Carbon-rich worlds contrast sharply with the Earth, whose interior is relatively poor in that element but rich in oxygen.

BBC: Oddballs: The strange worlds beyond our Solar System

Those created in the atmosphere on the other side of the world, which then had to make the 20, 000km (12, 000 mile) journey through the earth's interior to get to Japan, would have had a chance to turn their coats.

ECONOMIST: Neutrinos

Here's one example why we should care: in 1977, diving in the human occupied vehicle Alvin, scientists investigating a volcanic ridge 2500 m (1.5 miles) below sea-level found something totally unexpected -- lush ecosystems thriving at hydrothermal vents fueled by chemical energy released from the Earth's interior.

CNN: Probing the ocean's undiscovered depths

Given all the discoveries that we have made from an up-close investigation of these ocean ridges, we can't help but wonder what we might find at the far end of the same plate tectonic cycle where seafloor is drawn back into the Earth's interior at deep-ocean trenches.

CNN: Probing the ocean's undiscovered depths

According to tectonic theory, the surface of the Earth is made up of a patchwork of massive rigid plates, about 80km (50 miles) thick, which float in slow motion on top of the Earth's hot, pliable interior.

BBC: The Pacific 'Ring of Fire'

Plate tectonics, the formation of faults and the moving of the continental crust over a molten interior, is a characteristic unique to Earth and it meant that minerals evolved far beyond those on any other planet in the Solar System.

ECONOMIST: Minerals

The interior of Mars holds vast reservoirs of water, with some spots apparently as wet as Earth's innards, scientists say.

MSN: Scientists say parts of Mars interior are as wet as Earth's