Mount Olympus could be an oceanic island on Mars three billion years ago

portada volcan Olimpo Marte

Evidence is accumulating that early Mars was blue. However, the implications that an ocean would have on local orography has not been studied in depth. For this reason, a new article is now published that analyzes these consequences on Mount Olympus on Mars. And the result is striking, the largest volcano in the Solar System could have been an oceanic island.

Topographic profile of Mount Olympus
Topographic profile of the Olimpo Volcano according to the study and references to the main morphological characteristics

Where is the water on Mars?

One of the biggest mysteries of Mars is what happened to its water. We have one slight idea that the lack of gravity led to the loss of atmosphere and the solar wind swept its surface of volatiles. To do this we need to better typify where that water was, but it is not a simple process. To begin, we must chronologically date areas that we can confirm had water, and that is two problems for lack of one.

That is why this study focused its attention on Mount Olympus, volcanoes solve both mysteries. Firstly, because of the rocks expelled in eruptions, it is possible, through radiometric dating, find out your age. And second the sedimentation processes, the way rocks accumulate change abruptly depending on the environment. That is, if the eruption is underwater, they will accumulate in one way, and if it is on the surface in another. Furthermore, in the case of oceanic islands it is typical to find large slopes that mark the coastline.

image of the Tharsis volcanoes
Image of the Tharsis region with the Lowlands to the North, and the Highlands to the South, Olympus Mons is the largest in the image. Source: ESA

The geological history

The volcano is located in the Tharsis region, famous for its volcanoes, although none come close to the size of Olympus. Also, it is well recognized geologically for being the connection between the Low Lands and the High Lands of Mars.

Previous studies of the volcano dated its greatest growth to more than 2.54 billion years ago. But, there is a record of volcanic activity between 3.8 billion years ago and less than 10 million years ago. Geologically speaking, this is very recent, at that time on Earth the continents almost entirely occupied their current positions. The only notable feature that would be absent in that would be the union between North and South America. Even biologically speaking, it is relatively recent, with horses and other large mammals already existing. 

Submarine aerial sedimentation
Aerial-submarine sedimentation

Why could it be an island?

There is something very important in planetary geology: analogues. Geological processes tend to be the same on Earth and Mars, and although they can cause serious errors, they remain a cornerstone of research. In this case, Mount Olympus has many of the characteristics that oceanic islands have. We also know that there, in the lowlands of Mars, there was an ocean at the same time the volcano was forming.

From the analogues on Earth, for which the Canary Islands, the Galapagos or the Hawaiian archipelago among many others can be used, we obtain information on the change in air-water sedimentation. This limit can reach more than 15º between sub-oceanic sedimentation and terrestrial or aerial sedimentation.

Elevation mechanism of the Olympus volcano
Lifting mechanism of the Olympus volcano according to the study

A dizzying climb

The study faces a serious problem with one of its main supports, the height of the vertical cliffs on the edge of the volcano. They have had to be creative when it comes to finding an answer because their 6 kilometers of height are more than double what is possible for an ocean on Mars.
They propose that the lithosphere would have sunk due to the weight of the island-volcano during its growth. Later, once the ocean retreated or evaporated, an uplift mechanism would have occurred caused by swelling of the subsoil due to the appearance of magma. It would be associated with the formation and growth of the ascension of Tharsis. And in recent times the eruptions would have provided a last layer of residual height but of lesser importance.

Martin Morala Andres