Venus

If one does not insist to go down to the solid surface (500°C 90bar) Venus is actually a nice place for humans to colonize (52.5km 37°C 660mbar). And this will be rather easy with nanofactories since Venus' atmosphere is is essentially an ocean of building material bathed in intense sunlight.

Breathable air and nitrogen are effective lifting gasses in the dense carbon dioxide atmosphere. Comparison of molecular weights: nitrogen 28, oxygen 32, carbon dioxide 44

Atmosphere

The atmosphere is not your foe its your friend. She ..

• .. provides building material in optimal standardized form
• .. makes the scarce hydrogen better available (sulfuric acid rain is a natural hydrogen concentrator process)
• .. provides radiation protection (except UV)
• .. provides protection against micrometeorites
• .. makes street infrastructure unnecessary
• .. provides an environment with nearly constant temperature
• .. to a degree protects from volcanism on the ground

Colonisation - (conceptual)

The objection is to create a nice place for humans to live.

First a nanofactory (e.g. of the size of a sugar cube) is sent to Venus. There a durable balloon is created with a semitransparent diamond solar foil on top that leaves through enough light for plants to grow. The ballon further needs an "atmospheric converter unit" (air using micro ships) that has a number of functions. It creates among other thing breathable air.

Creating earth like soil with humic substances such that plants can grow in a natural way takes a lot longer then the employment of such a balloon. One could start with hydroponic cultures and compose the dead plants. A small piece of earth soil may be usable to introduce a rich set of microorganisms.

Atmosperic converter unit

• filters nitrogen from the atmosphere
• captures sulfuric acid rain which concentrates the rare hydrogen [Todo: at which heights is sulfuric acid rain present]
• sulfuric acid → hydrogen + sulfur dioxide
• carbon dioxide + hydrogen -> ethyne + oxygen

Possible threats

• Lightning
• Wing gusts (danger of toppling over)

Fires

Building a thin walled carbon balloon filled with oxygen is basically asking for fire. To mend this problem one can compartmentalize bigger balloons and fill the uninhabited parts with nitrogen.

An other approach is to use silicon carbide as a building material which may self protect against fire by building glass. For silicon one would need to mine the surface though. To get rid of the excess oxygen from the silicates (releasing it to the atmosphere might get dangerous after a very long period of such pollution) one needs to use iron. The place where one can get unoxidised iron for sure is the planets core. (See: deep drilling)

A closed material "cycle" can be conceived that protects against fire even if atmosphere gets really crowded.

• carbon dioxide + silicate stone → silicon carbide + oxygen
• oxygen + iron → iron oxides
• sulfur dioxide + iron → pyrite + iron oxides
• sulfuric acid + oxygen → hydrogen + sulfur dioxide