Textbooks say that Mars is a world of wonders. Beneath its peach-coloured sky it has grand mountain ranges, deserts with shifting sand dunes, vast canyons that dwarf anything found on Earth and huge extinct volcanoes three times the height of Mt Everest.

But recently the orbiting Mars Global Surveyor spacecraft has shunned these wonders in favour of a small volcano that you could walk across in 20 minutes.

It is a small "shield" volcano and MGS has obtained the first close-up images of this type of structure. Planetary geologists believe that it may hold important clues about Mars's more active geological past.

Scientists say that it is similar in size and form to small basalt shield volcanoes found in Iceland and Hawaii.

But the Martian shield volcano appears to be different from its Earth cousins. It lacks the lava flows seen on Earth and has peculiar ridges.

Expert opinion is that the ridges are volcanic cinders from some past eruption that have been blown into ridges by the wind.