The images of New Horizons from Pluto will take more a year to arrive from space, for the moment with have some compressed images as a preview.

Nasa has advanced some information regarding the geologically inactive zone, but there has been no information regarding the possible geologically active zones, on the formation of the plateaus and the mountains.

What forces could be driving geothermal activity of what nature on Pluto? What can be learnt from theories of the moons of Jupiter and Saturn to understand activity inside of Pluto? What is the theoretical temperature of the center of the dwarf planet?

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Geothermal activity can originate from a combination of:

  1. Residual heat from planet formation: During the formation of a planet, half of the potential energy of the parent region of dust and gas can be theoretically converted to kinetic energy---this is known as the Virial Theorem. The kinetic energy of the particles translate to a temperature.

  2. Internal radioactivity: Around half of the $4.5 \times 10^{13}$W of heat that come from the Earth's interior is driven by radioactive decay. Should Pluto have the same proportion of radioactive materials in its composition? Some would assume so, but others would say that the heavier radioactive materials should have fallen towards the centre of the solar system during its formation and would thus exist mostly in the inner planets. Note that geothermal activity on Mars has now ceased despite it being much larger (Mars has a radius of $3400$km while that of Pluto is $1200$), so a combination of residual heat and radioactive decay is perhaps unlikely in the case of Pluto.

  3. Tidal effects: Tidal forces basically apply whenever a part of a planetary body experiences a changing gravitational field with time (see tidal heating)---a number of processes can cause this:
    • the moon having an elliptical orbit;
    • extra moons in the vicinity (relevant to Io);
    • moon's orbital period and planet's rotational period not being synchronised;
    • non-uniform density in planet.

With time, the New Horizons mission should shed more light on these $3$ possibilities.

Note that the geothermal activity on Pluto likely refers explicitly to substances such as Nitrogen, Methane, etc., where far less energy is required to drive activity; that is to say, the ability to melt silicates has long since passed.

  • 1
    $\begingroup$ A goodly sized impact might also drive boiling and convection cell formation in mixed methane/nitrogen ices. With such low heats of fusion, these substances might well cover any evidence of an impact crater that sets them to vaporizing. $\endgroup$ Jul 25 '15 at 16:53
  • $\begingroup$ Carbon monoxide. Forgot carbon monoxide. Low heat of fusion; there's a goodly deposit of that on Pluto as well, in Tombaugh Regio : planetary.org/blogs/emily-lakdawalla/2015/… $\endgroup$ Jul 25 '15 at 17:57

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