Or there will be, next year. Japanese researchers plan to drill a hole more than four miles through the Earth's rocky crust to reach the molten mantle below. This will be quite a feat — the deepest hole to date is less than a mile-and-a-half. And, just to make things interesting, they're going to do it from a boat floating a mile and a half above the sea floor. (That's where the Earth's crust is the thinnest.)
The project has several goals. They hope to learn more about undersea earthquakes, like the one that caused the Indian Ocean tsunami. They will also study the rocks and mud for records of climate change. And they will look for microbes and other signs of life in this extreme environment.