The common surface features of Mars include dark slope streaks, dust devil tracks, sand dunes, Medusae Fossae Formation, fretted terrain, layers, gullies, glaciers, scalloped topography, chaos terrain, possible ancient rivers, pedestal craters, brain terrain, and ring mold craters.
Ancient shoreline evidence Recent studies, particularly from China’s Zhurong rover and supporting orbital data, provide robust evidence for ancient shorelines in Mars’ northern lowlands, notably in Utopia Planitia. Ground-penetrating radar profiles collected along a 0.8 km traverse detected 76 subsurface reflectors dipping uniformly between 6° and 20° (mean ≈ 15°) at depths of 9–35 m, closely matching the foreset bedding angles of terrestrial sandy beaches.
Sediment-texture analysis indicates these layers consist of sand-sized particles delivered by rivers from the southern highlands and reworked by gentle wave action rather than by wind or lava flow.
Crater-count dating and stratigraphic correlations bracket the northern ocean transgression to ≈ 3.68 Ga, with regression and surface-water loss complete by ≈ 3.42 Ga, implying a 200–300 Myr interval of stable coastal conditions during the Late Noachian–Early Hesperian epochs.
Analogs on Earth show beach face slopes of 4°–26° under wave-dominated conditions, matching the Martian dip angles and strengthening the interpretation of a coastal depositional environment on early Mars.
These findings are complemented by orbital observations of > 15 000 clay-rich mounds in nearby Chryse Planitia—remnants of ancient highlands eroded by water nearly 4 billion years ago—preserving layered, phyllosilicate-bearing outcrops that record prolonged aqueous alteration and shore-zone retreat.
Collectively, the stratigraphy, sedimentology, and chronology of these coastal deposits establish the strongest quantitative case yet for dynamic, wave-influenced Martian beaches and a long-lived northern ocean. Such environments may have been prime habitats for early microbial life, making them high-priority targets for future astrobiological exploration.
Slope streaks
A new phenomenon known as slope streaks has been uncovered by the HiRISE camera on the Mars Reconnaissance Orbiter. These features appear on crater walls and other slopes, and they are thin and many hundreds of metres long. The streaks have been observed to grow slowly over the course of a year or so, always beginning at a point source. Newly formed streaks are dark in colour but fade as they age until white. The cause is unknown, but theories range from dry dust avalanches (the favoured theory) to brine seepage.
Examples of dark slope streaks from various parts of Mars are shown below. Click on image to get a better view.
Recurrent slope lineae
Recurrent slope lineae are small dark streaks on slopes that elongate in warm seasons. They may be evidence of liquid water.
Dust devil tracks Many areas on Mars experience the passage of giant dust devils. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil travels by, it blows away the coating and exposes the underlying dark surface. These dust devils have been seen both from the ground and from orbit. They have even blown the dust off the solar panels of the Spirit and Opportunity rovers on Mars, greatly extending their lives. The twin Rovers were designed to last for 3 months; instead, Spirit lasted for 6 years, 77 days, while Opportunity continued to operate for 14 years, 136 days. The pattern of the tracks have been shown to change every few months.
Layers
Many places on Mars show rocks arranged in layers. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers. On the Earth much layering of rocks is done by sediments that were deposited on the floors of lakes. A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.Grotzinger, J. and R. Milliken (eds.). 2012. Sedimentary Geology of Mars. SEPM. Layers can be hardened by the action of groundwater. Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through. When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents. Consequently, layers of dust could not later easily erode away since they were cemented together.
Layers in Ice Cap
Sand dunes Many locations on Mars have sand dunes. An erg (or sand sea), made up of aeolian dune fields referred to as the Circumpolar Dune Field surrounds most of the north polar cap. The dunes are covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring. Many martian dunes strongly resemble terrestrial dunes but images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter have shown that Martian dunes in the north polar region are subject to modification via grainflow triggered by seasonal sublimation, a process not seen on Earth. Many dunes are black because they are derived from the dark volcanic rock basalt. Extraterrestrial sand seas such as those found on Mars are referred to as "undae" from the Latin for waves.
Gullies
Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars. They are named for their resemblance to terrestrial gullies. First discovered on images from Mars Global Surveyor, they occur on steep slopes, especially on the walls of craters. Usually, each gully has a dendritic alcove at its head, a fan-shaped apron at its base, and a single thread of incised channel linking the two, giving the whole gully an hourglass shape. They are believed to be relatively young because they have few, if any craters.
On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers believed that the processes carving the gullies involve liquid water. However, this remains a topic of active research.
