The main argument against terraforming Mars is its cost. Terraforming Mars could cost trillions of dollars, depending on the approach taken, and many question the logic on investing such significant resources in creating a new world, while humans and other animals continue to suffer on this world. This is an entirely reasonable argument, unfortunately we are not a reasonable species. Consider the costs of terraforming Mars versus the costs of the Iraq war and subsequent occupation, and then consider the short term and long term results of both.

The cost of terraforming Mars is justifiably difficult to calculate, but can be guessed at intelligently based on the historic and planned costs of space operations. The total costs of the International Space Station have been projected at $100 billion USD, by the time it is completed. NASA's Vision for the Future has a budget of $16.2 billion, and includes plans to develop a new generation of space shuttle, develop the Orion spacecraft, launch crewed missions to the moon by 2020, build a long term Lunar base by 2024, and launch a crewed mission to mars by 2037. If we calculate the cost at $16.2 billion each year for the next 28 years, the cost is approximately $450 billion. Meanwhile the European Space Agency (ESA) and Russian Space Agency (RKA), have been working on a couple of similar joint projects, the Crew Space Transport System (CSTS), and a joint mission to Mars circa 2030 costing an estimated $20 billion USD. The costs of the CSTS has not been finalized yet, but would if successful put Europeans and Russians on the Moon by 2024. Japan and China have also started working on separate missions to the Moon set for the 2020s. Canada has also discussed to option of joining the CSTS project or the Orion project.

For the cost of terraforming (to be technical caeliforming and ecogenesis) Mars we'll consider the above budgets, and attempt to reasonably calculate a projected total, ignoring inflation, which would need to be adjusted for in any long term budget. The primary requirement for any space activities is a launch vehicle, several of which exist, operated by the ESA, the US, Japan, China, France, Russia, India, Ukraine, Iran, and Israel. A secondary element is an Earth orbiting space station, however the ISS is only a research facility, and a larger station would be required, to house construction docks, and a large aeroponic facility. The construction docks would be to assemble large space ships from parts shuttled up from Earth, and the large aeroponic facility is to provide food, and recycle air and waste, thereby reducing the cost of ongoing operations. The next element required would be interplanetary ships, and Mars landers. As most of this is included in NASA's Vision for the Future, and NASA would only need to add the extra facilities to the ISS, lets use the figure of $500 billion, for the development and implementation of the first three required elements.

In order to facilitate terraforming, the construction of space stations in orbit of Mars and Venus would be required, as well as a mining colony on Ceres. Given the cost of the ISS, and the planned budget of a Lunar base is each approximately $100 billion each, the construction of these outposts should cost less than $500 billion. The station orbiting Mars is to serve as a delivery point for gas, water, and life being imported to the planet. The station orbiting Venus is there to skim carbon dioxide, and nitrogen from Venus' upper atmosphere, for shipment to Mars, and the base on Ceres is for mining water ice for shipment to Mars. Thickening the atmosphere, and building an ocean will likely take a century, so in order to cover ongoing costs, such as wages, and replacing equipment, let's use the NASA budget of $16.2 billion a year, for a century; approximately $160 billion, and then increase it to $250 billion to cover unexpected costs.

Transporting life to Mars will be the final major hurdle before colonization can begin, and this cost will be difficult to calculate, as it would depend on the lifeforms to be transported, which would depend on the success of the terraforming process overall. Nevertheless, given the preceding costs and the existing infrastructure (the ships and stations), $750 billion seems like a likely number, placing the entire cost of terraforming Mars at $2 tillion USD.

This number is only an estimate, however seems plausible. Two trillion seems an impossible amount of money, however, compare it to the cost of the Iraq war and occupation: $3 trillion USD, for the USA alone. This number does not include the costs to the UK, Australia, Japan, Korea, Italy, Spain, or the other members of the Alliance of the Willing. For the 3 trillion invested in occupying Iraq, the US could have terraformed (caeliformed followed by ecogenesis) Mars, had a station orbiting Venus, bases on the Moon and Ceres, and even a base on Callisto!

Consider the short and long term effects of both options. The Iraq war caused severe economic problems in the USA, and Alliance of the Willing nations. The cost of terraforming Mars would be spread out over a century, and therefore would not have had a significantly negative effect on the US economy, or on the economy of nations that participated. In the long run, Iraq's oil will be renationalized, and the democracy will only last as long as the people of Iraq value it; there are no long term benefits to Alliance members. Whereas a terraformed Mars could be sectioned up and sold to the highest bidder, generating income for the nations that terraformed it, and creating colonies, which could in the long run become member states of the US (or EU, Russian Federation, etc.), which would then be the homes of taxable citizens. Terraforming Mars would have undeniable long term benefits, both to the nations that invested the capital, and to civilization itself.

Finally, consider the political reality of both options. The invasion of Iraq alienated America from many of it's closest allies (Canada, Germany, France, etc.), and gave America's enemies fruitful grounds for recruiting new allies. If America had led the world into the sky, everyone would have wanted to follow in whatever capacity they had. The Europeans, Russians, Chinese, Japanese, Indians, Canadians, and Brazilians, would have wanted to participate as full partners. In order for most countries to participate at all they would have to reallocate large portions of their budget to aerospace, which in the case for most countries could have only come from cutting military spending. With all major powers involved in a new space race, there would have been little incentive to increase the military in smaller nations; the world would have been more peaceful. Instead we find ourselves in a new arms race, with our major economies on the brink of total collapse.

It makes one wonder why George W. Bush had a difficult time getting the $16.2 billion for NASA, when he got a bank check for Iraq.