Terraforming is “the purposeful alteration of the physical environment to increase its habitability for humans.” (David, Leonard). The planet Mars could be terraformed more easily than other planets because it is believed to be the planet most like Earth. In its early history, Mars’ environment was more like Earth’s, with a thicker atmosphere and more water that was lost over hundreds of millions of years (Terraforming of Mars). Additionally, Mars’ temperature range is somewhat similar to that of Earth, H2O (water) is present, and the length of the Mars day is close enough to the Earth day, so that organisms adapted to the Earth 24-hour day/night cycle could adapt to the Mars cycle.
It is believed that about 3.5 million years ago, Earth and Mars may have had similar ecological environments (Exploring Space). Some similarities are found in Mars geological makeup. Mars has the tallest mountain in the Solar System, the Olympus Mons. It rises up 27 kilometers above the surrounding plains and is a volcano that is about 370 miles in diameter (wide enough to cover the state of New Mexico) (Interesting Facts About Planet Mars). (Facts and Info about Red Planet). Like Earth, Mars also has canyons, including the Valles Marineris which was formed mostly by the rifting of the crust as it got stretched. There are individual canyons within the system as much as 60 miles wide (Mars: Facts and Info about Red Planet).
We have also learned a lot about Mars’ make up from information gathered on missions. The United States launched Mariner 4 in 1964 and Mariners 6 and 7 in 1969, and these missions found Mars to be a barren world, without signs of life. Similarly, in 1976 NASA’s Viking 1 was the first successful landing on Mars’ surface. Close-up pictures were taken of Mars’ surface, but they found no strong evidence of life (Exploration of Mars).
However, in 1971, Mariner 9 orbited Mars and mapped about 80% of the planet, discovering its volcanoes and canyons. In 2011, NASA Mars rover Curiosity investigated Martian rocks and was able to determine at a spot near its landing site called Yellowknife, was habitable billions of years ago.
To terraform a planet like Mars, the initial stages might take decades or centuries and to transform the entire planet into an Earth-like habitat would take several millennia (Lecture 25 Terraforming). Earth is currently in the tenth millennium of its terraforming era (David, Leonard). If Mars was at one time more Earth-like, millions of years ago, and has changed over the course of millions of years, it stands to reason that it should take at least one millennium, or 1,000 years to several millenia to terraform Mars so that it is once again more Earth-like. If we move too quickly, then we may end up with a runaway greenhouse effect, with higher atmospheric temperatures and evaporated waters. If we move too slowly, Mars may go through changes that might interfere with the terraforming...