Re: [OT} Terraforming

>It depends upon air and water action against the rock, but
on this planet it
>took billions of years to create soil and organics. It will
probably NEVER
>happen on Venus, though there must be something like soil
in that corrosive
>atmosphere - its the organics that are missing.
Terraforming involves adding
>water and oxygen to a planet which otherwise would not have
them in the hopes
>of creating an environment that humans could live in
without major
>life-support. If you could replace the gas loss in the
atmosphere due to
>lower gravity you could conceivably terraform the moon.

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?