Winds on Mars as a “cosmic sandblaster”: Mars Express captured grooves and ridges formed by sand erosion
Powerful, sand-laden winds on Mars do not shape only dunes and dusty veils in the atmosphere—they literally grind rocks. The European Space Agency (ESA) and partner institutions processing data from the Mars Express orbiter have released scenes that clearly show how grains of sand, lifted into the thin atmosphere, become a natural “tool” for working the terrain. Once the sand gets moving, it strikes the ground, enters existing cracks, and over time carves long, neatly oriented grooves into sedimentary layers. What reads in the image as a series of tidy lines is in fact the result of long-term, slow erosion that relentlessly “pulls out” the softer parts of the terrain.
At the heart of the story are so-called
yardangs—elongated ridges, mounds, or pillars that remain “standing” when the surrounding material is abraded and carried away. Such structures are not rare on Mars: the planet has no stable surface water flows like Earth, no vegetation, and the ground is widely exposed to atmospheric processes. Because of this, over vast spans of time, wind becomes one of the most persistent forces reshaping the landscape.
Yardangs are, put simply, a negative image of erosion: what we see as a ridge is what survived, while everything around it was gradually removed. When sand is lifted high enough and remains in motion long enough, it acts like “sandblasting” in a natural laboratory—and Mars, without rain and vegetation, is the ideal stage for such a process.
The ridges are “signed” by the prevailing wind direction
In views from the Eumenides Dorsum area, within the vast Medusae Fossae Formation,
yardangs are tilted and aligned in the same direction, and in some depictions they gently curve as they enter from the southeast. Such consistent orientation is no coincidence, but a geological record of prevailing winds over a longer period: a wind that persistently blows from a similar direction intensifies abrasion on one side of a ridge and gradually elongates it. When the same process repeats for thousands or millions of years, the result is fields of parallel grooves that can stretch for tens of kilometres. In soft, sedimentary layers, wind most easily “finds” existing weaknesses, such as cracks or faults, and widens them as the surrounding terrain thins and disappears. The consequence is a landscape that looks almost designed, even though it was formed exclusively by natural forces.
According to the scene description, the
yardangs field is located on the northern edge of the Eumenides Dorsum mountain range, while the massif extends farther west beyond the frame.
In descriptions of this location, ESA states that Eumenides Dorsum lies west of the volcanic Tharsis region and belongs to the Medusae Fossae area, near Mars’s equator. Views produced by the HRSC camera cover thousands of square kilometres and offer resolution on the order of tens of metres per pixel, which is enough to distinguish individual ridges, gullies, and transitions between material types. At such transitions, where softer sedimentary deposits abut more resistant layers (often interpreted as volcanic material), wind has the “material” to build strongly contrasting shapes. On one side, deeply incised grooves and stripped channels form, and on the other, elongated, harder “bones” of the relief remain, defining the visual signature of the entire area.
Medusae Fossae: a vast dusty formation with open questions
The Medusae Fossae Formation (MFF) is one of the largest and most enigmatic formations along Mars’s equator. According to analyses published by the German DLR and partners, the MFF stretches more than 5,000 kilometres between volcanic centres around Tharsis and Elysium, along the boundary between Mars’s highlands and lowlands, and its total area is comparable to the size of India. Available interpretations emphasise that this is material that erodes easily, which explains why wind here can build massive complexes of
yardangs, channels, and “gnawed” plateaus. The MFF is also often described as one of the key sources of dust on Mars, further linking the geology of the terrain with the atmosphere and climate. In other words, this is not just a “landscape”, but a system that produces and transports material—and is then remodelled again by that same material.
The origin of the MFF is still debated, but some expert interpretations connect it with volcanic pyroclastic deposits—a mixture of ash and rock fragments laid down by powerful eruptions in the distant past. DLR notes that such deposits could be linked to eruptions from the broader Tharsis region or Olympus Mons, several billion years ago, after which winds for centuries and millennia continued to “fine-tune” the relief. On the other hand, in newer analyses of the MFF subsurface based on radar data from the MARSIS instrument, ESA raised an additional question about composition: according to those results, parts of the deposits could contain significant amounts of ice in layers below the surface. Such a conclusion, if further confirmed, changes the perspective on the MFF: the region would simultaneously be a vast dust reservoir and potentially a large store of water in a “locked” state. That is precisely why Eumenides Dorsum and the wider Medusae Fossae area remain among the locations regarded as a priority for understanding Mars’s history.
