Key Takeaways:

  1. Olympus Mons, Mars’ tallest mountain, might have been an ancient volcanic island surrounded by an ocean nearly 4 miles deep.
  2. Geological evidence suggests that the towering cliffs surrounding Olympus Mons resemble formations seen on volcanic islands on Earth, indicating interaction with deep ocean water.
  3. The mountain sits near the Tharsis Bulge, a massive volcanic plateau hosting several shield volcanoes, possibly formed by distinct regional plumes beneath Olympus Mons and Alba Mons.
  4. Evidence proposes a single long-lasting ocean on Mars, with its shifting shorelines attributed to mantle uplift deforming the planet’s surface and altering the ocean’s location.
  5. These findings shed light on Mars’ water history and suggest that as the ocean receded due to planetary changes, it marked a potential decline in the planet’s habitability.

Exploring Mars’ geological wonders has unveiled intriguing insights into the enigmatic past of Olympus Mons, the solar system’s tallest mountain. Recent revelations propose a fascinating narrative of this colossal Martian structure, indicating its potential origins as an ancient volcanic island surrounded by an extensive ocean.

Led by Anthony Hildenbrand of Université Paris-Saclay, a research team has unearthed compelling geological evidence suggesting that Olympus Mons might have once stood as a solitary volcanic isle amidst a vast, nearly 4-mile-deep ocean. The discovery emerged from the analysis of towering cliffs encircling the extinct volcano, resembling formations found on Earth’s volcanic islands like the Azores, Canary Islands, and Hawaii.

Standing a remarkable 16 miles tall above the Martian surface with a colossal base stretching about 374 miles wide, Olympus Mons hosts a volcanic caldera that last erupted approximately 25 million years ago. Situated adjacent to the Tharsis Bulge, a sprawling volcanic plateau housing other shield volcanoes like Arsia, Pavonis, and Ascraeus Mons, Olympus Mons bears similarities to these terrestrial islands.

The striking evidence lies in the form of massive cliffs, reaching heights of nearly 4 miles, enveloping Olympus Mons. Hildenbrand’s team asserts that these escarpments bear distinct characteristics resembling formations created when lava encountered deep ocean waters, estimated to have occurred some 3.7 to 3.4 billion years ago.

Previously, connecting these escarpments to liquid water had been a scientific endeavor, with unclear associations. However, the team’s findings suggest that these cliffs likely represent an ancient shoreline. Remarkably, the depression surrounding Olympus Mons today indicates that the ocean might have filled this area to a depth of 4 miles, supporting the volcanic island theory.

Furthermore, analogous features discovered on the northern flank of another Martian volcano, Alba Mons, over 1,100 miles away from Olympus Mons, provide additional evidence hinting at the extent of this ancient ocean.

View of a boulder-rich surface deposited by the older tsunami. These were then eroded by channels produced as the tsunami water returned to the ocean elevation level (white arrow shows flow return direction). Yellow bars are 10 meters. (Image credit: NASA/Alexis Rodriguez)

The formation of these colossal Martian volcanoes is attributed to hot spots in the molten mantle, generating convection that propelled warmer magma upward in towering plumes. Hildenbrand proposes that separate regional plumes likely underlie Olympus Mons and Alba Mons, distinct from those forming other nearby volcanoes.

This mantle activity not only led to the creation of the Tharsis Bulge but also significantly affected the planet’s crust, causing considerable deformation and potentially shifting the ocean’s location. Prior studies have identified two distinct shorelines in the Martian lowland Vastitas Borealis, initially interpreted as evidence of separate oceans existing at different times.

Contrarily, Hildenbrand’s team suggests a unified long-lasting ocean, proposing that the mantle uplift altered Mars’ surface, resulting in the ocean’s displacement and the observed two shorelines, separated in age.

This groundbreaking research not only sheds light on Mars’ intriguing water history but also hints that the planet’s potential habitability might have waned as the ocean receded due to planetary changes. If Mars ever hosted life, this era could signify a decline in its habitable conditions.

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