2.5 UPDATE – Mantle Rock Recovered
In 1961, GeoTimes magazine published the article Preliminary Mohole Project Drilling Successful. The following are some of the statements that appeared in the article:
The Guadalupe test drilling was concluded on April 12 and the CUSS 1 was towed back to San Diego. Project Mohole, armed with new data and ideas, went back onto the drawing board and into another round of committee meetings devoted to planning the all-out offensive on the Mohorovicic discontinuity. (p. 12)
Despite the spectacular success of the Guadalupe tests a tremendous amount of engineering, planning and development must take place before the supreme effort can be mounted in quest of the Mohorovicic discontinuity. Even if this objective is never ultimately attained, the challenge presented to scientists and engineers in their efforts to reach the mysterious layer of demarcation between the crust and the mantle has resulted already in a major breakthrough in the methods of geologic exploration for that three-quarters of the earth which lies hidden beneath the sea. (p. 13)
Scientists were discouraged that the next phase of drilling for Project Mohole was cost prohibitive, leading Congress to cancel the project in 1966. That same year, Harry Hess wrote in a letter to a colleague:
“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.” (from Blackman, 2021)
Fortunately, scientists have never given up the quest to sample the mantle. With the drilling vessel JOIDES Resolution, it turns out that mantle material was in reach.
Fast-forward to August 8, 2024, when the research journal Science published a paper that no doubt would have Harry Hess and all the AMSOC members feel that all of their efforts were worth it: A long section of serpentinized depleted mantle peridotite. Soon there would be many articles (linked on a News Stories web page), including one in EOS titled Lost City’s Plumbing Exposed by the Longest Mantle Core Ever Drilled. Yes, it finally happened. During IODP Expedition 399 (April-June 2023), scientists brought to the surface a tube of rock more than three quarters of a mile (1268 meter) long containing material from Earth’s mantle.
Image 1: Expedition 399 patch; Image 2: Site map of drilling locations for Expedition 399. (Credit for both images: IODP JRSO, MerlinOne photo archive, CC BY 4.0)
Stay tuned for more exciting results from this expedition for years to come, as we just begin to learn about mantle composition and evolution.
Exercise : Deep Questions About Deep Drilling
On the image slideshow above, you see the Expedition 399 patch, with the official name of the expedition, Building Blocks of Life, Atlantis Massif. Read through the plain language summary of the Preliminary Report of Expedition 399 and respond to the following questions:
a) Why was this expedition called “Building Blocks of Life?”
b) Beyond the historical importance and the impressive engineering it took to recover such a long section of mantle material, why is this discovery scientifically significant? Use information from the EXP 399 Preliminary Report and the EOS article linked above to explain your answer.
c) The Ocean Literacy Principles describe what everyone should know about the ocean — from the surface to the seafloor. But now, scientists have opened a window into what lies beneath the ocean floor. If you were to write one or two new Ocean Literacy Principles about what people should know about the world beneath the seafloor, what would they be? How would you justify adding these new principles?
Tip: You can explore the News Stories about this expedition and its early findings for ideas.
