EarthDate is a short-format weekly audio program delivering concise, science-based stories about the Earth: its geology, environments, and the processes that shape our planet over deep time and today. Beginning in 2026, EarthDate is managed by Switch Energy Alliance and hosted by SEA's founder Dr. Scott W. Tinker. Together, we explore earth systems, natural resources, and their relevance to everyday life, with a focus on clear, accessible science education for broad audiences. EarthDate is written and directed by Emmy-winning filmmaker Harry Lynch, and researched by Lynn Kistler. We search for captivating stories to remind listeners that science can enlighten, educate and entertain.
Rust is common on Earth. It shouldn’t exist on the moon. But somehow, it does.
Rust is just the common name for iron oxide. Iron that has bonded to oxygen.
The moon, however, has no oxygen. Yet lunar rovers have recovered grains of iron oxide in lunar soil. How could they have gotten there?
One possibility is from Earth. Or rather, from our atmosphere.
The magnetic field of our planet, called its magnetosphere, surrounds Earth like an invisible force field.
The sun produces a solar wind of charged particles that flows outward into the solar system.
When it encounters our magnetosphere, it deflects around Earth. The charged particles flow around us and deep into space, in a so-called magnetotail that stretches three million miles behind Earth.
As the charged particles pass, they strip off some oxygen ions from the upper reaches of our atmosphere, and carry them into the long magnetotail.
Each month during the full moon, Earth is between the moon and the Sun, which may shelter the moon from solar wind, and bathe it in oxygen from Earth’s magnetotail.
Scientists believe that when these oxygen ions strike the moon’s surface, they bond with iron in the lunar soil to form, yes, tiny particles of rust.
This is still a hypothesis. But it’s important because it highlights how little we know about our closest celestial neighbor… where humans might soon spend a bit more time.
22 Sept 2026
Sole Survivors
Imagine there was not one species of human…but many. One stronger. One smaller. All different, but closely related.
Around 40,000 years ago, that’s exactly how it was. Homo sapiens – us – shared Earth with several other Homo species. Then those other ones went extinct, and we carried on. The sole survivors.
Why? Because we could better adapt to changing climates. And that’s because of a few key qualities.
First, we had more flexible diets. We could eat large animals or small. Fish, fowl, or foraged plants.
One reason we could do that, is we also had better control of fire. Which allowed us to cook those various foods to extract more nutrients and calories.
We also had better tools, to more effectively butcher animals, and importantly, sew their hides into fitted clothing and covering for shelters -- which allowed us to endure the bitter cold of the Ice Age.
And because of those things, we were mobile. We could take our tools, clothing and shelters, flexible diets and fire to cook them, to different regions as climate patterns changed.
We also had dogs, for hunting. And to hear that amazing story, look it up on EarthDate.org.
But there’s one more Homo sapiens trait that may have mattered most of all. We had advanced language, to communicate the knowledge of all these things, to cooperate and collaborate, and to build the social cohesion required to weather difficult environments.
15 Sept 2026
Gold is Abundant
Gold is rare. Except in one place on Earth that it’s incredibly plentiful. But we’ll probably never get to it.
Over the course of human civilization, people have searched for gold. Still, we haven’t found much – 220,000 tons across all those centuries. By comparison, we’ve mined seven times as much silver. And 3,000 times more copper.
But we now know there’s much, much more gold on Earth.
When the planet formed, more than 4 billion years ago, many metals swirled together in Earth’s molten magma, gold among them. Being heavy, it was pulled toward the center, into Earth’s core, by the force of gravity. There it bonded with abundant iron. And there it has mostly stayed.
But Earth’s interior is not static. The molten magma sometimes upwells toward the surface.
Over millions of years these magma currents have carried small amounts of gold and other metals out of the core.
Earthquakes and shifting tectonic plates then brought that magma toward the surface. Some of it precipitated out in veins, which we have mined. And some of that eroded into rivers and streams, and we gathered it there too.
Because it’s valued, and doesn’t oxidize, most of the gold we’ve found over the years still exists in pure form and gold-rich alloys, and is still in use – in jewelry, art, electronics, even medicine.
It may be precious, but it’s not scarce. It’s just that Earth has limited our access.
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