Mar

30

 Drilling to the earth's mantle and the Mohorovičić discontinuity was pursued by the USA back in the late 50s and early 60s under the name Project Mohole and then attempted by the Russians on the Kola peninsula in the 70s and 80s. Thoughts of drilling to the earth's mantle to find out what is there are being revived.

1) from a national geographic article:

It may not be a journey to the center of the Earth, but it could be the closest thing yet.

Scientists are planning to drill all the way through the planet's miles-thick crust to Earth's deep, hot mantle and retrieve samples for the first time. The samples, they say, would rival moon rocks for sheer scientific import—and be nearly as hard to get.

"That has been a long-term ambition of earth scientists," geologist Damon Teagle told National Geographic News. But a lack of suitable technology and insufficient understanding of the crust have long tempered that ambition."

2) Check out a second article in April 1961 Life magazine written by John Steinbeck during his time on board CUSS 1 at the start of drilling for Project Mohole.

Charles Pennington asks: 

The best place to drill, Teagle said, is in the mid-ocean,
because that's where Earth's crust is thinnest—only about four miles
(six kilometers) thick, versus tens of miles deep in continental
regions.

Is there some simple explanation of how we even know how thick the
earth's crust is and what's below it when we've never drilled through it
before?

Pitt T. Maner replies:

It's the depth at which the seismic velocity changes probably due to a compositional change to periodotite type minerals with perhaps some changes due to temperature regimes.

So the only samples that geologists have to look at from mantle depths were brought to surface enclosed in magma as xenoliths.

Other than that there are probably lots of questions as to what will be
found and whether the mantle differs from location to location in
composition.

One question they hope to find out is how deep life extends below the earth's surface.

A lot has been learned since I studied Geology 29 years ago.


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