MADRID, 14 (EUROPA PRESS)
Images from the High Resolution Stereo Camera (HRSC) on ESA's Mars Express orbiter show the western part of the vast Acheron Fossae graben system on Mars.
The region in the camera's field of view is located about 1,200 kilometers north of Olympus Mons, the highest volcano in our Solar System. The crescent-shaped mountain range stretches for approximately 800 kilometers, merging with the Arcadia and Amazonian plains on its northern and western sides. To the south, the system meets the landslide mass at the foot of Olympus Mons' flanks.
Acheron Fossae is characterized by large, deep ruptures (faults) in the Martian surface. These linear fractures are a classic example of what geologists call a trench-and-plateau landscape: a pattern of uplifted and downturned crustal blocks running parallel to each other. These tectonic structures emanate from a planet's internal geological activity, where hot, malleable rock, or even molten magma from the planetary mantle (the thick layer of rock between the crust and the metallic core), rises to the surface. This process is also known as mantle convection, according to a statement from DLR, the German space agency that operates the HRSC.
Pressure from below stretches the surface, which in turn cracks along faults, causing blocks of crust to sink while neighboring uplifted blocks remain in place. Acheron Fossae likely formed approximately 3.7 to 3.9 billion years ago, during the Noachian Period, when Mars reached its peak geological activity. Over time, many of the depressions have been filled with various types of material, likely deposits carried by glaciers with their ice.
In the HRSC images, several deep depressions of varying depths run across the north-right side of the scene. Closer inspection reveals smooth material with a streamlined pattern at the bottom of these depressions. Known as linear valley fills (LVFs), these features are typically formed by the slow flow of debris embedded in glacial ice. The deposits are thought to be composed primarily of ice covered by a layer of debris, similar to block glaciers on Earth.
Deposits like these are often found in periglacial landscapes, which remain frozen almost year-round. This occurs on both Mars and Earth. Their presence suggests that the region experienced alternating cold and warm periods, driven by recurring cycles of freezing and thawing. These climatic fluctuations are due to changes in Mars' orbital parameters, particularly the changing tilt of its rotational axis.
Unlike the tilt of Earth's axis of rotation, which is relatively constant at about 23.5 degrees and has remained stable for billions of years thanks to our Moon, Mars' axial tilt fluctuates more sharply and frequently due to the gravitational influence of other planets.
These variations occur within a period of just five million years, making them frequent and relatively rapid. As a result, the amount of solar radiation received by Mars varies at different latitudes, causing changes in the Martian climate and redistributing ice on the surface. During periods of high inclination, the ice extends from the poles toward the mid-latitudes. When the inclination is lower, as is currently the case, the ice retreats toward the poles, but leaves traces that are still visible on the landscape.
