Decadeslong effort has transformed knowledge of planet’s history

Dominique Mosbergen, WSJ

NEW YORK
EneriesNet.com 02 20 2023

A ship that has spent decades trying to drill nearer to the earth’s mantle is preparing for a new voyage to uncover clues to how life began.

Two dozen geologists, microbiologists and other scientists will sail in April from Portugal aboard the Joides Resolution, a former oil drillship turned research vessel, to the Atlantis Massif, a 14,000-foot underwater mountain rising from the floor of the Atlantic Ocean.

They plan to deepen a 4,640-foot hole drilled nearly 20 years ago to 6,750 feet. The hole won’t be the longest in the seafloor, but it would push closer than ever to the mantle and plumb deeper layers of ocean crust that haven’t been reached before. At the new depth, temperatures are expected to exceed 400 degrees Fahrenheit. 

“It’s going to get hot,” said geologist Peter Blum, the expedition’s project manager. “This is new territory.”

Deepening the hole will be hard. Engineers on the ship plan to lower heavy drilling tools through about 5,400 feet of water to find a hole on the seafloor that is about 15 inches wide. Joides engineers compared the process to standing on a chair and trying to lower a pencil tied to the end of string into the mouth of a soda bottle with a fan blowing.

Adjacent to the mid-Atlantic Ridge, the Atlantis Massif is a tectonic window, where the tectonic plates spread apart and pull the earth’s deeper layers to the surface. By drilling at tectonic windows, scientists can examine parts of the earth’s inner structure that would otherwise be inaccessible.

“It’s almost a way of cheating the system,” said Jason Sylvan, a biological oceanographer at Texas A&M University.

Researchers plan to take samples from the new depths to investigate whether a special mix of rock and water could have spawned life on Earth and possibly other planets. Olivine, a green, magnesium-rich mineral abundant at such depths, is critical to serpentinization, a reaction that occurs when some minerals encounter seawater. Geochemists think serpentinization could help create life. Research suggests the process generates the energy and geochemical conditions favorable to the creation of organic molecules.

“These are the building blocks of life,” said Susan Q. Lang, a geochemist at Woods Hole Oceanographic Institution and the expedition’s co-chief scientist.

The Joides is aiming to drill to a depth where serpentinization is thought to occur but where temperatures are beyond the limits at which life is known to exist. If organic molecules are found there, it could help confirm that serpentinization leads to their creation—and contributed to the genesis of life, Dr. Lang said.

Finding organic molecules in samples from serpentinization sites could also inform the search for life on other planets, she said. The geochemistry of fluids in the plumes of Enceladus, a moon of Saturn, have been inferred by astrobiologists to be similar to the makeup of fluids found at the Atlantis Massif, Dr. Lang said. 

Tectonic windows could also provide a shorter shot at the Mohorovicic discontinuity, or Moho, an elusive boundary deep beneath the earth’s surface. Scientists have been eager to touch the Moho since Andrija Mohorovicic identified it in 1909. The Czech seismologist observed that the velocity of an earthquake’s seismic waves changed when they got to a boundary deep under the earth’s surface. He hypothesized that materials of two different densities met at such spots, causing the wave to change speeds abruptly. 

Scientists first set out to drill through the ocean floor in search of the Moho the same year President John F. Kennedy vowed to send an American to the moon. John Steinbeck chronicled one of their first attempts.  

Many geologists believe the Moho—estimated to be 3 to 6 miles under the seafloor, and much deeper under continents—marks the border between the earth’s crust and mantle. Some scientists also think the Moho could mark sites where rocks have been altered by seawater through processes such as serpentinization.

During expeditions to the Atlantis Massif in 2004 and 2005, scientists said they expected to reach the Moho, which earlier seismic models had suggested was about half a mile under the seafloor there. They drilled—and drilled—but no Moho was plumbed. Subsequent analysis determined the Moho was likely closer to 2.8 miles below the seafloor. 

“You can do remote analysis and make good guesses, but without drilling, you don’t have that ground truth,” said marine geophysicist Donna Blackman, a co-chief scientist on the expeditions. 

Ocean drilling has transformed knowledge of the climate and helped develop models for future warming and sea-level rise, scientists said. It has bolstered the theory of plate tectonics, and allowed microbiologists to find life in the most extreme ocean environments.

The April expedition could be one of the last for the Joides and for the group of about 20 countries that have collaborated on ocean drilling for four decades. The National Science Foundation, which spends about $50 million a year on the ship, most of its costs, said it is evaluating the vessel’s future. 

The multinational collaboration known as the International Ocean Discovery Program is scheduled to end in 2024. Japan and Europe have proposed a new international alliance to replace the program. The National Science Foundation said it would decide whether to join future partnerships based on merit, risk and cost. China has said it is building its own drilling vessel with research capabilities. 

“The scientific community in the U.S. is getting nervous. What is going to happen?” said Antonius Koppers, a marine geologist at Oregon State University. “People have compared the drillship to the Hubble Telescope. For earth scientists, oceanographers and life scientists, it’s been a tremendously unique and important tool.”

Write to Dominique Mosbergen at dominique.mosbergen@wsj.com

wsj.com 02 19 2023