Humans have been to the Moon and explored almost every corner of the planet -- but there's one place they have never been.
A group of Japanese scientists said they plan to be the first group to successfully drill into the Earth's mantle, the planet's vast molten-rock interior, which lies just beneath the outer crust.
Researchers at Japan's Agency for Marine-Earth Science and Technology (JAMSTEC) say 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 earlier this week.