Three processes in one place: impact, lava, and wind
A particularly interesting element of the views from this area is the meeting of multiple processes within a relatively small space. Alongside the
yardangs fields, an impact crater is visible that, based on the preserved rim and surrounding structures, looks relatively “fresh” in geological terms. Around the crater, a broad, lobed “blanket” of ejected material—
ejecta—can be distinguished, formed at the moment of impact, when material from the impact site was thrown outward and then settled around the crater. That very rim, with irregular contours, indicates that the ejected material did not fall like “dust”, but behaved dynamically, spreading across the surrounding terrain. For geologists, this matters because such a pattern can carry information about the properties of the substrate at the time of impact, including the proportion of dust or ice.
Ejecta can also have a “secondary” role in shaping terrain. NASA/JPL explains in descriptions of related structures that ejected material sometimes acts as a protective armour that slows erosion beneath it, so part of the terrain remains elevated relative to its surroundings. Such examples help us understand how wind on Mars selectively removes soft layers, while “protected” parts retain their shape longer. In regions where aeolian erosion and craters overlap, geologists gain additional “markers” for reading relative ages: what is covered and preserved can keep its shape longer, while unprotected parts “wear down” faster. In the case of Eumenides Dorsum, the crater and its blanket of material act as a natural “time stamp” in a landscape that is constantly changing.
The third element in this local puzzle is the so-called
platy flow—a “plate-like flow” that in satellite images can resemble floating slabs of ice. The mechanism often described for such surfaces starts with lava movement: the surface layer cools and hardens into a crust while lava below continues to flow. As the mass underneath moves, the solid crust is stretched, breaks into large plates, and those plates can shift, rotate, and “stack”, creating the impression of rafts or slabs that slid across the substrate. Studies dealing with
platy surfaces on Mars note that interpretations have historically varied—from lava to ice to “muddy” flows—but a key characteristic repeatedly appears: large plates separated by edges and depressions. In the context of the Eumenides Dorsum scenes, such terrain suggests that active flows of viscous material occurred here in the past, and later processes then covered it, cut into it, or exposed it again.
The sequence of layers and traces of time
When
platy surfaces and
yardangs are seen at the same location, a key question arises: which came first? If
yardangs cut across a plate-like flow, or it clearly appears that they developed on top of its surface, that suggests wind-driven erosion took place after the lava cooled and stabilised. In other words,
platy flow would be older in that local chronology, and
yardangs younger—a product of a later phase, when sand and dust again “caught” the soft sedimentary layers and began to abrade them. Such a conclusion matters because Mars often requires reading time through relationships between forms: without “field” sampling on site, the geological story is assembled from what covers, cuts, or deforms something else. In that methodology, every edge, every boundary, and every “overlap” gains the weight of evidence.
That is why the Eumenides Dorsum scenes are not only visually attractive but also analytically useful. In a single scene it is possible to trace at least three geological “episodes”: deposits that provided a soft substrate for aeolian erosion, then a volcanic event that left a plate-like flow, and an impact that created a crater and an
ejecta blanket. After that comes a long phase of wind, which rearranges everything left on the surface again and again. Such multi-layering of processes helps in a broader understanding of the MFF: the region is not only “desert-like”, but simultaneously an archive of volcanism, impacts, and atmospheric processes. And when a crater, flows, and
yardangs “meet” in one place, you get a rare, clear cross-section of events that on Mars otherwise disperse across space and time.
