Elon Musk has recently brought an idea of multi-planetary civilisation as a serious near-term issue. His goal is to establish Mars colony by 2023 and later retire and die in Mars. He has also envisioned the idea of larger scale Mars-colony. Last week he talked about 80 000 Martian citizens as realistic near-term goal if reusable launch vehicle succeeds. Now he has upgraded his vision into millions!
However, I think that there is not much prospects for large scale civilisation in Mars, because environment is just too hostile and energy production is a real issue, because winter in Mars is very long and dim sun could be blocked by dust storms that may rage for months. Therefore there is no life in Mars without nuclear energy and nuclear energy in large scale is just impossible with current technology. Installation costs of nuclear power in Mars are probably some few millions per kW and advanced LFTR concepts may reduce the cost just by one order of magnitude. There is also minor ethical issues to launch fully loaded nukes from Earth. However, there is no need to discard dreams of multi-planetary civilisation, because we have better place for large scale colony than Mars. That is Earth's sister planet Venus. Venus has mostly ignored in Scifi, after it was discovered that the surface is utterly inhospitable. However, this wrong, because the conditions at upper atmosphere of Venus are perfect for large scale floating human colony. These conditions at 50 km altitude are very Earth like, unlike the hostile conditions in Mars. Of course for short term goal, small Mars base is essential. Also we might need a semilarge Mars base to supply large scale Venus colony. Fully reusable rocket should be rather easy to maintain in Mars, because gravity well is significantly weaker. Therefore it is just cheaper to export essential goods from Mars to Venus than from Earth. Venus has not much to offer, other than the second home for earthlings. Even science is rather dull basic research. Mars has at least prospects for (ancient) life and interesting geology. However for the purposes of colony, the most important resources in Venus are very abundant. Most importantly there is a huge flux for solar energy. More than double that of what there is in Sahara. And it is also useful solar energy, because light is indirect and scattered from clouds and outside temperatures are cool enough (ca. 0-20ºC). Indirect light and cool temperatures are essential for PV-cells, because their power output and durability is depended on the temperature of cell. Therefore the cost of energy in Venus is essentially zero and thus Venus might be cheaper place to live than Earth! For other essential resources, Venus has lots of oxygen and nitrogen for breathable air. It is also possible to boost lifting abilities with helium that is also relatively abundant in Venus. However Ni-O is by itself very strong lifting gas, so it is no problem to create floating cities. Most of the corrosive sulphuric acid haze is between 20 km and 40 km. It can be harvested and used as a hydrogen source. This means water and it is a basis for organic and inorganic chemistry. Infrastructure in Venus is mostly carbon, aluminium and silicon based. Other metals must be imported from NEA-asteroids and from Mars, because their concentrations are too low in Venus crust for practical mining purposes that are not too pleasant. However, carbon fibres are very versatile materials, therefore abundant basic materials: carbon, oxygen, nitrogen, hydrogen, silicon, aluminium and magnesium are more than sufficient for colonisation purposes. When the space infrastructure is established, it is not too expensive to utilise asteroids as source for rare metals. We must just replace steel as a basis of civilisation with carbon, aluminium and silicates. This is possible, because the cost of energy is practically free in Venus. —Jouni Reference: Colonization of Venus By Geoffrey A. Landis (2003) http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030022668_2003025525.pdf
