Mission to the Mantle

Earth’s crust is broken into slabs of rock called tectonic plates. Underneath is the mantle, a layer of rock 2,900 kilometers (1,800 miles) thick (see Layers of Earth). Most of it is solid, but parts are hot enough to flow like liquid. 

Tectonic plates glide over the mantle at about the speed fingernails grow. When the edges of plates push against each other, earthquakes and volcanic eruptions can result.

Pulling up a piece of the mantle would help scientists earn how Earth formed. Last year, MacLeod and other scientists found a perfect spot to try. The site is on a rocky hill at the bottom of the Indian Ocean. Here, Earth’s crust is thin—only 5 kilometers (3 miles) deep. The team set out on a ship designed for serious drilling.

Earth’s crust is broken into slabs of rock. They’re called tectonic plates. Below is the mantle. This rock layer is 2,900 kilometers (1,800 miles) thick (see Layers of Earth). It’s mostly solid. But parts are hot and flow like liquid. 

Tectonic plates glide over the mantle. They move at the speed fingernails grow. The edges of plates can push against each other. That causes earthquakes and volcanic eruptions.

Scientists want to see a piece of the mantle. It could help them learn how Earth formed. MacLeod and other scientists recently found a perfect spot to dig. It’s at the bottom of the Indian Ocean. Earth’s crust is thin there. It’s only 5 kilometers (3 miles) thick. The team set out on a ship made for drilling.

During December and January, the team drilled down 789 meters (2,589 feet). They plan to return to the site several times over the next few years to drill all the way to the mantle (see Deep-Sea Drilling).

The mission is already starting to answer exciting questions. One big one: How far below the crust can life survive?

Scientists used to think living things could thrive only in mild conditions. But then they began discovering tiny microbes in unlikely spots, from boiling springs to frozen lakes. “Now we find life everywhere we look,” says Ginny Edgcomb, a biologist at WHOI.

The team drilled down 789 meters (2,589 feet) in December and January. They plan to return to the site several times. They’ll drill further and further over the next few years. Eventually, they hope to reach the mantle (see Deep-Sea Drilling).

The team is already starting to answer big questions. For example, how far below the crust can life survive?

Scientists used to think life exists only in mild conditions. But then scientists began finding tiny microbes in odd spots. Some of these spots included boiling springs and frozen lakes. “Now we find life everywhere we look,” says Ginny Edgcomb. She’s a biologist at WHOI.

As the scientists have drilled, Edgcomb’s team has pulled up rock samples to check for microbes. So far, they’ve found living things as far down as they’ve taken samples. 

Edgcomb can’t wait to see what might live even closer to the mantle. Deep inside Earth, conditions may have barely changed since the planet formed. “If we find something there,” she says, “it could give us clues about the earliest creatures that lived on Earth.”

Edgcomb’s team pulled up rock samples as they drilled. They checked the samples for microbes. So far, they’ve found living things as deep as they’ve drilled. 

Edgcomb can’t wait to see what might live even closer to the mantle. Conditions deep inside Earth may have changed little since the planet formed. “If we find something there,” she says, “it could give us clues about the earliest creatures that lived on Earth.”