As a result, both planets have similar global atmospheric circulation patterns. In the early 1970s, when the Mariner 9 and Viking missions revealed huge dust storms on Mars, this led to computer simulations to determine how such large dust-loadings of the atmosphere would affect the surface temperature on Mars. Such computer simulations have also been applied to Earth's climate, loaded with airborne particles from a large nuclear weapons exchange. It was realized that the Earth's climate would be drastically affected by cooling and that nuclear war was even more of a no-win situation than previously thought. In the winter hemisphere, for example, waves of high and low pressure systems travel eastwards on Mars just as they do on Earth.
Fronts also occur on Mars.
Terrestrial storms occur in preferred zones, e.g., in the midlatitude oceans of the northern hemisphere. Computer simulations suggest that such Hadley circulation also occurs on Mars. In the past, geological evidence suggests that the Earth experienced climatic changes explained by alterations in its spin axis inclination and orbit. Likewise, geological evidence also indicates that Mars underwent similar climatic changes, albeit more extreme. Consequently, Mars is a natural laboratory in which we can test our climate theories.