Images Dated 4th February 2004

Mars

Mars. Artwork of the planet Mars showingfeatures on its surface. At far left is thevolcano Olympus Mons. Standing 27 kilometres high, it is the largest volcano in the Solar System. Toits right are the three Tharsis Ridge volcanoes.From top to bottom, these are Arsia Mons, PavonisMons and Ascraeus Mons. To the right of thesethree volcanoes, the huge valley system VallesMarineris is seen running horizontally. The northpolar ice cap is seen at upper left. Mars is thefourth planet out from the Sun. It orbits some 228million kilometres from the Sun, taking just under687 days to complete one orbit

© Mark Garlick/Science Photo Library

Artwork of a satellite destroying space junk

Space junk demolition. Conceptual artwork of a satellite using a laser to destroy space junk. Space junk is an assortment of used rocket stages, old, dead hardware and other orbiting detritus which has been left in orbit by the hundreds of space missions since the 1950s. Destroying the junk by laser is just one idea about how to clear it. It has been estimated that there are over 20, 000 man-made objects in orbit, of which only a tiny minority are operational satellites. These objects pose a serious threat to further missions, as a collision with a delicate piece of space hardware could damage it severely. A collision with an inhabited craft could even prove fatal

© JULIAN BAUM/SCIENCE PHOTO LIBRARY

Comet nucleus

Comet nucleus. Artwork of the icy core(nucleus) of a comet. Comets are mostly frozenices (water, methane and ammonia) and dust, andthey are often referred to as dirty snowballs'.The nucleus of a comet can be many kilometresacross. Comets orbit the Sun, and are part of thedebris left over from the formation of the solarsystem. Large numbers of these objects orbit farbeyond the planets, well away from the heat of theSun. Some are disturbed from their orbits, andpass through the inner solar system where the Sunboils the ices into a coma (white). The solarwind blows the coma material into a tail millions of kilometres long, sometimes visiblefrom Earth

© Mark Garlick/Science Photo Library