It is now almost universally accepted that liquid water once flowed on Mars, this belief supported by the discovery by the Mariner 9 mission  of numerous drainage channels whose form is consistent with formation by water (as opposed to lava channels, which have also been found in some areas). Fluvial processes can yield roughly symmetrical relief, such as the teardrop-shaped islands observed in many Martian stream beds. But in this case, fluvial processes can be ruled out as mechanisms for forming the D&M Pyramid as there are no indications that water ever flowed 1 km deep in Cydonia Mensae (1 km being the approximate height of the D&M Pyramid. It is also true that sharp edged multi-faceted symmetrical shapes are not characteristic of fluvial landforms.
As mentioned earlier, there is a theory that the basin north of Cydonia called Acidalia Planitia was once a shallow sea . There are features in the study area that are suggestive of lacustrine erosion, such as small craters with a "smudged" appearance that may at one time have been submerged and subject to shallow wave action. There are also some curvilinear features suggestive of lacustrine deposition. The D&M Pyramid, however, bears no resemblance to these features.
Aeolian depositional landforms on Mars typically take the form of sand dunes which are morphologically similar to those found on Earth, and have been described by Breed, Grolier, and McCauley . Dunes may occur singly, in small groups, or in dune fields, and are transient in form and location. Dunes will occasionally form star-shaped dunes and crescent-shaped symmetrical dunes known as barchans, but no dune will ever form a symmetrical polyhedron resembling the one under study. Flat sides and straight edges are unobserved in terrestrial or Martian sand dunes.
Aeolian erosion is now the dominant mechanism of geomorphic change on Mars and has been since the disappearance of liquid water and the cessation of volcanic activity, both of which have been estimated to have occurred early in the planet's history (>2 b.y. ago). One type of aeolian erosional feature found on Mars that can assume roughly pyramidal shapes are known as yardangs (Ward ). Yardangs are landforms that have been modified by deflation (removal of particles by wind) and by the abrasive action of wind-borne particulates, and typically resemble hills with sharp edges aligned with the prevailing winds. Their shape has been likened to upturned boat hulls. Yardangs can occasionally exhibit sharp edges, roughly flat sides, and bilateral symmetry. Comparison of the D&M Pyramid with landforms known to be yardangs immediately reveals some serious inconsistencies. The D&M Pyramid is an isolated landform with no other nearby objects exhibiting a similar shape and orientation. Yardangs normally begin with the downcutting and expansion of low spots, producing a series of parallel ridges that are gradually denuded into separate hills. These hills are eroded further by abrasion on the windward side and by deflation on the leeward side. It is rare for yardangs to be found in isolation.
Another type of aeolian landform that can be somewhat pyramidal in shape are known as ventifacts. Terrestrial ventifacts are normally formed from small rocks that are exposed to the abrasive action of sand carried by the wind. Multifaceted terrestrial ventifacts are believed to have been produced as a result of movement of a rock causing it to present different faces to the direction of the prevailing winds, a process described by Sharp  and Greeley and Iverson . Large ventifacts can also exist, produced from boulders and assuming a roughly pyramidal shape with three edges (dreikanters). These landforms present a long edge toward the prevailing winds, and a somewhat flat surface in the opposite direction. The leading edge is cut by abrasion of wind-borne particulates and the trailing surface apparently formed by deflation from locally reversed airflow, mechanisms essentially the same as those that form yardangs.
Five-sided symmetrical ventifacts or yardangs appear to be totally nonexistent on Earth and Mars. Prevailing winds are not likely to have shifted periodically with perfect symmetry and timing. Even if this seemingly impossible condition were satisfied, another factor would prevent such an object from forming. As noted above, locally reversed airflow can cut a flat surface perpendicular to the wind direction on the leeward side of a wind-cut hill. This locally reversed airflow, and associated surface level turbulence, would prevent the formation of this hypothetical five-sided ventifact. Each time the wind shifted to a new direction, the reversed airflow would start erasing the edges formed by other wind directions. The end result would not be a pyramidal hill, but rather a round one.
