TWiS 186: Snow on the Moon? - With Dr. Jim Green, Former NASA Chief Scientist

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Nov 14, 2025

Dr. Jim Green, former NASA Chief Scientist and expert in lunar evolution, joins the discussion on the Moon's surprising potential for having snow billions of years ago due to a dense primordial atmosphere. He delves into the interplay between the Earth and Moon's magnetic fields and the implications for early lunar conditions. The chat also covers the importance of NASA's VIPER rover in analyzing polar ices, the fascinating evidence of lunar outgassing, and how ancient lunar weather could have shaped the surface we see today.

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INSIGHT

Moon Formed By Giant Impact

The giant-impact hypothesis explains the Moon forming from debris after a Mars-sized body (Thea) hit proto-Earth.
That newborn Moon started ~4 Earth radii away and receded to today's ~60 radii, lengthening Earth's day over time.

INSIGHT

Moon Stabilized Earth's Climate

The Moon stabilizes Earth's axial tilt, reducing extreme obliquity swings seen on Mars.
This stabilization helped Earth's long-term climate stability and habitability.

INSIGHT

Interconnected Early Magnetospheres

Early lunar rocks show the Moon once hosted a magnetic field and magnetosphere.
That field could interconnect with Earth's, channeling charged atmospheric particles to the lunar surface.

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Snow on the moon? Yes, though not recently... but maybe billions of years ago. Recent discoveries indicate that the early moon, orbiting just 20,000 miles above our planet at the time, may have shared a dynamic magnetic field with that of the Earth, resulting in the moon having an early atmosphere about twice as dense as the Martian atmosphere is today! This has wide implications for planetary science, but perhaps our favorite is that it may have snowed both carbon dioxide and water ice on the moon back in the day. We're also talking about the amazing launch and recovery of New Glenn, the plight of the Chinese taikonauts aboard the Tiangong space station, and a recent SpaceX memo about—no surprises here—a delay to their lunar landing program for Artemis III. Join us!

Headlines:

China's Shenzhou Astronauts Still Dealing with Stricken Spacecraft
Blue Origin's New Glenn Rocket Launches and Lands, Sends Probes Toward Mars
Comet C/2025 K1 Atlas Breaks Up After Solar Flyby
SpaceX Artemis Moon Landing Delayed to 2028

Main Topic: Moon Volatiles and Lunar Science

The Moon's Formation and the Giant Impact Hypothesis
Intertwined Magnetic Fields on the Early Moon and Earth
Transmission of Earth Atmosphere and Volatiles to Lunar Surface
Lunar Outgassing, Volcanism, and Creation of an Ancient Lunar Atmosphere
Permanently Shadowed Regions as Time Capsules of Early Moon and Earth
Scientific Importance of NASA's VIPER Rover for Analyzing Polar Ices and Volatiles
Commercial and Scientific Value of Moon's Minerals and Resources
Long-Term Preservation of Lunar Samples for Future Research
Early Moon Weather: Volatile Snow, Atmosphere Collapse, and What It Means for Lunar Resources
Educational Outreach through Virtual Space Science Experiences

Hosts: Rod Pyle and Tariq Malik

Guest: Dr. Jim Green

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