The planet Mars: from antiquity to the present.

Mars has been a subject of wonder since earliest recorded time. Telescopic observations, from those of Galileo in 1610 to the end of the nineteenth century, were summarized by Flammarion (1892 and 1909). Modern observations began with Schiaparelli during the close opposition of 1877, the year when Hall discovered Mars' two satellites. The next 50 years saw the drawing of detailed maps by many astronomers, debates over the existence of features, and Lowell's advocacy of canals and intelligent life on Mars. Major compilations of knowledge of Mars were produced by Antoniadi (1930) and de Vaucouleurs (1954). Spectroscopic studies of the atmosphere led to the discovery of CO₂. Spacecraft have yielded enormous amounts of data that indicate a rich and diverse geologic history as well as many unsolved puzzles.