Mars

Mars, the first planet beyond the Earth in the Solar System, is easy to recognize because of the strong red colour which led to it being named in honour of the God of War. At its brightest it outshines every other planet apart from Venus. However, at minimum it may fall to the 2nd magnitude and is then easy to mistake for a star.

Earth and Mars are at opposition in positions E1 and M1 in the diagram (top). A year later the Earth has returned to position E1, whereas Mars has travelled just over halfway around its orbit, to M2. The Earth 'catches it up' at the next opposition, positions E2 and M3, roughly 780 days later. Opposition distance varies from 56 million km to 101million km (centre). The apparent diameter of Mars (bottom) ranges between 25?.7 and 3?.5. (Kerr, 528)

The gullies clearly visible in the wall of this impact crater are thought to have been formed by water. Debris carried with the water formed the lobed deposits at the base of the wall.

Mars at crescent phase, a sight never seen from the Earth. This spectacular picture was sent back from the Viking 2 spacecraft. The volcano Ascraeus Mons is conspicuous in the upper part of the daylight area. Closer views disclose the extensive cratering of the surface - a discovery that was made by the earliest space probes and that was completely unforeseen by Earth-based astronomers. (Chaisson 15)

Mars in general is not easy to study with a small telescope, but under good conditions, adequate instruments show dark, well-defined features and white polar caps. The dark areas were once thought to be old seabeds filled with vegetation but this attractive idea has now been disproved and as yet there is no firm evidence of any life on Mars. Some of the dark regions, such as Syrtis Major, are elevated plateaux.

The Martian 'day' is about half an hour longer than that of the Earth. The apparent drift of features across the disk is therefore obvious even over a short period of observation. Generally the atmosphere is transparent, except for occasional dust storms which may hide the surface features. (Comins,78)

The first reasonably accurate maps of Mars were drawn in the 19th century. In 1877 G. V. Schiaparelli, from Milan, compiled a chart and named the main features. These names have been generally retained, although recently modified in view of the space-probe discoveries. ...