Planetary Radio: Space Exploration, Astronomy and Science · The Planetary Society

Where did Earth’s water come from? Clues hidden in Apollo Moon dust

·1 hr 2 min·4 clips

Tony says lunar regolith is about one percent impactor material.

Sarah Al-Ahmed frames the episode around a question that sounds simple, but is huge: where did Earth's water come from? She introduces new research that uses Apollo-era lunar samples to trace the history of ancient impacts and place new limits on how much water meteorites could have delivered to Earth. The conversation centers on Tony Gargano, a postdoctoral fellow at the Lunar and Planetary Institute with the University Space Research Association and a research affiliate at NASA Johnson Space Center. Gargano explains how his team used lunar material to build a lunar baseline and construct a mixing array of how much and what type of impactors were brought to the Moon. Oxygen isotopes matter here because they can be measured with very high precision, which lets researchers tease out sub-percent-level additions. The aim is to estimate how much impactor material actually ends up in lunar rocks. That same analysis also helps set new limits on how much water meteorites could have delivered to Earth. Comets come up as a possible source, but the discussion explains why their water would be so isotopically distinct that even a small contribution should show up clearly. Gargano says that case is hard to support once the math and the known differences between comet water and water on Earth are laid out. The episode keeps its attention on the isotope chemistry and what it can and cannot say. A short bonus segment with George Takei shifts the tone a bit. He talks about Star Trek and its influence on generations of scientists and explorers. He also shares why humanity's return to the Moon in the Artemis era means a lot to him. The episode then closes in familiar fashion with Bruce Betts and What's Up. Betts talks about the Allende meteorite, bringing the conversation back to the habit of reading the solar system through physical samples. The episode connects the science and the exploration culture without drifting too far from the question at hand. It keeps the focus on the science and still leaves room for wonder.

As heard by us

Apollo moon dust becomes evidence in a careful case for how Earth may have gotten its water.

This episode turns Apollo moon dust into a clear argument about where Earth’s water may have come from. Sarah Al-Ahmed keeps the discussion steady while Tony Gargano walks through how lunar samples can trace ancient impacts and narrow the case for how much water meteorites might…

Read the full review in PlayNext →

Why you'd press play

You want Apollo dust to help answer one of Earth's biggest questions.

Read the full recommendation in PlayNext →

Listen to the show on

Apple Podcasts Spotify

Play clips from this episode More from Planetary Radio: Space Exploration, Astronomy and Science