The overall morphology of the D&M Pyramid, with its straight edges and flat surfaces in radial arrangement, is inconsistent with the morphology of aeolian landforms. The nearby Face shows no evidence of wind faceting, and there are no intervening objects between the Face and the D&M Pyramid to deflect wind. Also inconsistent is the presence of a flat-faced protuberance at the front of the object, a flat surface that should not exist at the leading edge of wind cut features such as yardangs or ventifacts. It is reasonable to conclude that aeolian processes cannot have produced the D&M Pyramid due to the lack of a plausible mechanism of formation, and the absence of similar landforms on Mars or Earth.
The results of downslope movement of large amounts of rock and/or soil under the influence of gravity has been observed in many areas of Mars. This process, perhaps driven by the freezing and thawing of subsurface water, was likely a factor in shaping many of the irregular knobs found in Cydonia Mensae, as well as the angular remnants of cratered plateau material to the south. Mass wasting, however, is unlikely to have formed the D&M Pyramid. It is uncharacteristic of mass wasting of loose material, or slumping of single masses, for such material to slide off of a hill in such a way as to leave behind multiple flat surfaces and straight edges where none had previously existed.
It is also unlikely that such mass wasting would occur symmetrically. When mass wasting produces a flat surface, it is normally due to some previously existing fault or sedimentation layer that provides a shear surface for the mass wasting or slumping. An analogous example from Earth geology would be the failure of a slope consisting of Cretaceous clay that has such internal layers. If this type of internal layering occurs on Mars, it is unlikely to occur symmetrically so as to yield a symmetrical erosional remnant.
Volcanism on Mars was once an important factor in producing and modifying surface features. Most volcanism appears to have ceased ~2 b.y. ago, and is described by Carr  as having been concentrated in certain regions; the Tharsis bulge, and the Elysium and Hellas regions being the most prominent. There are no signs of significant volcanic activity in the Cydonia Mensae region, thus drastically reducing the possibility of an y landform in the region being thus formed.
Fluvial erosion of terrestrial volcanoes can produce erosional calderas that are roughly symmetrical, but these landforms do not even faintly resemble the object under study. Erosional calderas form from the downcutting and widening of channels that eventually merge to form amphitheatre-like depressions in the sides of the volcano. These depressions extend for most of the height of the volcano, and are roughly parabolic in cross section, never flat. No Martian volcanoes observed to date show signs of having been heavily denuded by rainfall, due to the apparent lack of large amounts of rainfall in recent epochs. Additionally, the D&M Pyramid has no vent at its apex, and exhibits a symmetry unknown in volcanic landforms.
Nearly all examples of naturally occurring symmetrical polyhedra are the result of crystal growth. It has been theorized that a freeze-thaw cycle might have produced unusual crystal growth from the water believed by some to lie beneath the surface of Mars, but the D&M Pyramid could not possibly have been produced in this manner. The size of the object (> 2 km long) would alone preclude the possibility of it being an ice crystal, as would the fact that ice crystals have hexagonal symmetry. Crystallization of other substances can also be ruled out as it is impossible for any normal crystal to possess 5-fold symmetry. The D&M Pyramid actually deviates from perfect 5-fold symmetry by being somewhat elongated along one axis, and is thus even further removed from crystalline geometries.
There is an exotic form of "crystalline" matter known as quasicrystals. These exhibit icosahedral symmetry in three dimensions, and thus have five-fold symmetry planes in two dimensional sections. Quasicrystals are produced by rapid quenching of molten alloys of aluminum and magnesium. The materials and process of formation do not remotely resemble the conditions and surface chemistry of Mars, and can also be ruled out as a causative mechanism for five-fold landforms.
The Geomorphic Hypothesis is thus left with no mechanism that can explain the formation of the D&M Pyramid. This object's 5-sided shape and bilateral symmetry is unlike any landform seen to date in this solar system, and even small-scale phenomena such as crystal growth cannot explain its morphology.