Evidence of another Climate

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Forward: The Ancient Martian Climate

In the early 20th century, a famous astronomer named Percival Lowell began observing Mars through his telescope. As he looked at it, he saw what appeared to be "several canals bordered by vegetation". These observations made many people believe that the conditions on Mars were not very different from the conditions on Earth. There was life on Mars, intelligence beings, and a livable climate.

Soon, however, these hopes were shattered by the first of the Mars probes. These Mars probes, such as Mars 1 and Mariner 4, 6, and 7, showed that conditions on earth were far from similar to conditions on Mars. The pressure on Mars' surface is less than .5% of the pressure on Earth. Also, because Mars is 50% farther from the sun, it receives only about 40% of the sunlight that Earth receives. As a result, the temperatures are so cold that they can freeze carbon dioxide solid. This frozen CO2, or dry ice, was found to be the main component of the ice caps on the Martian poles.

Also, there were extreme radiation hazards on Mars. This was because Mars lacked the protective barriers against radiation that Earth had. Two of the most significant barriers were:

Despite these discouraging results, Probes continued to be sent to Mars. Successors to these early Mars probes showed that Mars, although now seemingly dead and lifeless, once was very similar to Earth. When Viking 1 and 2 arrived at Mars, pictures of the surface were detailed enough to show many formations which could only be created by liquid water. There were many dried up riverbeds, which flowed in and out of craters that seemed to have been filled by water. Many of these craters had flat bottoms, suggesting that Rivers carried Martian soil and dust into the crater, which then settled onto the floor. Ancient Martian riverbeds carried water to and from large craters, which acted like lakes.

Another formation produced by water is what is called "Chaotic terrain". This "Chaotic terrain" was formed when underground water suddenly rushed up to the surface, destroying the land above and sinking it into the ground. This "Chaotic Terrain" is sometimes seen on Earth, but it is mostly a Martian feature.

The Viking landers also showed that water was once on the surface, when it reported that Martian rocks were composed of between 10 and 20 percent salt. Salts can only be formed when rocks are exposed to liquid water, which then allows the chemical reaction to take place. Also, the probes showed that sedimentary rocks were present on Mars. Sedimentary rocks almost always form at the bottom of large seas and oceans, as sediment slowly settles down onto the floor.

Even more evidence is found to support the theory that water was present on Mars, but this evidence was not discovered by space probes. In fact, this evidence was not even found on Mars at all, it was found on Earth! It was found inside small meteors that came from Mars, that had been recovered in Antarctica. These meteors showed two different things. The first, and the most famous by far, was evidence of bacteria found in one of these meteors. This will be discussed more in the Life on Mars section. The second piece of evidence comes from a chemical analysis of the rocks. When these rocks were analyzed, it was found that some were formed in cool, salty water, while others were formed instead an hot, mineral-rich water.

All of this evidence comes together to reveal quite a bit about Mars environment, both past and present. Mars did at one time have flowing water on its surface. Over time, almost all of the water either froze beneath the surface or was lost to space. The water that froze beneath the surface formed a layer of permafrost. Deeper still, underneath the permafrost, there may be some areas of liquid water remaining. This liquid water may be heated by geothermal energy, as we know that Mars is geologically active. Also, Mars had hot springs at one time (and may still have them).

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