Mars isn’t beachfront property, either: No liquid water has ever been detected on the surface. The atmosphere does contain a bit of moisture—enough that, if all gathered in one place and frozen, it would likely form a glob about as big as a medium-size iceberg.
When humans set up their first camp, as space buffs are sure they will someday, the weather will be nothing to write home about. The average temperature is no greater than -27° F (-32.8°C). Although it never rains, the poles do get some carbon dioxide snowfalls. Taking more than few gulps of air would ruin an astronaut’s day. Carbon dioxide, toxic to humans, makes up 95.3 percent of what little atmosphere there is.
A dune buggy drive across Mars would reveal a dramatic difference in scenery from the northern to the southern hemispheres. Much of the southern half is rugged, pockmarked with meteor craters dating from the planet’s earliest history. The relatively smooth plains of the northern half are believed to have been formed by ancient volcano flows and erosion. But the reasons for this difference remain under discussion. As do a lot of things about Mars.
