The geography of out nearest planetary neighbour Mars is one of the most fascinating anywhere in the solar system with giant canyons, a strange bulge, signs of water in the distant past, mountain regions and icy caps. There have been many missions to the Red Planet in the last few decades, most notably the Viking missions of the 1970s and the entire surface has been mapped. Most people can name at least one feature and overwhelmingly that will be “Mount Olympus” or “Olympus Mons” – the largest volcano on the planet. What do we know about this behemoth?
1. It’s as Large as Arizona
Olympus Mons sits in an area full of volcanoes known as Tharsis Montes – there are eleven siblings and all of them are much larger than any volcano seen here on Earth. Olympus Mons is a god amongst these giants. Its base area is so large that it can just about fit inside the US state of Arizona. It is also slightly smaller than Texas and roughly two-thirds the size of France.
2. It dwarfs Mauna Loa
Mauna Loa is one of the volcanoes that make up the Hawaiian Island and is the largest (in terms of volume) active volcano on Earth, though its peak is lower than its neighbour Mauna Kea. Mauna Loa covers an area of 5721 square kilometres, and from base to peak is 9.2km. In comparison, Olympus Mons covers 295,254 square kilometres and is 22km from base to peak.
3. It’s Not the Tallest
Olympus Mons is not the tallest mountain in the solar system. That honour goes to Rheasilvia on the proto-planet Vesta. However, the difference in height between the two is only slight – both are estimated to be around 22km tall. Olympus Mons has the widest diameter making it the largest in terms of volume.
4. How Many Calderas?
Due to eruptions over millions of years, geologists have calculated that the volcano has not one but at least six calderas. Calderas are formed when the roof of a chamber collapses after it has expelled all of the magma inside it and each caldera represents a different phase of activity.
5. Size of the Caldera
If we take the caldera as a single entity, it is 80 kilometres wide. Somebody standing on the edge of one side will certainly not be able to see the other side. What’s more, continuing with Hawaii for comparisons, the island of Maui would fit comfortably inside the caldera. Yet surprisingly, it is not the largest volcanic caldera on the planet: that honour goes to one of its neighbours, Arsia Mons. Olympus Mons’ slopes are shallow – around five degrees which would make any climb up its slopes very easy. Take into account its immense size and the distorting factor of the curvature of the Martian surface and anybody climbing towards the peak is unlikely to notice anything – even from a distance. You may struggle to get up onto the slope in the first place as the cliff at its base is five miles high!