Was Mount Olympus, the largest of the Martian volcanoes, a giant volcanic island in the past? The idea may seem surprising, but that’s what a new study published this week in the scientific journal Earth and Planetary Science Letters suggests.
The hypothesis it formulates is based on work led by volcanologist Anthony Hildenbrand, a CNRS researcher at the Geops laboratory (Géosciences Paris Sud) at the University of Paris-Saclay. However, this is not his specialty. What he usually studies are terrestrial volcanic islands, but the idea of ??working on the case of volcanoes on the red planet had been in his head for quite a while.
Surrounded by several colleagues, mostly from the same laboratory and some of whom – like Sylvain Boulet and Frédéric Schmidt – have long had Mars as their playground, he became interested in the most impressive of them, Olympus Mons, culminating at over 20,000 meters above sea level!
“What we observe on volcanic islands, during an eruption, is that the lava flowing from the top, when it comes into contact with water, suddenly accumulates creating a steeper slope just below sea level. Indeed, the water induces a very rapid cooling and therefore a massive solidification of the lava or, in any case, a drastic increase in its viscosity which means that it does not go very far », explains Anthony Hildenbrand.
There is a 5-6 kilometer high basal escarpment at the foot of the colossal Martian volcano. A circumference more or less concentric with the center of the mount that current studies attribute mainly to collapses of the external sides of the volcano. For the researcher, this explanation does not hold.
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In third place in the category “Planets, comets and asteroids”. From New Mexico in the United States, Lionel Majzik Mayhill captured a rare moment: on October 4, 2021, comet 4P/Faye split nebula Sh2-261 in the constellation of Orion.©Lionel Majzik
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Third place in the “Stars and Nebulae” category. This photo by Hungarian Peter Feltoti is a dive into the Heart Nebula, located in the constellation Cassiopeia 7,500 light years from Earth.©Péter Feltóti
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“First, when you observe a collapse on any landform, seen from above, it always forms a U, open outward. Which is quite logical since material was evacuated in the form of debris, to the outside, during the collapse. Now, what we see today when looking at the escarpment around Mount Olympus, apart from some small localized U-shaped collapses towards the outside, is on the contrary an inward concavity! Moreover, a collapse tends to create a fairly vertical cliff whereas the basal escarpment of Mount Olympus, whose sides are very gently sloping (about 5 degrees), has a steeper inclination… but which is only 20 to 25 degrees! »
If we add to this that it would take a collapse that occurred all around a volcano whose area is close to France and still at the same height, it actually seems quite unlikely…
