Here is a concept that has popped up once or twice on this board.<A HREF="http://www.thesahara.net/textpix1.htm"; Terraforming the Sahara</A

They guy who runs this site seems to have put in a lot of thought into this concept.

He also seems very idealistic, which is not a bad thing as long as an idealistic person does not stray far reality, as such people often do.

I first thought of this concept about ten years ago. It is good to see others have thought about it as well.

What we need to terraform the Sahara is a thick rainforest to lock in the moisture. Trees are very efficient a locking in moisture to an ecosystem. But trees need water. So how do we get it? From the oceans and seas around Africa.

There are two ways I see we could do it. One way would be to build desalination plant all around the coast in Northern Africa. I envision simple glass domes where the Sun evaporates the seawater, the vapor collects on the inside of the dome and runs down the side where it is collected and then pumped to the desert.

Another way would be with orbital lenses. These lenses would concentrate the Sun's rays into an ocean or sea where they generate huge volumes of water vapor. This vapor blows over the Sahara where it rains out. Perhaps orbital solar shades could help cool the air over the Sahara so that the vapor will rain out where it is needed.

Regardless of the method used, terraforming the Sahara Desert would be expensive and need the backing many nations. Perhaps this could be a world effort. Unfortunately, being a fan of Space Exploration, I have seen that most humans on this planet do not have the foresight or vision to see the benefits for such a project.

Perhaps after us humans turn the Sahara Desert into a United States size rainforest, we would then be ready to tackle Mars.