Re: [OT} Terraforming

G'day Laserlight,

>Actually what I mean is:
>Say humans land on a world with a respectable amount of
>atmosphere and water, but no life.  You can break up some
>rock and add organics (compost) to get soil, but obviously
>you can't add enough organics to get topsoil for the entire
>planet.  Therefore you use....what?  Algae?  Lichen?  What
>breaks down the rock, and how long does it take?

Its been a while, but as far as I can remember you want microbes
(aerobic
and anaerobic bacteria), meiofauna (little itty bitty critters in the
siol), worms would be good too. Lichen is good on rock, but it probably
be
best to do some wide scale pre-emptive smashing into smaller pieces
first.
The presence of water by itself should have created sand banks etc as it
eroded the rock so you may already have a basis to work off. After that
you
need plants as the roots break-up the soil and return some organics, and
legumes would be good as they have natural N fixation (assuming your on
a
planet which has free N in the atmosphere). Now as to how long, depends
on
how hard the rock is (how friable I think the term is) and how much
pre-emptive smashing you do so anything from a decade to millenia
(probably, as far as I remember).

Hope that helps

Beth

P.S. Giving the critters some top soil as a "base" to work from may also
increase the rate of the process. 

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Elizabeth Fulton
c/o CSIRO Division of Marine Research
GPO Box 1538
HOBART 
TASMANIA 7001
AUSTRALIA
Phone (03) 6232 5018 International +61 3 6232 5018
Fax (03) 6232 5199 International +61 3 6232 5199

email: beth.fulton@marine.csiro.au