Mars had tsunamis propelled by landslides.
When all of this material fell into the water of the ancient ocean of Mars, it created a mighty tsunami that stretched between 25 and 43 miles long and smashed into the coast of the planet’s northern hemisphere. Martian tsunamis are not a new idea. In 2015, researchers showed that impacts from space had splashed into the planet’s ancient ocean and raised giant waves. The latest findings could also help planetary scientists determine how big the ocean might have been.
Mega-waves on Mars
To show the same thing that could have happened on Mars, de Blasio studied satellite images of the planet’s topography, more specifically the remains of the massive landslide. Measuring 370 to 430 miles in length, the scar is “probably the largest landslide deposit on Mars,” she says, and possibly the longest landslide in the solar system. When these rocks tumbled down the mountain billions of years ago, De Blasio argues, they smashed into the water to create a huge wave that rushed over the landscape. As the tsunami progressed, the rocks scraped the solid ground below.
The sandy and muddy waves left their fingerprints on the shoreline far from Olympus Mons. De Blasio identified the fingerprints, then used models to verify that the waves could have traveled several hundred miles. Mount Olympus towers over the Martian landscape, reaching a staggering 15 miles high. The largest is the western aureole, a ring of fine-grained rock around the volcano that covers the land to the north and west.
The region was created by a single massive landslide. Studying the region on the outer edge of the extensive landslide, de Blasio noted that unusual deposits marred the ridge. Using images from NASA’s Mars Reconnaissance Orbiter and Mars Odyssey satellites, he studied the surface to better identify features at the edge of the landslide. The rough surface suggests the presence of ridges created as the rock slide slowed.
As the flow of material encountered a ridge known as the Acheron Dorsum, the material began to rise, creating pressure ridges that move closer together until eventually the landslide stops. When the tsunami slammed into the back of Acheron, the sandiest and thickest components fell from the wave first, creating a smooth layer.
A controversial issue
If the features that de Blasio has identified were sculpted by tsunamis, then they are a strong argument for the presence of an ocean about 3 billion years ago, when the solar system was only 1.5 billion years old. But even with the huge waves, an ocean is not a certainty. Another possibility is that the landslide melted the ice that was at the base of the volcano as it traveled through the icy terrain. Instead, he thinks the tsunami reservoir is inconsistent with the hypothesis of a large Martian ocean in the northern hemisphere.
“The existence of a Martian ocean is a controversial issue that is extremely relevant to the evolution of Mars,” says De Blasio. “The possibility that an entire ocean drives the hydrology of Mars, with its corollary of lakes, rivers and a humid atmosphere, is of great importance.”
