Story highlights Scientists say they still need to do further research before drilling can begin

But they're hopeful they can begin drilling by 2030

This piece has been updated to reflect that an international team is involved in the drilling attempt.

(CNN) Humans have been to the moon and explored almost every corner of the planet -- but there's one place they have never been.

An international group of scientists say they plan to be the first group to drill successfully into the Earth's mantle, the planet's interior, which lies just beneath the outer crust.

Researchers at Japan's Agency for Marine-Earth Science and Technology told CNN they are hoping to discover more about how our planet was formed and what the mantle is composed of. Japanese media first reported on the project last week.

The mantle makes up more than 80% of the Earth's mass, lying 6 miles (10 kilometers) beneath the ocean floor.

Peridotite is a rock that's believed to make up the Earth's mantle.

"We don't know the exact (composition) of the mantle yet. We have only seen some mantle materials -- the rock is very beautiful, it's kind of a yellowish green," said researcher Natsue Abe, who works for Japan's agency.

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