Shaggy Visitors

Comets are small celestial bodies, which orbit the Sun along highly elliptical trajectories. They are divided into short- (< 200 years) and long-period (>200 years) comets. They have solid nuclei with diameters varying from hundreds of meters to several tens of kilometers, which contain water ice and other volatiles. When comets approach the Sun, these volatile compounds evaporate and stream ‘upwards’, carrying along solid particles. As a result, a coma of dust and gas, surrounding the nucleus, appears, and then the pressure of solar radiation turns it into a comet’s ‘tail’, also made from gas and dust. Comet’s nucleus matter is solid, but highly porous and fragile. Its surface is covered with fissures, depressions of irregular form, and various elevations. However unusual, from the point of view of terrestrial geologist, the conditions on the comet’s surface are, the geological processes, which ‘work’ there, are quite common. On the surface, solid matter becomes loose cover, which slides down the steep slopes. The resulting relief is defined by its resistance to destruction. These topics are the subject of the paper.

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