Alan Erskine wrote:
"Larry Gales" wrote in message
news:Pine.WNT.4.56.0310022026410.1980@homecomps...

I am very much a fan of O'Neill colonies, but have long believed they
would be much easier if they were close to a carbonaceous asteroid rather
than the moon.


Why?

Here is one of my arguments for near earth asteroids:
http://www.clowder.net/hop/railroad/Gravitywells.jpeg

Another is, being recent immigrants from the outer solar system, they
are likely to be much more volatile rich than the moon. Air, water and
fuel might be easier to come by.



However, it would appear that Aluminum is perhaps the ideal
building material for a space colony and Nitrogen is a major part of any
atmosphere. So does anyone know typical concentrations of either Aluminum
or Nitrogen in near-earth asteroids?


Nitrogen content quite low due to the orbit - no atmosphere and no ice to
keep the nitrogen frozen.

As for aluminium, the concentration would probably be similar to the Moon.


It's thought that a good fraction of the asteroids are former comets
(One asteroid, 1979 VA, was actually seen as a comet with a tail in an
earlier sighting when it was named Wilson Harrington)

David Brin (he was a planetary scientist before becoming an sf writer)
speculated that as a comet's surface volatiles boil off, they leave a
tarry residue that is an excellent insulator protecting the remaining
volatiles at the center of the once outgassing comet.

1979 VA and Nereus are two asteroids thought to be ex-comets. Perhaps
there is ammonia in their interiors as well as water and some hydrocarbsons.

Hop
http://clowder.net/hop/index.html