Mars is the outer planet closest to us, and seems in some way most Earth-like: it rotates in a little more than 24 hours, it has a thin atmosphere and extinct volcanoes, and its inclination to the ecliptic is close to Earth's, creating seasons similar to ours (though nearly twice as long, since the "year" is also close to two of ours). The telescope shows white polar caps with seasonal changes, and its surface (see image below, from the Viking 2 lander of NASA) looks like windblown desert of the southwestern USA--a surface of boulders exposed by windstorms.

Maybe you should be grateful for NOT being there!    

If you were, you would need a spacesuit and a supply of oxygen, because the atmosphere is extremely thin (see tables) and consists essentially of CO₂. It is too thin to shield you in case of outbursts of solar energetic particles, though not too thin to support dust storms, which can last for weeks and obscure the face of the planet. Such storms frustrated astronomers when the first US orbiter of Mars, Mariner 9, started its observations.

    Kepler's laws later allowed the radii of planetary orbits to be calculated in units of the Earth's radius. It was then realized that by measuring any actual distance between planets in miles or kilometers--e.g. by the parallax method--would calibrate the scale of planetary distances in the solar system. Using a telescope, Jean Richer in 1672 obtained the first crude estimate of the distance of Mars, providing an estimate of the actual size in the solar system.

    Before astronomy had detailed information about Mars, it was widely held that life could exist on the red planet, or maybe actually did. Even through a good telescope, a 19th century observer of Mars could not resolve more detail than the unaided eye can of the Moon--and atmospheric variations ("twinkling") made the task even harder. Observers did agree about the polar caps and certain dark areas, but after that imagination often took hold. Some imagined seeing lines connecting darker areas--the famous "canals of Mars," supposedly belts of vegetation (like the Nile valley) along canals dug to distribute dwindling water resources.

    Percival Lowell, an amateur astronomer, whole-heartedly believed the reality of a Mars civilization. In 1893-4 he constructed an observatory under the clear skies of Flagstaff, Arizona, and in 1895 published the book "Mars" (later two more), with many maps showing such canals. Towards the end of his life (he died in 1916) he used his telescope to search for a new planet, and as will be seen, in 1930 it ultimately discovered Pluto.

    The notion of life on Mars also captured the imagination of fantasy fiction ("science fiction" was a later term). Edgar Rice Burroughs, creator of "Tarzan," wrote imaginative tales of a princess on Mars, now rightly forgotten. In 1897 Herbert George ("H.G.") Wells wrote "The War of the Worlds" about an invasion of intelligent Martians, which is still very readable (a film version also exists). In 1938 Orson Wells dramatized "War of the Worlds" as a radio broadcast report of an alien invasion unfolding in New Jersey, panicking listeners who had missed its beginning and imagined it was a real event.    

    Is there life on Mars? The Viking landers (1976) conducted elaborate biochemical experiments but so far have found no proof. Several NASA rovers have landed on Mars since then, most recently (5 August 2012) "Curiosity" with a mass close to one ton was landed in Gale Crater and is now (2014) slowly advancing towards Mt. Sharp.

    Interest was also aroused by some unusual meteorites recovered from the Antarctic icecap, said to have been ejected from Mars and containing tiny structures which some saw as fossils. So far, great doubt remains, but stay tuned.