The High Resolution Stereo Camera on ESA’s Mars Express orbiter has captured stunning images of Moreux crater, a huge impact crater in the Terra Sabaea region of the Red Planet.
This image of Moreux crater comprises data gathered on October 30, 2019. Image credit: ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO.
When compared to other impact craters on both Mars and Earth, Moreux crater appears a little misshapen and messy — the result of ongoing erosion over Martian history.
The crater is roughly 3 km deep, and spans 135 km from edge to edge.
Its central peak, created as material from the crater floor rebounded and rose upwards following the initial impact, is around 2 km in height.
Its egg-shaped rim is broken up, its dark walls are ridged, rippled and mottled.
Perspective view of the Moreux crater. Image credit: ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO.
The range of colors featured in the new images from Mars Express reveals much about the composition of a particular region, material or feature.
While the surrounding material is visible in hues of butterscotch and caramel, the crater’s walls are dark, resembling a smudged ring of ash or charcoal.
Dark brown and black dunes cover the crater floor, while the peak remains a pale yellow-orange.
Dark, prominent ejecta, comprising material flung outwards during the crater-forming collision, spread outwards from the crater rim, discoloring and encroaching upon the lighter surrounding terrain.
This varied color palette reflects an equally varied geological composition.
The dunes within and around the crater are thought to contain sandy material rich in pyroxene and olivine: rock-forming minerals that are mafic (containing magnesium and iron) and characterized by their typically dark appearance.
Perspective view of the Moreux crater. Image credit: ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO.
Martian winds are also thought to have swept and gathered fine, basaltic, volcanic sand and ash into and around the crater.
Basaltic rock is commonplace on both Mars and other celestial bodies. It is a key component of the maria, or seas, on the Moon, for instance, and causes them to appear visibly and notably darker than the lunar highlands.
Many of the features, such as dunes and flows, surrounding the central peak and southern region of Moreux crater (to the left of the first image) appear to have been formed by ice.
This is thought to have occurred in the form of substantial episodes of glacial activity over the past few million years.
Many other features show signs of wind erosion, or having been formed via wind-related processes — most notably, the dunes covering the crater floor.
These dunes are largely sickle-shaped (barchanoid), and reveal much about wind direction within and across the crater.
From the orientation of the dunes, scientists inferred a complex system of prevailing winds, likely influenced by the topography of the crater itself.
Dunes to the north and east of the central peak are largely influenced by winds coming from the northeast, while dunes sitting west of the park are controlled by winds from the northwest.
These cross-cutting winds create an interesting and unique dune morphology within Moreux crater, adding to the feature’s intrigue.
