This nearly circular formation is thought to have originated as an impact crater 4.1 to 3.7 billion years ago, during an era when Mars was heavily bombarded by asteroids and comets. Over eons, it has been reshaped by lava flows, glacial movement, and erosion from liquid water and wind, gradually doubling in size.
Channels etched into the crater's rim, some branching and some collapsed, suggest they were formed either by surface water flow or by subsurface water draining and undermining the overlying terrain. The grooved textures inside these channels point to past glaciation, where boulders embedded in glaciers scraped the surface as the ice advanced.
The crater walls also reveal "debris aprons"-smooth, rocky tongues left behind by glacier flow. These features formed when rock-laden ice slid down the crater walls during a period of glaciation, likely triggered by a past change in Mars's axial tilt.
Within the crater lies a chaotic mix of rock formations-knobs, mesas, channels, and flat plains-resembling a 'rocky road' dessert. The boulders likely represent erosion-resistant fragments of a once-central peak or the remnants of widespread regional processes. Some of the dark covering inside the crater is believed to be volcanic ash, while lighter patches contain clay minerals, hinting at long-gone pools of standing water.
Surrounding the crater are "wrinkle ridges," formed when cooling lava flows contracted and buckled the terrain. These and other features make Deuteronilus Cavus a compelling geological record of Mars's volcanic, hydrologic, and glacial activity over billions of years.
For over 20 years, ESA's Mars Express has revealed the Red Planet's diverse landscape in extraordinary detail, reshaping scientific perspectives on its history and evolution.