a limestone cave.
  • 36:27 Cave Anxiety and Total Darkness — Joe brings up infrasound at 18–19Hz resonating in cave passages causing anxiety, unease, and a sensation of presence. Ernie confirms that even in big lava tubes, true darkness sets in very quickly.
  • 37:52 Underground Protection Basics — Ernie explains the three key protections caves provide off-world: radiation shielding, thermal regulation, and micrometeoroid protection, and how even covering a surface habitat with regolith provides some of those benefits.
  • 39:23 Sealing Caves and Quake Risks — The crew discusses sealing cave systems to hold atmosphere, moonquakes and marsquakes, and how you’d engineer around structural risks the same way Californians build for earthquakes.
  • 40:08 Building Habitats Inside Tubes — Ernie describes the concept of placing inflatable or rigid habitat structures inside a lava tube so that even if the cave shakes, you don’t lose your atmosphere.
  • 42:02 Food and Water Reality Check — Joe drops the NASA CELSS figure: a crew of four needs 50 square meters of agricultural space per person to be self-sufficient. Ernie explains that lunar water ice is likely distributed in regolith like damp sand, not in glaciers, making extraction a serious engineering challenge.
  • 47:33 Growing Underground and Biohacks — The crew discusses hydroponics, genetic editing, algae, and cyanobacteria as potential food and CO2 scrubbing solutions for underground colonies.
  • 51:36 Yeast Diet and Space Snacks — Joe references Asimov’s Caves of Steelyeast vats as the likely underground diet. Ernie sets the record straight on what astronauts actually eat — rehydrated meals, M&Ms by another name, and no, the freeze-dried ice cream is just for tourists.
  • 53:30 How Astronauts Train — Ernie describes astronaut training in vehicle mockups, running through timelines and activities exactly as they will in space, including food testing. He then jokes that they actually just put them on a rocket and say good luck.
  • 56:04 Lava Tubes and Science Value — Ernie points out that beyond practical habitation, lava tubes give access to geology that is tens to hundreds of millions — potentially billions — of years old, with no surface weathering.
  • 57:17 Life in Martian Caves — Joe asks whether Martian caves are the most likely place to find remnants of life. Ernie notes the Moon is unlikely, Mars is possible, and the more benign thermal environment of a cave would be an advantage.
  • 01:00:43 Would You Move to Mars — Ernie says yes, he’d go — exploration is part of what humans need to keep moving forward. Mary is a hard no. Joe would go to study the life. Nick is packed and ready. Georgia wants a postcard.
  • 01:06:34 Cost to Reach Space — Ernie estimates launch costs have dropped dramatically with SpaceX’s Falcon Nine, from roughly $10,000 per pound down by nearly an order of magnitude, though the SLS that launched Artemis II costs on the order of a couple billion dollars per rocket.
  • 01:08:13 Favorite Fictional Undergrounds — Ernie is torn between For All Mankind and The Expanse, and recommends Kim Stanley Robinson’s Mars Trilogy. Joe wants the Matrix rave. Mary wants to be part of the mycelium network. Georgia and Nick are headed to the Hollow Earth in the Kong-verse.
  • 01:12:13 Wrap Up and Next Topics — The crew thanks Ernie, celebrates the Artemis II launch, and teases the next episode on planetary protection — what happens when we start dropping things on other worlds?

“Stay curious, stay safe… Love Y’all!”

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