On 6 Dec 2009 at 16:35, Tim O'Reilly wrote:
> For my 2cents worth I figure the 'mining' laser would also be used in
> the prospecting phase of things as it melts/vaporizes a portion of
> the material and would allow for spectral analysis.
> While many asteroids will be nickle-iron, chondrites (sp?), or even
> more akin to the iceballs that are thought to be the primary form of
> comets (iceballs-plus?) those are not the only kinds. The metorite
> that caused the air-burst explosion in Siberia left traces of iridium
> IIRC and it is supposed to be a large metorite that is the source of
> the USSR's supply of titanium. They certainly have an abundance of
> the metal that others do not considering that they were able to build
> a number of submarines using it for the hulls (Akula class I
> believe). So while the iron-nickels, stoney, and ice-balls may
> predominate they shouldn't be the only ones.
"Nivkel-iron just means that's the predominant components. There are
a lot of other elements in there in small amounts (which add up fat
in a large body). Iridium is one of them. Most of the iridium in
Earth's crust is meteoric. The iridium from when the planet formed is
down in the core.
Titanium isn't all that rare. It's just a pain to extract and more of
a pain to machine and form.
> Consideration could also be given as to how the asteroids in a
> particular system were created... are they 'left overs' from the
> creation of teh planets in the system? Are they the remnants of a
> planet that was destroyed? (was the planet ripped apart by a couple
> of jovian class planets getting to close or some super eco disaster
> or war by an earlier race?)
Ripped apart planets are unlikely. Except as the result of
intelligent life form deliberately destroying one (which is a lot
harder than you think.
They'll have some ore bodies from the remnants of the crust. The
deeper stuff (from the mantle and core) are going to be a lot less
differentiated.
The types I mentioned are the result of the way systems form from
interstellar dust and gas.
Icy bodies form.
Then if they are at all large, the heat from the radioisotopes in the
"dust" will cause the body to melt inside. Rememver that the clouds
are usually compressed to the point where they start forming systems
by shock waves from nearby supernovas. So they'll be a lot richer in
short lived isotopes than our system currently is.
Small ones will be "dusty snow" with an ice core.
Bigger, you get ice crust over liquid (water/ammonia/[methane?]) with
the dust settling to the core. The liquid will slowly freeze from the
center in, while the core may actually get hot enough in the center
(still from radioactive decay) to dry out and melt. That gives you a
stony core.
Even bigger ones will have the molten stony core have nickel-iron and
other elements that will dissolve better in that separate out as an
inner core.
Eventually things cool off and freeze thru. Smaller bodies first.
Collisions will break things up, given you chunks of the various
layers.
If you are close enough to the star the icy parts melt and evaporate
the lighter things, while the more complex things react with UV to
form really complex stuff. That's where you get the carbonaceous
chondrites (CHON from C, H O and N, the symbols for carbon, hydrogen,
oxygem and nitrogen, the primary components of chondrites)
> When novas and supernovas go off the
> planets of nearby systems must take a pounding, what was the original
> class of the planet (sub-jovian, jovian, terran, venutian?) what is
> left after the nova radiation and blast front passed through?
> (asteroids, barren airless, tainted thin, what else may have occurred?
Novas won't affect anything outside the system they occur in.
Supernovas will have varying effects up to hundreds of light years
away.
> Since traveller essentially is hand-wavium in any number of essential
> respects one need not hold too tightly to any specifics but apply
> ones imagination ... what would happen to an essentially iron-nickel
> asteroid that got caught 'to close' to such a stellar event? Would
> it be compressed in some manner?
Nope. Not even if it was in the same system. It might melt over
evaporate some, but there just isn't enough *density* in the
gases/plasma going past to apply significant pressure.
But you might get a lot of *really* interesting elements deposited on
it from the cloud. That's the premise of one of Poul Anderson's
novels.
> iron-nickel asteroids of sufficient size could be worth quite a bit
> in and off their own right, at least they were out of some planets
> gravity well and therefore somewhat easier to haul to a space based
> refinery/manufacturing center.
Well, consider that a cubic kilometer of nickel-iron asteroid is
about 8 *billion* tonnes. And if only 1 *millionth* of that is (for
example) gold, you are talking about 1000 tonnes of it. Which is
billions of dollars at current prices.
--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com