Dust as a climatic and operational factor
Mars’s atmosphere is thin compared to Earth’s, but it can be extremely dynamic. In newer analyses tracking
dust devils—whirling columns of dust—ESA highlighted that strong near-surface winds are widespread and that these vortices play an important role in lifting dust from the surface. The dust then affects visibility, temperature, and the atmosphere’s energy balance, and in extreme cases it can also contribute to the development of regional or global dust storms. For robotic missions, dust is also an operational problem: it can cover instruments, reduce the efficiency of solar panels, and complicate optical measurements, and changes in atmospheric transparency affect observation planning. In that sense, wind-made reliefs such as
yardangs become indirect “indicators” of where the wind most often “feeds” on material.
That is why
yardangs and related aeolian structures are not just a geological curiosity, but an indicator of where the wind is most active, where sand is lifted most easily, and in which directions it moves over the long term. When planning future landings, choosing locations, and setting equipment operating modes, understanding Mars’s “dust economy” becomes just as important as selecting a geologically interesting target. In that context, long-running missions like Mars Express have special value: they provide a continuous observational framework, comparable across years and decades, so patterns can be analysed without relying on isolated “luckily caught” moments. Long-term data, combined with newer missions from other agencies, build a picture of Mars as a planet where wind is not a side phenomenon but a lasting force that defines both the landscape and the atmosphere.
Mars Express and HRSC: a 3D map of the planet that is still being expanded
A key role in these views belongs to the orbiter instruments, above all the High Resolution Stereo Camera (HRSC), developed at DLR. According to mission data, HRSC has been mapping Mars since 2004 at high resolution, in colour and in 3D, enabling the creation of digital terrain models and perspective views. Such stereoscopy is not just a visual add-on: it helps distinguish ridges and depressions, measure slopes, estimate heights, and spot details such as crater rims or “plates” on
platy terrains. DLR stresses that the continuity of mapping is crucial for understanding the global picture of Mars, because a single consistent dataset allows comparisons across different regions and different process types. When those terrain models are combined with geologists’ interpretations, you get a surface “narrative” that goes beyond a single photograph.
According to DLR and ESA, Mars Express was launched on 2 June 2003 and, scientifically, represents one of Europe’s longest-running missions in orbit around another planet. CNES states in its project data that the mission’s operational life has been extended until the end of 2026, meaning new data on the atmosphere, surface, and subsurface are still being collected. In combination with the MARSIS radar, which has also been used to estimate the structure of deposits in the Medusae Fossae Formation, an ever more complete picture of the region emerges: from surface erosion and
yardang orientation to layers hidden kilometres below. Every new mosaic, every relief detail, and every measurable “irregularity” becomes additional pieces of the puzzle of how Mars, from a once-active planet with volcanism and a variable climate, became today’s world of dust, wind, and slow but relentless processes.
Sources:- ESA – “Yardangs on Mars”: explanation of the erosion mechanism by wind-borne sand and the context of the HRSC image ( link )
- ESA Multimedia – “Euminedes Dorsum”: the Eumenides Dorsum location, resolution, and area coverage in HRSC images ( link )
- DLR – “Blown by the wind: The Medusae Fossae Formation on Mars”: the scale of the MFF, the position of Eumenides Dorsum, hypotheses on the origin of the deposits, and examples of yardangs ( link )
- NASA Science Photojournal – “Medusae Fossae Yardangs”: description of the formation and the creation of yardangs by wind-borne sand ( link )
- ESA – “Dancing dust devils trace raging winds on Mars”: catalogue of dust vortices and conclusions about near-surface winds ( link )
- ESA – “Buried water ice at Mars's equator?”: MARSIS radar analysis and discussion of the composition of deposits in the MFF ( link )
- DLR – “Mars Express”: data on the HRSC camera and long-term mapping of Mars in colour and 3D ( link )
- NASA/JPL – “Pedestal Crater and Yardangs”: background on the role of ejecta deposits and wind-driven erosion in preserving relief ( link )
- Lunar and Planetary Science Conference (2007) – Sakimoto, Gregg, Fagan: paper on “platy” surfaces and the debate on possible origins (lava/ice/mud) ( link )
- CNES – “Mars Express” (project page): basic mission data and extension of operations ( link )
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