A study by INGV suggests that the particular morphology of the Martian gullies is due to the erosion caused by the action of liquid water which would emerge in the presence of favorable environmental conditions
Gullies on Mars, known as "gullies," may have originated from the action of liquid water. This is the hypothesis of the study result of the intuition of a researcher of the National Institute of Geophysics and Volcanology (INGV) and published in the magazine 'Italian Journal of Geosciences'.
On Earth gullies are deep furrows in the ground produced mostly by the flow of water over clayey rocks, with little vegetation cover and, therefore, little protection from runoff. They appear along the side of a mountain or a hill representing narrow and sharp courses of water. Also on Earth, the gullies are mainly exposed to the south (south in our hemisphere) because the erosive phenomenon on the clay is conditioned by exposure to the Sun. On the contrary, on Mars the "gullies" are mainly facing the poles, as if needed to maintain a low temperature, similar to terrestrial glaciers. This paradox may have a physical explanation
"The Martian gullies, discovered in 2000 thanks to the Mars Global Surveyor space probe on the escarpments of some regions of the red planet", explains Adriano Nardi, INGV researcher and author of the study, “they could be affected by seasonal spring phenomena influenced by the variability of external meteorological conditions; the water sources would be activated only in the presence of certain environmental, pressure and temperature conditions. In order to investigate this phenomenon we have proposed a new physical model called Weather-Springing Water (WSW)”.
The possibility that the gullies had been produced as a result of liquefaction of ice present in the subsoil (so-called permafrost) seemed impossible given the climatic conditions present on the red planet. However, over the last twenty years, several mutations in their morphology have been observed, as well as the appearance of new morphological structures.
"The geomorphological observations of the images and the numerical simulations of the atmospheric conditions", continues the researcher, “have indicated that the pressure and temperature present in the subsoil could favor the melting of the permafrost and in this way the outcrop phenomenon would take place where the aquifer meets a slope, but only when particular atmospheric conditions occur outside”.
Given the high instability of water on Mars, once it emerges on the surface it will tend to disappear rapidly. However, with the physical model devised by the INGV researchers, it turned out that the water, before evaporating, would have the necessary time to cross and erode these channels along the entire length of the observed morphologies.
"The simulations carried out have shown that the spring phenomenon occurs only sporadically", concludes Adriano Nardi. “It is a meteorological-geological event, capable of determining the particular morphological and geographical characteristics of the Martian gullies, otherwise difficult to explain. Research continues, also with a view to identifying potential sources of water to be used in the scenario of a future colonization of the planet”.
Nardi A. & Piersanti A. (2022) - "Geomorphologic observations and physical hypothesis on Martian gullies". Ital. J. Geosci., Vol. 141(2), 245-258.
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MARS | The presence of liquid water in the Martian badlands has been studied by means of a new physical model
An INGV study suggests that the particular morphology of the Martian gullies is due to erosion caused by the action of liquid water that would emerge in the presence of favorable environmental conditions
The badlands present on Mars, known as "gullies", could have originated from the action of liquid water. This is the hypothesis of the study ", the result of the intuition of a researcher from the National Institute of Geophysics and Volcanology (INGV) and published in the 'Italian Journal of Geosciences'.
On Earth, gullies are deep furrows in the ground produced mostly by the flow of water on clayey rocks, with scarce vegetation cover and, therefore, poorly protected from runoff. They occur along the side of a mountain or a hill representing narrow and sharp waterways. Also on Earth, the gullies are mainly exposed to the south (to the south in our hemisphere) because the erosive phenomenon on the clay is conditioned by exposure to the Sun. On the contrary, on Mars the "gullies" are mainly facing the poles , as if they needed to maintain a low temperature, similar to terrestrial glaciers. This paradox can have a physical explanation.
"The Martian gullies, discovered in 2000 thanks to the Mars Global Surveyor space probe on the slopes of some regions of the red planet", explains Adriano Nardi, researcher at INGV and author of the study, "could be affected by seasonal spring influenced phenomena by variable external weather conditions; the water sources would be activated only in the presence of certain environmental conditions, pressure and temperature. In order to investigate this phenomenon, we have proposed a new physical model called Weather-Springing Water (WSW)".
The possibility that the gullies were produced as a result of the liquefaction of ice present in the subsoil (so-called permafrost) seemed impossible given the climatic conditions present on the red planet. However, over the last twenty years, several mutations have been observed in their morphology, as well as the appearance of new morphological structures.
"The geomorphological observations of the images and the numerical simulations of atmospheric conditions", continues the researcher, "indicated that the pressure and temperature present in the subsoil could favor the melting of the permafrost and in this way the outcrop phenomenon would occur where the aquifer meets an escarpment, but only when particular atmospheric conditions occur outside”.
Water is quite unstable on Mars and once it reaches the surface it tends to disappear quickly. However, with the physical model conceived by INGV researchers, it was found that the water, before evaporating, would have enough time to flow and erode these channels for the whole length of the observed morphologies.
“The simulations carried out have shown that the phenomenon of spring occurs only sporadically”, concludes Adriano Nardi. “It is a meteorological-geological event, capable of determining the particular morphological and geographical characteristics of the Martian gullies, otherwise difficult to explain. Research continues, also with a view to identify potential water sources to be used in the scenario of a future colonization of the planet”.
Nardi A. & Piersanti A. (2022) - "Geomorphologic observations and physical hypothesis on Martian gullies". Ital. J. Geosci., Vol. 141(2), 245-258.
picture 1 – Reconstruction of the landscape of a Martian crater affected by gullies observed from the ground (satellite images observe the phenomenon from above). Image credits: NASA/JPL-Caltech/UArizona.
Image 1 - Reconstruction of the landscape of a Martian crater affected by gullies observed from the ground (satellite images observe the phenomenon from above). Image credit: NASA/JPL-Caltech/UArizona.
picture 2 - In diagrams (A) and (B) we see respectively the profile and the frontal view of the three morphological elements that characterize the Martian "gullies" (alcove, channel and apron) with an indication of the prevailing erosive or depositional phenomenon. The colored horizons delimit the narrow range of altitudes in which water can remain liquid on the surface according to the WSW model. Below water can exist only as vapor and above it only as ice, which can at most sublimate (i.e. pass directly from solid to vapor) if it is exposed to direct sunlight. In fact, according to this model, water can flow from the springs only seasonally and for a few hours a day, only while the slope is in the shade. In the image (C) a real example is compared with the scheme (B). Image: "ESP_011727_1490" by HiRISE (NASA/JPL/University of Arizona),
Image 2 - In diagrams (A) and (B) we see respectively the profile and the frontal view of the three morphological elements that characterize the Martian "gullies" (alcove, channel and apron) with the indication of the prevailing erosive or depositional phenomenon. The colored horizons delimit the narrow range of altitudes in which water can remain liquid on the surface according to the WSW model. Underneath, water can exist only as vapor and above only as ice, which can at most sublimate (that is, go directly from solid to vapor) if exposed to direct sunlight. According to this model, in fact, water can gush from the springs only seasonally and for a few hours a day, only while the slope is in the shade. In image (C) a real example is compared with the scheme (B). Image: "ESP_011727_1490" by HiRISE (NASA / JPL / University of Arizona),