The idea: send a drill 2.5 miles to the bottom of the ocean, then use it to drill through another 3.7 miles of crust to penetrate into Earth's mantle, the deepest hole ever dug. The expedition will then be able to study the planet's geological dynamics like never before, and even search for mysterious life that might reside in Earth's underbelly. What could go wrong?

It's all in the spirit of scientific exploration. After all, we've looked billions of light-years into the heavens, but we've still never been capable of peering beneath the crust under our feet.

The expedition is being spearheaded by an international team of researchers led by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), which are in possession of Japan’s massive deep-sea scientific drilling vessel, Chikyu. Currently, the plan is for the team to conduct a preliminary study in the waters off Hawaii in September, to test for its viability as a drilling site, reports Japan News.

It might seem counterintuitive to begin drilling at the bottom of the ocean, but the continental crust is twice as thick as the oceanic crust, so it actually eases the engineering burden significantly to use a drilling ship. If successful, it will be the first time anyone has reached the Earth's mantle, a layer between the crust and the outer core that actually makes up over 80 percent of our planet's volume.

The expedition will give scientists an unprecedented opportunity to study this rocky layer that so fundamentally affects how the planet's tectonic plates drift. The moving mantle also plays a major role in the development of earthquakes and volcanoes, so scientists will have an opportunity to study these processes as well.

Of course, this begs the question: what dangers might come from drilling into a layer of our planet that affects earthquakes and volcanoes? Could we accidentally trigger some kind of catastrophe?

Given that the size of the hole being drilled is so minuscule compared to the volume of the planet, such a catastrophe is highly unlikely. It's not as if penetrating into the mantle is like popping a balloon. For now, researchers are far more concerned with simply overcoming the immense engineering hurdles at play in such an endeavor.

As you might expect, there's also the issue of cost. The price tag for the expedition is estimated to be over $500 million.

“There are still issues to be resolved, particularly the cost,” said Susumu Umino, a professor at Kanazawa University who specializes in petrology. “However, the preliminary study will be a big step forward for this project to enter a new stage."