Terraforming Venus

In Poul Anderson's "The Big Rain," more than a million complicated airmaker machines on the Venusian surface break down paraform, yielding water. The formaldehyde reacts with ammonia and methane to produce hydrocarbons, carbohydrates etc for food, fuel and fertilizer. Carbon dioxide is broken down into soot and oxygen, the latter to be bottled for industrial use. Other substances are separated and collected to be processed in cities.

When seven million airmakers have been built, the atmosphere will be changed in twenty Earth years plus another decade due to factors like the law of diminishing returns and stratospheric gas never reaching the surface.

Artificially mutated, solar powered bacteria, living off carbon and silicon, release oxygen from rocks and ores. Pulverized stone and sand mixed with fertilizer become soil. Other engineered organisms will provide an ecology. Water brought to the surface by volcanoes is extracted from magma and hydrated minerals.

Hydrogen bombs exploded at selected locations will ignite the volcanoes while platinum catalyst sown by aircraft and Venusian lightning will attack the remaining poisonous gasses that will then fall as compounds in "the Big Rain," lasting ten Earth years to yield rivers, lakes and seas. With soil spread, bacteria, plants and animals released and heavy rain falling for centuries, reclaimed sections will get close to Terrestrial conditions in a hundred years and Venus might become a Paradise in five hundred.