Life on planets: habitability and exploration

¶ … life form found on Mars would be like. Mars is the fourth planet from the sun, while Earth is the third, so the planets are relatively close neighbors. However, the environments on these two planets are extremely diverse. Earth is a planet where life has evolved, while Mars is a barren planet devoid of life. However, if life could survive there, it would be extremely different from what we are used to here on Earth.

First of all, Mars has an atmosphere, like Earth does, but the Mars atmosphere is at least 100 times less dense than Earth's atmosphere. That means that the Martian atmosphere is not as protective as Earth's atmosphere, and that more of the sun's rays and radiation reach the planet. Mars does have enough atmosphere to create weather systems like clouds and winds, just like Earth, however (Squyres). Mars is colder than Earth because it is farther from the sun. Oxygen is not nearly as prevalent on Mars. Author Squyres continues, "The atmosphere of Mars contains much less oxygen (O2) than that of Earth. The O2 content of the Martian atmosphere is only 0.13%, compared with 21% in Earth's atmosphere. Carbon dioxide makes up 95.3% of the gas in the atmosphere of Mars" (Squyres). There is also atmospheric pressure on Mars, just like on Earth, but it is far less than on Earth, and it changes throughout the days and seasons, just like on Earth. Because there is much less pressure, winds are not as strong on Mars as they are on Earth.

Mars travels in an orbit around the sun, just like the Earth does, but it has a much larger orbit. A Mars year is 687 Earth days, and Mars has seasons, just like here on Earth. Because Mars is less dense than Earth, there is not as much gravity there, so people would feel as if they weighed less than they weighed on Earth if they were standing on Mars. The surface of Mars is made up of fine-grained dust, and dust storms are common on the planet. Mars also has many physical features like Earth, from deep canyons to volcanoes and large, smooth plains. There are many more craters on Mars than there are on Earth, indicating a more violent history of impacts from meteors and other space debris.

Mars also has polar ice caps, but they are made up of frozen carbon dioxide, rather than water. There is evidence that water once flowed on Mars, but there does not seem to be any water on the planet now. Scientists found a meteorite that had come from Mars in Antarctica in 1996, and they believe it shows signs of microscopic life on Mars. Author Squyres notes, "The evidence included complex organic molecules, grains of a mineral called magnetite that can form within some kinds of bacteria, and tiny structures that resemble fossilized microbes" (Squyres). However, not all scientists agree with these findings, and there is still not total agreement that there was once some kind of life on Mars. None of the spacecraft that have landed on Mars have found any evidence of life, either (Caplinger). Scientists do believe that Mars was much wetter in the past, and could have supported life, which could help back up the evidence from the meteorite. Another author notes, "Mars is almost certain to have been warmer and wetter in its distant past, so the existence of primitive life has been a tantalizing possibility for some time, but the real search may be just beginning" (Williams).

All of this physical and scientific evidence leads to a discussion of what type of life form might evolve to live on Mars. First, it would probably have to be a life form that lived underground or could burrow underground, in order to deal with all the dust storms that occur on Mars. It would also have to be able to endure large temperature differences, because Mars temperatures fluctuate widely. It can be 195 degrees below zero at the poles, and up to 70 degrees at the equator, so life would have to tolerate those extremes. The life form would probably be small, with six or eight legs that would allow it to dig and burrow. It would look like an insect with a very thick skin or shell, to help protect it from the winds, dust storms, and extreme temperatures. It would come out to forage during the day, during the warmer temperatures, and it would burrow deep into the Martian crust at night for safety and warmth. It would eat microscopic bacteria present in the Martian dust. It would be about the size of a large spider or beetle, and it would probably resemble one of those creatures. It would be reddish brown, to help it blend into the Martian landscape, and it would have large eyes and a keen sense of smell to help it locate the microscopic bacteria.