Beyond the abyss: The mission to drill through the Earth’s crust

CNN  — 

Last month, floating in the ocean south of New Zealand, a team of scientists were investigating the end of the dinosaurs and trying to predict the future.

They were unspooling Earth’s history, raising up sections of sediment and ancient rock from beneath the South Pacific. With these samples, scientists are probing some of our most longstanding, and most urgent, questions: What happened in the wake of the dinosaurs? What happens to life when the planet dramatically warms or cools? Can millions of years of Earth history tell us where we’re heading?

The abyss may hold the answers.

“The workings of the oceans, the Earth’s environment and climate are all recorded in the sediments,” explained Anthony Koppers, a professor of marine geology at Oregon State University.

Drill beneath the sediment on the sea floor and you hit the oceanic crust. One advantage of drilling into oceanic crust is it’s approximately 7 kilometers thick, while on land it is many times thicker, explained Koppers. That allows scientists to sample closer to the Earth’s mantle.

“You’re learning about how the world works at a planetary scale,” he added. “There’s a fundamental question about the origin of life on Earth, and then (by) extension, to any other planet.”

An unidentified machine being used for the Mohole Project Expedition Ship. The expedition took place in 1961 and paved the way for future scientific drilling operations at sea.

Scientific ocean drilling took off in the late 1950s and early ’60s with Project Mohole, a US attempt to drill to the base of the crust. It didn’t get close – drilling 601 feet (183 meters) – and to date the deepest a scientific vessel has drilled beneath the seafloor is 3,250 meters, by Japanese ship Chikyu in 2019.

The moonshot of drilling through to the upper mantle remains a way off, but Koppers cautioned against fixating on the numbers game: “drilling a deep hole – it’s not that interesting. It’s what we can answer with that.”

Ocean drilling has provided evidence of the theory of plate tectonics (the movement of the plates comprising Earth’s rocky outer layer); revealed the Arctic once had a subtropical climate; discovered frozen methane hydrate, a flammable ice; found microbial life deep beneath the sea floor.

“We have only been chipping away at the very, very top surface,” he said. “Over 50 years, we’ve gradually got a little bit more insight, and actually it has caused way more questions than answers.”

Now Koppers and the scientific ocean drilling community is laying the groundwork for a literal breakthrough.

“Something every paleoceanographer dreams of”

Cut cores undergoing examination during the recent IODP Expedition 378.

For decades, the JOIDES Resolution, a 41-year-old ex-oil drilling ship, has served as the community’s primary vessel for deep ocean drilling.

Conducting research for the International Ocean Discovery Program (IODP), the Resolution’s last mission had it floating above the Campbell Plateau south of New Zealand. Among the crew of 118 were Laura Haynes, a sedimentologist and post-doctoral fellow at Rutgers University, and Elizabeth Sibert, a physical properties specialist and junior fellow at Harvard.

“Sailing on the JOIDES is something that every paleoceanographer dreams of,” said Haynes. “I’ve been waiting for an opportunity … for almost 10 years,” Sibert added.

Working seven days a week rotating 12-hour shifts for 60 days, it was no cruise for the 30 scientists at sea. “There are no breaks, there are no port calls, there’s no alcohol on board,” said Brad Clement, director of science services at the IODP.

Drilling takes place all hours, with 9.5 meter long core samples hauled to the surface for immediate analysis. Cores are then split lengthways and stored in a refrigerator for use in further research.

Microfossils examined by Laura Haynes aboard the JOIDES Resolution. The rainbow colored microfossil on the left and the carbonate microfossil on the right (stained blue) are fractions of a millimeter wide.

Koppers says the ship can penetrate through around seven kilometers of sediment in a two-month period, although “you’re lucky (to) get a kilometer” through the harder crust.

The team drilled down far enough to see evidence of the Paleocene-Eocene Thermal Maximum, a global heating event that occurred approximately 55.5 million years ago and, said Haynes, “our best analog to anthropogenic climate change.” Part of the expedition’s mission, said Sibert, was “to understand how life responds to major global change, such as rapid global warming or cooling, and mass extinction.”

Sibert has already been involved in a study on a mass extinction event – that of the dinosaurs – published early 2020 using cores extracted in 2012. It found compelling evidence to support the theory that the dinosaurs were wiped out after an asteroid impacted near the Yucatan, in Mexico.

Long term plans

Elsewhere, knowledge gaps abound. For example, how carbon dioxide interacts with the subseafloor and mantle, said Koppers. Understanding that could help determine what role the oceanic crust could play in future carbon sequestering.

Among the initiatives planned by the IODP for the next three decades is probing the deep Earth – the moonshot of hitting the upper mantle being one goal. Koppers estimated it would take “a year, if not more” to drill through 7 kilometers of crust. Multiple sites, including one close to Hawaii, are being discussed.

“The challenges when you get to those depths (are) the temperatures are very high and the pressures are very high. So, every time you try to pull the pipe out to change the bit, the hole seals itself back up,” Clement explained. “It might take 10 to 20 years to get the technology.”

The JOIDES Resolution leaving Hawaii in 2009. Named after Captain James Cook's ship the HMS Resolution, she has travelled to all corners of the world, and as a result doesn't have a home port.

But all of that is still to come. Meanwhile, the Resolution is heading to port loaded with over 900 meters of core. Immediate finds by the crew will give way to the slow churn of peer-reviewed research.

Sibert said the team is excited to delve into evidence of the start of the Cenozoic Era, 66 million years ago, after the “reset button” of the dinosaurs’ mass extinction, as well as the Eocene-Oligocene Boundary, “when ice sheets became a permanent feature on Antarctica.”

“(We’ve) found a number of things we weren’t expecting,” said Sibert. “With ocean drilling, you never really know what you’re going to get until it comes up on board.”