Download So… how do we go deeper? So, the question is, how on Earth do

So… how do we go deeper?
So, the question is, how on Earth do we go deeper? Even if improvements in materials science
and nanotech can double the strength of our drill bits and strings, we’d still only be half way
through the crust, with thousands of miles to go before we reach the core.
So far, there only seems to be one semi-viable method — and it’s pretty wild. In two papers,
published in 2005 and 2008, two University of Sheffield researchers in England proposed a selfsinking nuclear capsule to explore the Earth’s interior. Their proposal is at the same time both
utterly crazy and yet delightfully simple. Basically, you get a foot-wide sphere of radioactive
cobalt-60, put it inside a tungsten capsule… and then just leave it to melt through the Earth’s
crust.
Cobalt-60, like most other
radioactive sources, glows
blue when underwater. This
is caused by charged
particles (i.e. radiation)
passing through the water at
a certain speed.
The cobalt-60 would be hot
enough to melt rock (around
1,000 Celsius),
while tungsten’s extreme
melting point of 3,400C
(6,150F) would enable the
capsule to withstand the
temperature of the Earth’s
mantle. The researchers say that the self-sinking capsule would reach a depth of 20 kilometers in
the first year, and then continue slowly on to a depth of 100 km over a period of 30 years. As the
capsule descends, it would leave a wake of molten rock that would then re-solidify, creating
sounds that could be monitored from the surface. These sounds would tell us about the
composition of the layers that the capsule passes through, in theory providing a lot more
information than our current methods of interrogating the Earth’s interior. The capsule itself
could also be equipped with sensors and the means to emit its own sounds, so that it could report
on its findings.
The paper doesn’t mention it, but presumably it might also be possible to trail a tungsten cable
back to the surface, for even better connectivity and reporting. It might also be possible to
“vacuum up” the molten rock as the nuclear capsule descends, though maybe a foot-wide hole
into the Earth would require some structural considerations. In 2003, a Caltech professor
proposed a similar idea, but by pouring molten iron into a crack in the ground, and then sinking a
probe in that molten iron, rather than relying on radioactive material.