New study suggests there could be a hidden biosphere six miles below us, under the Earth's crust.

The Hollow Earth hypothesis proposes that the planet Earth either is entirely hollow or otherwise contains a substantial interior space. The scientific community has dismissed the notion since at least the late 18th century. 
Now a new study finds an ecosystem 6 miles beneath the earth crust.
The study, published in The Proceedings of the National Academies of Science, documents the results of a deep-sea drilling expedition at the South Chamorro mud volcano.​
“These organic molecules definitely hint toward life, but the source of that life, as the authors admit, is not clear yet,” Frieder Klein, who studies serpentinization at the Woods Hole Oceanographic Institute tells Geib. Still, he says, the findings are “truly remarkable.”
Could the earth be hollow after all?
Source:http://www.smithsonianmag.com/smart-news/life-could-exist-six-miles-below-earths-surface-180962861/