James Nicoll wrote:

At this point in time, Earth is the richest known source of
fissionables, although it seems reasonable that Mars might also have
ore beds. Io is probably worth a close look, as well.


ISTR biological processes had a part in concentrating uranium ore.

The conventional wisdom is that asteroids lack the geologic processes
that concentrate ore. I would imagine an ordinary chondrite is fairly
homogenous with various substances distributed evenly throughout.

But I don't believe this the case with a comet (or extinct comet) with
an eccentric orbit.

At perihelion internal heat and pressure can liquify volatiles creating
a solution of dissolved minerals & colloids. Brin's model of comets has
a mantle accumulating as surface volatiles are boiled or sublimated off.
I imagine the outer mantle to have vents and tunnels in it leading to a
more volatile rich center. These tunnels are likely narrow in some
regions and wider in others. In the wide rooms of the tunnel some of the
heavier particles might accumulate in a similar fashion to the the wide,
sandy regions of a river.

Hop