Martian sands in motion

They have a height between 1 and 2 meters, their extension can oscillate from 5 meters up to 40 and have risen to the fore for a study that has investigated their movements: it is sandy structures rather widespread on Mars, defined megaripple or transverse Aeolian crests (Tar, Transverse Aeolian Ridge).

The research, published on Journal of Geophysical Research: Planets (item: “Widespread Megaripple Activity Across the North Polar Ergs of Mars”), was coordinated by Planetary Science Institute of Lakewood (United States) and was carried out by an international team, which also saw the participation ofNational Institute of Astrophysics.

The ridges at the center of the survey, also found on the Earth’s surface, I’m a geological structure modeled bywind action it is characterized by intermediate sizes compared to the more contained ripples (ripple) and at dunes which can reach hundreds of meters in height and extension. The megaripple, the subject of numerous studies, are generally believed inactive and therefore fossils of the ancient climate of Mars. However, there are exceptions: the authors of the essay found that one large ‘population’ of such crests, located in the northern polar regions of the planet, you are moving together with the dunes and the ripple.

The research team drew on the images made by Hirise camera, instrument installed on the probe Mars Reconnaissance Orbiter from the NASA, during a rather long period (six Martian years, equal to 13 of the Earth). From the analysis of the data, the scholars have noticed that the sands north pole of Mars are on the move: le megaripple feature a migration rate average of 0.13 meters for each Earth year, while the ripple close to them they move on average by 9.6 meters per year, during only 22 days of the northern summer. This high figure, according to scientists, would explain the dynamism from the megaripple.

The researchers found that the thin Martian atmosphere can move the coarse-grained sand of these crests and the mapping of the vases fields of dunes of the extreme northern regions of Mars pointed out that these formations are not as static as previously believed. The migrations of these structures shaped by the wind are connected to seasonal variations: the long one polar winter puts a brake on movement, while the currents that blow in the late spring and in summer they restart the phenomenon, the rate of which also compensates for periods of inactivity.

The megaripple polar regions move relatively quickly higher than those located at lower latitudes. The particular intensity of their dynamism is probably related to greater streams of sand identified in the nearby dunes and moved by seasonal winds in the period in which the polar ice is in the phase of sublimation. This phenomenon – conclude the authors of the paper – suggests that a good part of the surface of the Red Planet be geologically active.

Above: the sandy structures of the north pole of Mars as seen by Hirise (Credits: Nasa / Jpl / University of Arizona).

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