Terraforming is “the deliberate modification of the physical environment to increase its habitability for humans”. (David, Leonard). The planet Mars could be terraformed more easily than other planets, as it is believed to be the most Earth-like planet. Hundreds of millions of years ago, Mars had an Earth-like environment, with a thicker atmosphere and more water. (Terraforming of Mars). Additionally, other similarities between the two planets lie in their temperature ranges, the presence of water, and the length of their days. Scientists believed that around 3.5 million years ago, "Earth and Mars may even have had similar ecological environments." (Explore space). Mars has the tallest mountain in the solar system, Olympus Mons, which is 27 kilometers high. (Interesting facts about the planet Mars). It is also one of the largest volcanoes in the solar system, with a diameter of 370 miles, "wide enough to cover the state of New Mexico." (Facts and information about the red planet). Like Earth, Mars also has canyons, including the Valles Marineris which was formed mainly by the tearing away of the Martian crust. Some canyons in the system are up to 60 miles wide. (Mars: facts and information about the red planet). We have also learned a lot about the composition of Mars thanks to the information collected during the missions. The United States launched Mariner 4 in 1964 and Mariners 6 and 7 in 1969, and these missions did not find life on Mars. These three missions were flyovers. Mariner 4 took the first close-ups of Freedman 2 on Mars. Sailors 6 and 7 analyzed the surface and atmosphere of Mars. From the photos taken, scientists realized that the dark features on Mars were not channels. In 1976, NASA's Viking 1 was the first successful landing on the surface of Mars. Clo...... middle of paper ......ce.com.Web. June 23, 2007. “Mars Exploration.” Wikipedia. Internet. March 11, 2014. Image from Mars Path. Extreme Tech.com/Inspiration Mars. Google Images. Web. “Lecture 25 Terraforming. Exoplanet.as.arizona.edu. Web. “Atmospheric Resources of Mars.” » NASA.gov. Web. “A nuclear fusion rocket could reach Mars in 30 days. » Espace.com. Internet. April 10, 2013. “Race to Mars.” Discovery channel. Web.Sharp, Tim. “What is the atmosphere of Mars made of?” Espace.com. Internet. August 3, 2012. “Terraformation of Mars.” Wikipedia. Internet. February 25, 2014. “Terraforming Deimos.” Terraformingwikia.com/deimos. “Terraformer Phobos” web. Terraformingwikia.com/phobos. Web. “The journey from Mars perspective to the Red Planet. » PBS.org. Explore Space.Web.Wall, Mike. “Curiosity makes a great discovery of water in the land of Mars.” Espace.com. Internet. September 26, 2013. Willett, Nicole. “How to Terraform Mars.” Hplus Magazine. Internet. February 19. 2014.