Underwater 1.2km-deep hole in Earth's mantle can hold clues to origins of life

The deepest hole to have ever been drilled into Earth's mantle has just been dug in the middle of the North Atlantic Ocean. Scientists dug 1,268 metres below the seafloor near an underwater mountain called Atlantis Massif. The initial plan was to just go 200 metres deep, which also was ambitious considering this had never happened before.

The drilling has exposed a new rock core which can offer insights into how life began on Earth, besides about the evolution of the planet's outermost layers. Earth is composed of different layers - a solid outer crust, an upper and lower mantle and a core. The upper mantle is responsible for earthquakes, and other processes like the water cycle and the formation of volcanoes and mountains. However, scientists have not had much access to the mantle.

However, Atlantis Massif which sits deep within the sea is a region where the mantle is exposed.

“To date, we’ve only had access to fragments of the mantle,” Johan Lissenberg at Cardiff University says. “But there are a number of places where the mantle is exposed on the seafloor.”

This mountain became the candidate to explore the mantle and dig into the fascinating history of Earth. Atlantis Massif is situated near a volcanically active region of the mid-Atlantic ridge. Volcanoes here are a result of parts of the mantle continuously surfacing and melting. The mantle is also the reason for microbial life thriving.

When seawater seeps deeper into the mantle, chemical compounds such as methane are produced due to the hotter temperatures. These compounds move upwards through hydrothermal vents and act as fuel for microbial life.

Why dig a hole underwater?

Some experts believe that life on Earth began in the depths of the ocean near hydrothermal vents. So microbiologists think that studying these regions can help learn about the conditions that triggered life.

So, using a drilling ship JOIDES Resolution, Lissenberg and his team started drilling with plans of going 200 metres into the mantle. “We recovered really long sections of continuous rocks and decided to stick with it and go as deep as we could," Andrew McCaig from the University of Leeds, who was part of the team, said.

They managed to reach a whopping depth of 1,268 metres into the mantle and found signs of significant melting in this part of the mantle. Reconstructing the melting process in the future can help us understand how molten rock feeds oceanic volcanoes.