Volcanoes on Mars

Named in honour of Mount Olympus, the lofty abode of the gods of Greek mythology, Olympus Mons is an extinct volcano on Mars which rises to a height of 25 km above the surrounding plains. This volcano is about seven times the height of Mount Etna in nearby Sicily or three times the height of Mount Everest.

Outlined by steep cliffs, Olympus Mons itself is about 600 km in diameter. If placed onto Earth it would cover the whole of France. These large volcanoes can exist on Mars because of the low gravity and lack of surface tectonic motion.

Olympus Mons is a shield volcano, built by fluid lava which slowly built up a very large volcano. Unlike the Earth’s surface, Mars lacks active plate tectonics and hence its surface is not subdivided into plates which move and create volcanoes, ridges and earthquakes.

However, it is thought that ‘Marsquakes’ may still occur very rarely since scientists have found evidence that not all volcanoes appear to be completely dormant.

Olympus Mons has been nicely photographed by Charles Galdies from Zenith Observatory in Naxxar, as shown above, using a 20 cm diameter telescope.

Its peak has peeked out of so-called orographic clouds which form adjacent to mountainous areas even on Earth as warm air is forced to rise by the mountain sides and thus it cools down and condensation occurs, creating these extensive cloud banks.

Although three times higher than Mount Everest, Olympus Mons would not be difficult to climb because the slopes of Olympus Mons typically rise very gently and so a climb to the top would only be a very long walk!

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Astronomical events this month

Mr Pace is president of the Astronomical Society of Malta.