Labels: text | machine | screenshot | wheel OCR: FIRST OBSERVATIONS OBSERVATIONS OF SPACE PROBES THE CANALS OF MARS OBSERVATIONS OF SPACE PROBES Eventually it was shown that the dark lines called canals were actually an optical illusion due to imperfections in early observation instruments. Various experiments showed how the mistake was made: Untrained observers were shown diagrams of disconnected figures or dark dots from a distance. When asked to draw what they saw, they very often linked the figures or dots with straight lines. But the canal theory was finally put to rest by the Mariner 9 space probe in 1971. When the Mariner 9 photographs were compared with Lowell's maps, there was very little correlation. Mariner 9 did, however, show that there are spots and lines on the surface of Mars which change with the seasons. In all likelihood these formations are composed of windblown dust, much like sand dunes, whose arrangement varies with seasonal winds. But the lines bear no resemblance to canals and their positions change. Furthermore, it is highly improbable that the surface of Mars changed fundamentally between the time Lowell made his observations and the Mariner 9 program. MARS BETAT
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