Drilling to the Center of the Earth 298
indylaw writes "Japanese scientists are attempting to explore the centre of the Earth." From the article: "Using a giant drill ship launched next month, the researchers aim to be the first to punch a hole through the rocky crust that covers our planet and to reach the mantle below. The team wants to retrieve samples from the mantle, six miles down, to learn more about what triggers undersea earthquakes, such as the one off Sumatra that caused the Boxing Day tsunami."
Wrong bloody title. (Score:5, Informative)
From "A short history of nearly Everything" (Score:2, Informative)
About the earth's layers (p216): "... the various layers, using average figures:
From 0 to 40 km (25 mi) is the crust.
From 40 to 400 (250 mi) is the upper mantle.
From 400 to 650 (400 mi) is a transition zone between the upper and lower mantle.
From 650 to 2,700 km (1,700 mi) is the lower mantle.
From 2,700 to 2,890 (1,900 mi) is the "D" layer.
From 2,890 to 5,150 km (3,200 mi) is the outer core,
and from 5,150 to 6,378 km (3,967 mi) is the inner core."
About an attempt to drill the "Mohole" during the 60's (p214)
"Drilling from a ship in open waters is, in the words of one oceanographer, 'like trying to drill a hole in the sidewalks of New York from atop the Empire State Building using a strand of spaghetti.'"
A very cool book.
Similar projects (Score:5, Informative)
There have been a number of other projects to drill deep into the Earth's crust, though none has succeeded in reaching the mantle, as this Japanese team is trying to do. Some of the more well-known ones:
Another poster already provided the wikipedia page for Project Mohole [wikipedia.org]. That was a US team back in 1961 that managed to drill to 183 m below the sea floor, in 3500 m of water off the Mexican coast. From a ship, floating on the ocean surface -- I just find that incredible.
As far as land-based projects go, there have been 2 big ones that I know of. The Kola Superdeep Borehole [wikipedia.org] was a Russian project, started in 1970, that drilled at a site on the Kola Peninsula near Finland. Their deepest hole reached 12.262 km in depth, which is the current record. This page [compuserve.com] has a section (scroll down a few screens) with some very interesting findings from the project. Apparently, geologic theory doesn't quite correspond with what we find when we actually go down there to see for ourselves.
There's also the KTB (long German acronym) Borehole, started in 1978 in Bavaria. They reached a depth of 9.101 km. Information on this one is hard to find, at least in English, though there is a great Oilfield Review article (big pdf) [slb.com] available.
This Japanese project is going to drill through the sea floor in the Pacific, in a spot where the crust is thin, which will hopefully allow them to reach the mantle in only 7 km, under 2.5 km of water. For comparison: the previous record seafloor drill was only 2.1 km. So they've definitely got their work cut out for them.
Re:No (Score:3, Informative)
The liquid outer core is made of mostly the same stuff as the deep mantle, Iron with about 5% assorted dense metals mixed in. It's just hot enought to be liquid. The boudary region between them shades gradually from solid to liquid, so what we mean by outer core is essentially arbitrary. Geologists assign a level where it's 'liquid enough', as the boundary.
The solid inner core is a single Iron crystal. 1,500 Km across, and with damned near no contaminants. We guess this because earthquake waves passing through the inner core speed up if moving along the directions of the crystal lattices, and the pattern matches both it being a crystal and having the structure typical for iron at such enormous pressures. The boundary between inner and outer core is much crisper than the one between outer core and mantle.
Re:Energy (Score:3, Informative)
Temp ~6000K
Density of Iron 7800kg/m^3, Nickel 8900km/m^3
Diameter of outer core ~5000km
Mass of core = 5*10^24 kg, less than the mass of earth = 5.97*10^24
Heat content of core = 12*10^33 J, which combined with this data [ouc.bc.ca] of 12 trillion kwh electricity usage/year = 43*10^18 J/year gives us over a billion years to drain it 1%, well past the life of our planet.