The Ancient Martian Climate

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Several million years ago Mars was very different. The main difference, beside the climate, was that Mars' axis was tilted by about 60 degrees. This was very unusual, because most planets' axis's are tilted very little. This unusually high tilt caused each Martian pole to be locked in a full day summer environment for part of the year.

With each pole being heated up that much for part of the year, no frozen CO2 could form on the surface for very long. With little or no frozen CO2 on the Martian surface, the atmosphere was much thicker. Also, because CO2 is a potent greenhouse gas, the Martian temperature was also much higher. It was so high that it could melt ice, and even produce water vapor occasionally.

With temperatures high enough to sustain liquid water, and pressures much higher than today, water flowed freely on the surface. As it flowed, it formed rivers across the surface, and lakes in many of the impact craters. On two very large impact craters, Hellas and Argyre, it formed vast seas. There might have even been enough water to fill the northern plains on Mars, creating a Martian ocean.

During the summer, enough heat was generated to evaporate some of the water in the oceans, lakes, and seas to produce clouds that rained over the rest of the surface. This produced a continuous flow of water (much like the flow of water on Earth), which created the features that many Mars probes have observed.

As this water flowed over the surface, some of its seeped into the ground. This groundwater collected into aquifers, or underground rivers. Sometimes, these aquifers would be heated by molten rock near a volcano, and produce hot springs. These hot springs might have enabled life to evolve.

During the Winter Solstice, the Green area has sunlight all day, and the Blue area has no sun. During the Summer Solstice, the Blue area has sunlight all day, and the Green area has no sun. The Yellow always has both Night and Day, but the Martian Poles are both in the Green and Blue zones.

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