Oceans of the Solar System - Ocean Worlds: The Story of Seas on Earth and Other Planets - page 240

radioactive potassium in the rocky core of Titan below its ice-water
mantle. The methane from such a deep source may then find its way
to the surface via cryovolcanoes, in which the 'magma' is water ice
warm enough to slowly flow (much as glacier ice flows on Earth) to
this moon's surface.
Titan is clearly active geologically. The dramatic scenery carved
by the rare, torrential downpours that punctuate the steady drizzle
are well preserved, and scarred by very few meteorite impacts. The
surface must constantly be being renewed with some version of
ice tectonics as well as ice volcanism. The ice sediment, too, must pile
up in strata that, like on Earth, must somehow be buried in sedi-
mentary basins. Here, in pore spaces between the sand-sized ice
grains, there will be the solar system's richest hydrocarbon reserves.
The northern hydrocarbon lakes lie in the low ground of a moon
that is slightly flattened at its poles. These lakes may not be so much
sitting on solid ice, but marking areas where a hydrocarbon table
(akin to Earth's water table) comes to the surface. Titan will be a
tempting target for far-future oil prospectors.
It is a target for prospectors of alien life of the present, too, both in
the surface ethane seas and in the subsurface water ocean. In the
former, there are plenty of complex organic compounds, including
tholins (complex polymeric nitrogen-containing hydrocarbons) pro-
duced by photochemically driven reactions in the atmosphere. There
is none of that supremely universal solvent, liquid water, at the surface
however—it is simply far too cold—and it is a moot point whether
Titan's liquid methane and ethane would allow the kind of complex
and self-organizing chemistry that has made life possible on Earth.
However, the subterranean sea is water-rich, and this moon's active
geology has almost certainly enabled some kind of cycling to take
place between the interior and the organic-rich exterior. Such a link is
a potential key to life.