Katherine de Kleer: Professor of planetary science and astronomy at Caltech who studies the surfaces, atmospheres, and thermochemical histories of planets and moons. She uses telescopes to observe volcanoes on Io, atmospheres on Titan, and other solar system objects.
What this episode covers
Lex Fridman talks with Caltech planetary scientist Katherine de Kleer about why Pluto was demoted, and why she considers moons the next frontier of exploration. She makes the case for Io as the most volcanically active body in the solar system and explains how tidal heating could make the subsurface oceans of Europa and Enceladus habitable. The conversation ranges across Titan's prebiotic atmospheric chemistry, the disputed phosphine detection on Venus, asteroid impact risk, and the interstellar object Oumuamua. They also explore the limits of scientific skepticism, the importance of curiosity over authority, and end on her favorite difficult books and a Robert Frost poem.
Recommended on this episode
Pale Fire
Vladimir Nabokov
“one of the first books that really captured my fascination was nabakov's book pale fire”— Katherine de Kleer
The Duino Elegies
Rainer Maria Rilke
“he wrote this series of poems called the duino elegies that were very impactful for me personally just emotionally”— Katherine de Kleer
The Dream Life of Sukhanov
Olga Grushin
“she wrote this just phenomenal book called the dream life of sukhinov that i read this year maybe it was last year”— Katherine de Kleer
The Remains of the Day / Kazuo Ishiguro novels
Kazuo Ishiguro
“kazuo ishiguro who's pretty much all of his books are like slow reveals over the course of the book”— Katherine de Kleer
Also referenced (named, not recommended)
Terminator 2: Judgment Day
James Cameron
“it's like terminator 2 when it's like the thing that's just like you shoot it and splashes and then comes back together”— Katherine de Kleer
The Hitchhiker's Guide to the Galaxy
Douglas Adams
“like uh hitchhiker's guide to the galaxy like if you had to report like write a paper on earth”— Lex Fridman
Big reveals from this episode
- de Kleer admits she personally doesn't care how objects are classified, and often calls her favorite moons 'planets' because they have volcanoes, geology, and atmospheres.
- She explains that tidal heating from orbital resonance could be driving hydrothermal activity at the base of Europa's ocean, a promising condition for life.
- de Kleer says she does not personally believe phosphine was even detected on Venus, pushing back on the famous 'life on Venus' claim.
- On Oumuamua, she says that as a scientist she cannot rule out alien space junk, but invokes Sagan's 'extraordinary claims require extraordinary evidence.'
- She argues the scientific method is so good at finding alternate explanations that it can crush genuinely interesting outlier evidence.
- Career advice reveal: the techniques you use matter as much as the questions you study for happiness in a scientific career.
- Asked to choose fire or ice for the end of the world, she picks fire because slow cold death feels far more depressing than explosive activity.
Worth remembering
- Io is the most volcanically active object in the solar system, with hundreds of active volcanoes and plumes reaching hundreds of kilometers high.
- Tidal heating from orbital resonance flexes Io's shape by a couple hundred meters per orbit, enough friction to melt its mantle rock.
- Io's volcanoes are the source of charged particles that populate Jupiter's entire magnetosphere, making Io a massive polluter of the Jupiter system.
- Titan has an atmosphere denser than Earth's and does prebiotic chemistry, forming complex organic molecules while staying freezing cold.
- Plate tectonics makes Earth unique in the solar system, and aliens could infer it just by mapping where volcanoes line up.
- Storm clouds on giant planets are condensed molecules like ammonia ice or methane ice, and different species produce different colors.
- Uranus orbits on its side with a 42-year orbital period, so its poles get roughly a decade of direct sunlight at a time.
- The asteroid Apophis will pass closer to Earth in 2029 than some geosynchronous communication satellites, but will not hit.
- Oumuamua's odd long, thin shape may come from ice sublimating off its surface, weathering it like a worn-down bar of soap.
- On Mars, farming insects like cockroaches may be the easiest way to produce protein for a self-sustaining colony.