I want to terraform Mars, but no rush...

Dr. Omni wrote:
> The most megalomaniac terraforming plans involve
>dropping comets in the Martian atmosphere instead
>of thickening it using local materials only.

A 20km comet body would be enough to do it. Actually, what this
means, is that 20 km of solid ice, maybe with N2 mixed in, so we're
digesting lots more cometary bodies to get this amount. Also, it's
probably better to drop it in little bites, instead of one big
lump...
A combination of mining Callisto, the belt, the Apollo/Amors, the
cometary cloud.
Hey, we're thinking the long term, here, aren't we?
Never mind the Zubrinites who claim we could have the global
temperature above frozen CO2 within 50 years of starting...

> there is also a "partial terraformation" plan that
>would involve vaporizing the soil (e.g., by using a
>giant concentrating mirror in orbit) and dumping
>zillions of tons of carbon dioxide into the atmosphere.

The best plans call for a multi-pronged attack.
1) Introduce perflourocarbons into the atmosphere (PFC, similar to
CFCs). Possibly methane based chemicals too. Zubrin says via surface
factories; I say it's far more likely, if we produce the stuff in
space, and drop it in via tether bucket brigades.
2) A statite mirror hovers outside Mars orbit around the Sun,
balancing solar sailing/magnetic sail against the solar & Martian
gravity fields. (L-1)
(of course, all the workers in the space factories live in O'Neill
habs...)

The mirror would focus sunlight on an area of the south polar cap.
This heats the local area a few degrees, to release some CO2. This
causes a minimal greenhouse effect, raising the global temperature a
few degrees.
The global increase caused by the PFCs and the local CO2 raises the
global temperature even a few degrees more, so that CO2 locked in
carbonate soils is released.

Within 50 years, this combined effort would allow daylight
temperatures through most of the Martian year above 0C, so we've got
water. Then we introduce lichens, cactus, algaes, etc.
At this point, humans can wear breathing masks, and cold weather
clothing, instead of full pressure or tension suits.
After another hundred years of plants eating up CO2, we might have
several times the present atmosphere (still far below what animals
would need)

This says nothing about raising the atmosphere so that humans can
breathe it, and nothing whatever about radiation protection.

Overall, I think it's worth it, but it won't be done with tiny loads
thrown from Earth by expendable rockets based on WWII long-range
artillery.
It'll be done only after the space going civilization can afford it.
Not that anybody'll need it: we'll have room for growth and social
experimentation aplenty, in space colonies.

The next big question is when can it start?
How long will it take us to thoroughly explore Mars, and say that we
completely understand it, so that there's nothing that Mars as it is
and has been can teach us?
Generations of specialist explorers having time & access to crawl
around & poke into everything. Hundreds of people on the planet,
living in cans & tunnels, breathing canned air whenever they go out.
Returning up to the O'Neill habs built in Martian orbit, fed by
Diemos & the asteroids.
Rehabilitating their musculoskeletal systems after a few months in
the low gravity with hard exercise. Study the data they got on their
last sorty to the surface, and prepare to replace the current
exploring crews on the surface.