[extropy-chat] SPACE: new planet?

Robert J. Bradbury bradbury at aeiveos.com
Fri Feb 20 22:39:58 UTC 2004

Harvey offered some comments on my comments about Kuiper Belt
objects, from which I will extract:

> These are older worlds that formed before our planets.

That really isn't clear.  This involves a very complex discussion
of the evolution of solar nebula and the star itself.  I do not
claim to be an expert in these areas but from what I have read
it seems to me that a lot depends on the density and material
structure of the nebula.  Depending on the conditions internal
structures (be they stars or planets) may aggregate before
external structures.  Or the conditions may be reversed.

If the star forms rapidly and heats up the nebula it may reduce
the opportunity for early external structure formation.  If
the star forms slowly, there may be a greater chance that
external masses may aggregate.

> About 10% of them have spawned moonlets which cause tidal forces that
> very well may heat up their cores to form a liquid internal ocean.

While I will grant that this is possible I haven't seen any papers
suggesting that tidal forces between planets and moons will provide
sufficient heat.  For example, it does not seem to be the case that the
moon is doing it with the Earth to a significant degree.  I have no
problem with the theory of the comment (for example Jupiter seems to be
doing it with Europa) -- I would just like a little bit more physics to go
along with the suggestion so one could quantify the extent of
gravitational heating effects.  Such information would be critical
to such areas such as the volume of an ocean, periods that it remains
unfrozen, etc.  We are having problems working these things out for
even Mars (when and for how long might it have had an ocean) which we
certainly have much more data about.  So raising these possibilities
for planetoids seems to be very risky.

Of course Harvey and I may differ on whether we will "colonize"
these planetoids or dismantle them but that is a minor difference
of opinion in the grand scheme of things.  The primary thing to note
is *where* the carbon on the solar system is likely to be and the
value of that carbon (from an economic or developmental standpoint).


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