Probing Of The Interior Layers Of The Earth With Self-sinking Capsules: http://www.cmp.caltech.edu/refael/league/radioactive-core-earth.pdf
It is shown that self-sinking of a spherical probe in the form of a capsule filled with radionuclides, whose decay heats and melts the rock in its path, deep into the Earth is possible. Information on the formation, structure, and shifts deep in the Earth can be obtained by recording and analyzing acoustic signals from the recrystallization of the rock by the probe.
Similar technology for penetrating ice:
A cryobot or Philberth-probe is a robot that can penetrate water ice. A cryobot uses heat to melt the ice, and gravity to sink downward. The difference between the cryobot and a drill is that the cryobot uses less power than a drill[citation needed] and doesn't pollute the environment.
A cryobot or Philberth-probe is a robot that can penetrate water ice. A cryobot uses heat to melt the ice, and gravity to sink downward.