Olympus Mons: The 25km High Volcano on Mars May Have Once Been Surrounded by a Vast Ocean.
When Mars was young and humid billions of years ago, the massive Olympus Mons volcano may have resembled the Stromboli or Savai’i volcanoes on Earth, but on a much larger scale. A newly published analysis in the journal Earth and Planetary Science Letters highlights many similarities between Olympus Mons and active volcanic islands on Earth, providing further evidence of Mars’ watery past, as reported by Science Alert on July 27.
Olympus Mons on the surface of Mars. (Photo: CNRS)
According to a research team led by geologist Anthony Hildenbrand at the University of Paris-Saclay in France, the steep cliff rim, which is 6km high, surrounding Olympus Mons likely formed from lava flowing into liquid water when this structure was an active volcanic island during the late Noachian and early Hesperian periods.
Olympus Mons is a shield volcano soaring 25km high, covering an area comparable to Poland. It is not only the largest volcano but also the tallest mountain in the solar system. However, its base does not meet the ground like a gentle slope. Instead, at an elevation of about 6 km, there is a steep cliff that encircles most of its perimeter, dropping straight down to the surface below. The origin of this steep cliff remains a mystery.
Today, Mars is barren and dusty. Water on the planet’s surface exists only as ice, with no rivers flowing and no oceans covering vast basins and craters. Yet, researchers are increasingly finding evidence that reveals Mars once held significant amounts of liquid water. The Gale Crater, where the Curiosity rover is currently operating, may have once been a vast lake billions of years ago.
Hildenbrand and colleagues used this data to reconstruct the environment around Olympus Mons. They examined similar shield volcanoes on Earth, specifically studying three volcanic islands: Pico in Portugal, Fogo in Canada, and Hawaii in the United States. The research team found that the coastlines of these islands feature steep cliffs, similar to the cliffs surrounding Olympus Mons. On Earth, such steep cliffs result from changes in the viscosity of lava due to temperature differences when transitioning from contact with air to water. Therefore, the researchers speculate that Olympus Mons may have been a volcanic island surrounded by liquid water.
The research team suggests that the height of the steep cliffs could represent the former sea level of a now-lost ocean. The period of lava flow, occurring 3 to 3.7 billion years ago, coincides with the existence of oceans. “Future spacecraft designed to collect samples or autonomous robots could assess dating at various locations on Olympus Mons, promising significant research potential,” concluded Hildenbrand and colleagues.
