Humanity dwells upon Earth's surface, atop the largest, most diverse layer cake this side of the solar system. Its first layer is a crust as comparatively thin as the skin of an apple. Below that, there's a rocky second layer -- called the mantle -- that's 2,890 kilometers thick and composed of oxygen, silicon, and magnesium, a mixture which flows like seeping asphalt. Deeper still, rests a liquid iron and nickel outer core. Finally, there's a solid, super-dense inner core comprised of the same materials as the outer core.
And in this expansive, unexplored layer cake, one must wonder: is there life? If so, how far down does it go?
These are two questions that still remain unsatisfactorily answered. The distance to the planet's center is, on average, about 6,371 kilometers, and the deepest we've bored is a relatively measly 12.26 kilometers, so we've got a ways yet to explore. In fact, humans have yet to reach Earth's second layer -- the aforementioned mantle.
In 2005, such a venture was planned, but it never got off the ground, or at least into it. Japanese researchers aimed to reach the mantle for the very first time by drilling into the bottom of the ocean.
"One of the main purposes of doing this is finding deep bacteria within the ocean crust and upper mantle," geoscientist Asahiko Taira told The Guardian in 2005.
The rocks in the mantle constitute a unique and fascinating ecosystem. "This is a system which we believe created early life. There may be a chance that we can catch the origin of life still taking place today," Taira said.
What a compelling concept: digging deep into the Earth's foundation to find the foundation for all life on Earth!
In 2010, scientists discovered life in the deepest layer of Earth's crust, the gabbroic layer. A team led by Oregon State University's Stephen Giovannoni drilled 1,391 meters below the Mid-Atlantic ocean floor and found bacterial communities feeding off methane and benzene.
Amazingly, the bacteria appeared to be sustained by organic molecules produced by interactions between water and rock, indicating that these bacteria were thriving in their subsurface environment without any help whatsoever from the sun via photosynthesis! Such a revelation means that life could exist deeper still!
To find out, humankind is preparing to go where no man or woman has gone before: Earth's mantle. A bold, $1 billion dollar mission, organized by the Integrated Ocean Drilling Program, is set to embark. Using the same drilling vessel that was slated to be used in the ill-fated 2005 endeavor, the team plans to drill six kilometers down to the mantle from the bottom of the Pacific Ocean. If sufficient funding is obtained, the expedition could start drilling by the end of the decade.
If and when that project gets underway, who knows what strange intraterrestrial creatures we may find lurking in the deep?
(Image: Rob Lavinsky via iRocks.com)