Terraforming Mars. Artists impression of a vast greenhouse built on Mars to assist plant growth. The greenhouse would enclose several thousands of hectares of the surface, and would be one of many such buildings around the martian equator. The greenhouse is needed to provide a suitable temperature and atmosphere for plant growth; the mean surface temperature on Mars is about 55 Celsius, but has a daynight range of several tens of degrees. The atmosphere on Mars contains about 95% carbon dioxide, but at a pressure of 0.007 Earth atmospheres. Such buildings might also be home to about 250,000 settlers.