He Championed Treks to Deep Earth and Inner Space

Illustration: Daniel Hertzberg

“We spend treasures daily on fantastical sky rockets aimed feebly toward space,” wrote John Steinbeck in a 1961 issue of LIFE magazine. “Meanwhile we know practically nothing of far the greater part of our home planet covered by the sea.”

The famous author was embedded on an unconventional offshore drilling vessel, the CUSS I, part of an extraordinary attempt to drill through Earth’s crust. One of the principal minds behind the endeavor — dubbed “Project Mohole” — was Princeton geology professor Harry Hess *32, a chain-smoking, swaggering personality known for thinking outside the box. 

During World War II Hess commanded a Navy ship, the USS Cape Johnson, that used sonar to search for Japanese submarines — readings that he used to map the ocean floor. This process inspired his later research on seafloor spreading that became foundational to plate-tectonics theory. While American aerospace engineers were looking to the stars in competition with Soviet scientists, Hess and other leading oceanographers were contemplating a race to “inner space.”

At a 1957 meeting of the American Miscellaneous Society, an eccentric committee of leading earth scientists who evaluated research proposals over “wine breakfasts,” Hess and oceanographer Walter Munk proposed to drill through the Mohorovičić Discontinuity, the theoretical boundary between Earth’s crust and the mantle beneath, to acquire core samples of the mantle for study. 

With Soviet scientists also pursuing a deep drilling project, the National Science Foundation provided a $15,000 grant to begin Project Mohole. The Americans believed they had discovered a shortcut: Though the “Moho” lies 22 miles below the continental landmasses, underneath the ocean, the crust in some places is only 4 miles thick. Still, those 4 miles of rock lay 2.8 miles below the ocean surface. That made the project extremely challenging — perhaps more difficult than landing a man on the moon. 

While American aerospace engineers were looking to the stars in competition with Soviet scientists, Hess and other leading oceanographers were contemplating a race to “inner space.”

After CUSS I was launched to drill a few hundred meters beneath the oceanic crust, a leading engineering firm, Brown & Root, was hired to pursue the next phase, and budget estimates surged to about $57 million. Discouraged by the rapidly escalating costs, Congress defunded the project in 1966.

While the Mohole was never completed, its attempt led to a series of related NSF ocean-drilling programs that have expanded geological knowledge of Earth’s history. And while the U.S. abandoned the quest, the Soviets kept digging. Their Kola Superdeep Borehole, near Norway, eventually extended 7.6 miles below the surface, the deepest man-made hole dug on Earth. Drilling ceased in 1992 because at that depth, the drill bits were melting under the hellish temperatures.

In a 1966 letter to a colleague, Hess wrote, “The demise of the Mohole Project leaves me unhappy but not so discouraged that I am unwilling to start over again. It is too important a scientific project to be relegated to the next decade.” 

Though he was the champion of the race to inner space, Hess was also involved in the race to the moon. In future lunar missions, he hoped scientists would investigate questions such as whether the moon had once been volcanic and “washed by seas.” He died in 1969, on the day he chaired a National Academy of Sciences meeting celebrating the success of the first moon landing.