Gullies on Dunes Gullies are found on some dunes. These are somewhat different from gullies in other places, like the walls of craters. Gullies on dunes seem to keep the same width for a long distance and often just end with a pit, instead of an apron. They are often just a few meters across with raised banks along the sides.Dundas, C., et al. 2012. Seasonal activity and morphological changes in martian gullies. Icarus: 220, 124–143. Many of these gullies are found on dunes in Russell (Martian crater). In the winter dry ice accumulates on the dunes and then in the spring dark spots appear and dark-toned streaks grow downhill. After the dry ice is gone, new channels are visible. These gullies may be caused by blocks of dry ice moving down the steep slope or perhaps from dry ice starts the sand moving.McEwen, A., et al. 2017. Mars The Pristine Beauty of the Red Planet. University of Arizona Press. Tucson. In the thin atmosphere of mars, dry ice will expel carbon dioxide with vigor.
Medusae Fossae Formation
The Medusae Fossae Formation is a soft, easily eroded deposit that extends for nearly 1,000 km along the equator of Mars. Sometimes the formation appears as a smooth and gently undulating surface; however, in places it is wind-sculpted into ridges and grooves. Radar imaging has suggested that the region may contain either extremely porous rock (for example volcanic ash) or deep layers of glacier-like ice deposits amounting to about the same quantity as is stored in Mars' south polar cap.
The lower portion (member) of Medusae Fossae Formation contains many patterns and shapes that are thought to be the remains of streams. It is believed that streams formed valleys that were filled and became resistant to erosion by cementation of minerals or by the gathering of a coarse covering layer. These inverted stream beds are sometimes called sinuous ridges or raised curvilinear features. They may be a kilometer or so in length. Their height ranges from a meter to greater than 10 meters, while the width of the narrow ones is less than 10 meters.
The wind has eroded the surface of the formation into a series of linear ridges called yardangs. These ridges generally point in the direction of the prevailing winds that carved them and demonstrate the erosive power of Martian winds. The easily eroded nature of the Medusae Fossae Formation suggests that it is composed of weakly cemented particles, and was most likely formed by the deposition of wind-blown dust or volcanic ash. Layers are seen in parts of the formation. A resistant caprock on the top of yardangs has been observed in Viking, Mars Global Surveyor, and HiRISE photos. Very few impact craters are visible throughout the area so the surface is relatively young.
Yardangs
Yardangs are common in some regions on Mars, especially in the Medusae Fossae Formation of the Amazonis quadrangle and near the equator. They are formed by the action of wind on sand sized particles; hence they often point in the direction that the winds were blowing when they were formed. Because they exhibit very few impact craters they are believed to be relatively young.
Fretted terrain
Fretted terrain is a type of surface feature common to certain areas of Mars and discovered in Mariner 9 images. It lies between two different surfaces. The surface of Mars can be divided into two parts: low, young, uncratered plains that cover most of the northern hemisphere, and high-standing, old, heavily cratered areas that cover the southern hemisphere and a small part of the northern hemisphere. Between these two zones is the fretted terrain, containing a complicated mix of cliffs, mesas, buttes, and straight-walled and sinuous canyons. Fretted terrain contains smooth, flat lowlands along with steep cliffs. The scarps or cliffs are usually 1 to 2 km high. Channels in the area have wide, flat floors and steep walls. Fretted terrain is most common in northern Arabia, between latitudes 30°N and 50°N and longitudes 270°W and 360°W. Parts of the fretted terrain are called Deuteronilus Mensae and Protonilus Mensae.
In fretted terrain, the land seems to transition from narrow straight valleys to isolated mesas. Most of the mesas are surrounded by forms that have been called a variety of names (circum-mesa aprons, debris aprons, rock glaciers, and lobate debris aprons). At first they appeared to resemble rock glaciers on Earth, but scientists could not be sure. Eventually, proof of their true nature was discovered by radar studies with the Mars Reconnaissance Orbiter and showed that they contain pure water ice covered with a thin layer of rocks that insulated the ice.
In addition to rock covered glaciers around mesas, the region has many steep-walled valleys with lineations—ridges and grooves—on their floors. The material comprising these valley floors is called lineated valley fill. In some of the best images taken by the Viking Orbiters, some of the valley fill appeared to resemble alpine glaciers on Earth. Given this similarity, some scientists assumed that the lineations on these valley floors might have formed by flow of ice in (and perhaps through) these canyons and valleys. Today, it is generally agreed that glacial flow caused the lineations.
Glaciers
Glaciers, loosely defined as patches of currently or recently flowing ice, are thought to be present across large but restricted areas of the modern Martian surface, and are inferred to have been more widely distributed at times in the past."The Surface of Mars" Series: Cambridge Planetary Science (No. 6) Michael H. Carr, United States Geological Survey, Menlo Park