Mars is a world marked by dramatic landscapes and few regions showcase this better than Acheron Fossae, a spectacular network of deep cracks and valleys that slice through the red planet’s surface like ancient scars. Recent images from the European Space Agency’s Mars Express spacecraft reveal the western edge of this fascinating geological formation, offering new insights into Mars’s violent past and changing climate.
Image of Mars captured by the Hubble Space Telescope between April 27 and May 6, 1999, when Mars was 87 million kilometres from Earth (Credit : NASA/ESA)
Acheron Fossae is an extensive system of deep, fault like cracks (known as fossae), with alternating chunks of raised and lowered ground, a pattern geologists call “horst and graben.” Picture a broken chocolate bar where some pieces have been pushed up while others have dropped down, creating a jagged landscape of ridges and valleys that can be hundreds of kilometers long and several kilometers deep.
These features weren’t created overnight. Likely dating back over 3.7 billion years to when Mars was most geologically active, such a pattern was created as hot material rose upwards beneath the martian crust. As molten rock pushed upward from deep within Mars, it stretched and cracked the planet’s surface creating the deep valleys we see today.
Image of Acheron Fossae in Tharsis region on Mars (Credit : NASA)
What makes Acheron Fossae particularly intriguing isn’t just how it formed, but how it continues to change. The valley floors are relatively smooth, marked by gently weaving lines reminiscent of a flowing river. Rather than water, these valleys have been filled by a slow, viscous flow of ice rich rock, a lot like the rock glaciers we see here on Earth.
These Martian rock glaciers act like geological time capsules, preserving evidence of the Martian climatic history. Rock glaciers are very sensitive to changes in climate, and so act as good markers for how a planet’s environment has changed over time. Here, they indicate that this region of Mars has experienced alternating periods of cool and warm, freeze and thaw.
The key to understanding these climate swings lies in Mars’s unstable tilt. Unlike Earth, which maintains a relatively steady tilt thanks to the Moon’s stabilising influence, Mars wobbles dramatically over time. Mars’s tilt has swung between 15 and 45 degrees in the last 10 million years, while Earth’s has varied between 22 and 24.5 degrees.
These variations, known as the Milankovitch cycles, create alternating ice ages and warm periods on Mars. During extreme tilts, ice can creep near to the planet’s equator before shrinking back to its poles during warmer periods.
The images also reveal how erosion has transformed the landscape over millions of years. To the right of the main fossae, the deep cracks transition into flat, dark lowland plains, with a strip of raised mounds and rocky hills in between. These are the remains of what was once a continuous rock layer that has been slowly worn away by flows of ice and rock over time, leaving behind rounded hills called knobs and flat topped plateaus called mesas.
This erosion process creates a distinctive transition visible in the topographical data, from the deep red and yellow tones of higher ground gradually melting into light and darker blues indicating lower elevations. It’s like watching a mountain range slowly dissolve into a plain over geological time.
Illustration of ESA’s Mars Express spacecraft (Credit : NASA/JPL)
These remarkable insights come courtesy of ESA’s Mars Express spacecraft, which has been capturing and exploring Mars’s landscapes since 2003. Using its High Resolution Stereo Camera, the orbiter has mapped the planet’s surface in unprecedented detail, colour, and three dimensions for over two decades.
As we continue studying Mars, features like Acheron Fossae serve as natural laboratories for understanding planetary geology and climate evolution. They remind us that planets are dynamic systems, constantly changing over geological time scales. For future Mars missions, both robotic and human, understanding these processes will be crucial for navigation, resource utilisation, and safe exploration of our planetary neighbour.
Source : When Martian Ground Falls Apart