[extropy-chat] Rockets from the moon [was: something else but who cares...]

[J. Andrew Rogers]

Robert Bradbury wrote: 
> Interesting.  Eugen -- are you effectively saying that uranium
concentration
> is a process dictated (or influenenced) by water?  I'm not against this
> perspective I'm just interested in how significant a factor it might be.
> If it is significant then it may indicate that uranium mining on the
> moon may need to wait for nanotech.


While I don't know about uranium specifically, this view is probably
correct.

There is an increasingly popular notion (with plenty of supporting
evidence) in mineral exploration that surface concentrations of heavy
metals ("heavy metals" roughly meaning any metal with a density greater
than around 8g/cc) are generated almost entirely through the action of
hydrothermal systems.  This is true to a lesser extent with most metals,
but is particularly noticeable with heavy metals.  Without an active
hydrothermal environment acting as an atom transport, these metals won't
concentrate to any significant degree.  There are probably analogs of
these transport mechanisms based on other surface chemistries (e.g. sulfur).

Without intensive subsurface vulcanism acting over tens of millions of
years in a single location, and a water table to drive with all that
heat, one should not expect significant heavy metal concentrations.  One
of the geological features that makes, for example, the major gold
fields remarkable is that they are sitting on massive hydrothermal
systems that have been in continuous operation for very long geological
periods, which is not all that common.  In this sense, volcanoes are too
sporadic and short-lived.  Major rift zones (e.g. Nevada's Great Basin
region) typically provide some of the longest lived hydrothermal systems
and hence the best concentrations of heavy metals.

j. andrew rogers