Project Mohole
Today, Inner Space versus Outer Space. The University of Houston presents this series about the machines that make our civilization run, and the people whose ingenuity created them.
______________________
We saw two human reaches in 1957 – one off Earth’s surface, and one into Earth’s surface. That year, Russia launched Sputnik – the first man-made satellite to orbit Earth. And we initiated a plan to penetrate into Earth’s surface. How did that work?
Imagine we were to dig down – from as little as three miles below the ocean floor, or to as much as dozens of miles down into dry land. We would reach a discontinuity between Earth’s crust and its mantle. We call that dividing line Moho – short for the Mohorovičić discontinuity. Below it lie thousands of miles of a dense rock mantle – all the way down to our molten core.
But: So much we do not know about the nature of that mantle below the Moho boundary. So a group formed. They got our National Science Foundation to fund five million dollars for a project to drill down into it. They named the project Mohole and set to work – drilling off the coast of Mexico. And from there the fun begins:
Cuss I, the first Moho drill ship (Image Courtesy of Wikimedia Commons)
It all began with great fanfare. Test drilling started after three years of preparation. Five holes. And one got down all the way to six hundred feet – a pale fraction of what was needed. But it seemed this was going to work! Time Magazine arranged for Americas’ famous writer, John Steinbeck to join the project as its chronicler.
John Steinbeck (Image courtesy of Wikimedia Commons)
Of course, the project was harder than it first seemed. Pretty soon they needed 125 million dollars to finish it. It stumbled along, making a few useful discoveries about Earth’s crust. But it failed to get any deeper than six hundred feet – while it needed to go somewhere between three to six miles.
Steinbeck grew restive. He’d originally said that the boat was like an outhouse sitting upon a garbage scow. And his assessment did not improve. The project finally had to quit. Much criticism of government science funding followed. And yet – and yet, they had accomplished something:
They’d managed to drill past the portion of Earth’s crust that was all sediment. They’d finally reached basalt – the hard rock that makes up most of the crust. But they fell far, far short of reaching Earth’s mantle.
Failure is, after all, our greatest teacher. We’d actually begun a quest that would continue. Finally, in 2023, an ocean-drilling vessel drilled deep enough to extract a sample of what might be rocks from Earth’s Mantle. Well, they also might’ve been contaminated by seawater. But no matter. For now we have, at least a true harbinger of success.
And Mohole? Well, it turns out to’ve been the first flicker of our seeing beyond what lies without – to seeing what lies within, as well.
I’m John Lienhard, at the University of Houston, where we’re interested in the way inventive minds work.
(Theme music)
Some online sources:
Mohorovičić discontinuity - Wikipedia
Lisa Margonelli, Mohole Moments: Issues in Science and Technology, pp 16-18, National Academy of Sciences. Spring 2026. This is also available here: Mohole Moments | Editor’s Journal
This Episode first aired on July 20, 2026.