Mars Express reveals 'halo' on Olympus Mons — and it's huge

This aureole encompasses the volcano's basal scarp, a rugged perimeter characterized by a high degree of steepness, reaching up to seven kilometers in certain areas.

Within these images lies a captivating tale dating back 100 million years. The aureole tells the story of a cataclysmic collapse that shook Olympus Mons's lower slopes, triggering a sequence of events that shaped its current landscape. 

Large amounts of lava once flowed down the volcano's flanks, initiating landslides that descended to meet the bedrock beneath – a bedrock laden with ice and water.

As the searing lava encountered the ice, it melted and destabilized, prompting a section of Olympus Mons's rocky rim to fracture and detach.

This monumental collapse materialized in the form of colossal rockfalls and landslides that spread extensively across the adjacent plains. 

The journey of these landslides across the Martian terrain resulted in their compression and stretching, yielding the distinct wrinkles that now grace the images of Lycus Sulci, a crumpled feature found at the fringes of the aureole.

Over time, Lycus Sulci's prominence grew as Martian winds swept across its surface, eroding its material. The same winds carried fine sand and dust particles, dispersing them over nearby hills and ridges, leaving behind an indelible mark of their passage.

The magnitude of Olympus Mons's collapse is staggering. 

While singular landslides on Mars can measure hundreds of meters in thickness, Olympus Mons experienced multiple mammoth and overlapping collapses. 

This superposition of landslides makes Olympus Mons' landslides reach up to two kilometers in depth.

Martian volcanoes vs. Earth's

Despite their extraterrestrial setting, Mars's geological processes are similar to those witnessed on our planet. 

Although on a different scale, analog landslides have been observed around Earth's volcanic islands, such as Hawaii and the Canary Islands. As the new images reveal, Olympus Mons's grandeur extends beyond its towering form. 

Yelwa Crater's location, over 1000 kilometers from Olympus Mons's peak, serves as a testament to the astonishing distances these landslides traveled from the volcano's flanks before coming to rest.

As we continue to unravel the mysteries of our neighboring planets, Mars Express's exploration of Olympus Mons stands as a reminder of the intricate geological histories that lie hidden within the cosmos. 

Each image captured, each discovery made, brings us closer to understanding the turbulent and fascinating past of the Red Planet.