Despite the fact that it likely contains water and a rocky core, that water is almost certainly in the form of steam or a supercritical fluid.

FORBES: NASA Detects The Light Of A 'Super-Earth'

That depth provides enough pressure to turn CO2 into what is known as a supercritical fluid, a form in which the stuff is more likely to stay put.

ECONOMIST: A survey of The future of energy: Dig deep | The