There are entire cities in the Gobi desert. The population is one person per square km: http://www.britannica.com/EBchecked/topic/236545/Gobi/47958/People-and-e

There are entire cities in the Gobi desert. The population is one person per square km: http://www.britannica.com/EBchecked/topic/236545/Gobi/47958/People-and-economy http://www.britannica.com/EBchecked/topic/236545/Gobi/47958/... In the cities, you have to stay in a hotel because you're not allowed to pitch a tent: http://www.travelmarket.com/Gobi%20Desert/a-GOBI_DESERT/travelguide.htm http://www.travelmarket.com/Gobi%20Desert/a-GOBI_DESERT/trav... Colonies on Mars probably don't make economical sense currently, but the thing to keep in mind is that there are resources on Mars that no human or animal population is using. On Earth, it seems like anywhere you start digging you ruin someone's life. With eventual terraforming of Mars, we don't have to worry about accidentally de-terraforming China and Mongolia. We would have a free hand to change the atmosphere, melt the poles, etc. But ultimately Sterling's point on terraforming is probably true. We'll probably beat desertification long before we have the ability to terraform Mars.