Traces of Tectonic Events Recorded in the Martian Sediment of Valles Marineris

How to study the geological history of Mars? On Earth, this question does not really represent a problem because the continuous deposition of sediment makes it possible to record a large proportion of deformation episodes. The sedimentary rocks thus represent a formidable collection of the tectonic history of our planet. But Mars is far from experiencing the same conditions as Earth in terms of sedimentation. Yet researchers have found traces of tectonic events in sedimentary deposits on the Red Planet. And their results suggest that the giant Mars valley, Valles Marineris, may have been formed by progressive subsidence along the larger common faults.

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[EN VIDÉO] Casey Valles, The Wonderful Valley of Mars
Created with 3D images obtained by the Mars Express probe, this video takes us over the Martian valley Casey Wallace. More than about 3,000 km, its relief includes a vast and, of course, a large number of channels during very old floods.

Mars certainly never had tectonic plates compared to Earth. As a result, basins formed by tectonic processes are rare and their evolutionary history is generally poorly constrained. On Earth, one way to study the tectonic history of a place is to look at the deformation recorded in it. sedimentary deposit.

sediment required to record tectonic history

vertical movements of the ground, and especially episodes of subtraction (of sediments, forming valleys) generally well stored as follows: under the influence of erosion of reliefs, sediment Deposited in low topographical areas. Source, morphology And the superposition of these sedimentary deposits can then be used to reconstruct fault movement and the tectonic evolution of the basin. The same strategy can be applied to Mars as well.

Alluvial sedimentary cones are actually quite abundant on the Red Planet’s surface, even though most are thought to have followed a period of the planet’s river activity. that happened 3.7 billion years ago. Rather, sedimentary deposits were observed on Mars that formed during the dry period that followed. so it is not sediment carried by water liquid Rather than large-scale flows, such as landslides or “debris-flows”, even though some deposits are associated with rare humid climate episodes.

Valles Marineris. sedimentary deposits in

Most of these sedimentary deposits are found at the edges of impact craters and are therefore not associated with tectonic movements, which is very different from the situation on Earth where almost all sedimentary valleys associated with tectonic processes. Mars, however, presents a vast geological formation known as the Valles Marineris: a vast network of canyons that intersect at depths of several kilometers. crust Of the planet However, the reliefs created by these basins are favorable for the formation of alluvial sedimentary cones. Scientists are interested in the fact that these sediments could have been deposited in the context of active tectonics and used to reconstruct the tectonic evolution of Veles Marineris.

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A team of researchers from the Department of Earth Sciences (Museum of Natural History) in London studied the morphology of these sedimentary deposits using instruments carried by the probe. Mars Reconnaissance Orbiter (MRO). The valley floor is actually covered with sedimentary cones whose supply channels cut the slopes from the edge of the plateau. The morphology of these deposits is well matched with that of the suburban alluvial deposits. mass flow and debris flow. Some deposits also suggest the presence of environmental of lake At the bottom of the valley, but only in places. The overall finding suggests that cones sometimes form intermittently with traces of fluvial processes.

Scientists have also noted the presence of “raised” sedimentary deposits up to 4 km above the valley floor. They terraces The sediments, which are well known on Earth, have been interpreted as ancient alluvial cones deposited in the valley floor. The fact that these deposits are now found to have been sited indicates that the valley bottom has gradually been eroded by the action of common faults. Several generations of terraces have been seen on the canyon walls. Study results published in the journal Geology, therefore suggesting that the center of the valley gradually subsided for several generations of normal faults.

Wallace Marineris: No extension, but significant vertical movements

Despite some similarities with the valleys Crack Wider on Earth, the formation of Valles Marineris would therefore have been more associated with episodes of strong subsidence (procrastination) along vertical faults, with very little associated tectonic extension. Fluvial processes must have been active, at least sporadically, during the development of these basins.

Whereas, on Earth, the intensity of erosion processes is often faster than the filling of valleys. Speed In subduction conditions, these processes on Mars are apparently minor, indicating an inability of hydrological and climate systems to produce enough sediment to fill the basins that formed. However, the results suggest that the cyclicity of the deposits in Valles Marineris is linked to tectonic deformation, a first.

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Wallace Marineris: Plate Tectonics on Mars?

The last traces of plate tectonics on Mars have been discovered for a long time. UCLA planetary scientists believe they found it on the Red Planet while studying images from the probe Mars Odyssey and MRO. According to him, the great Martian canyon Wallace Marineris would be precisely linked to the existence of plate tectonics, which would also throw light on the puzzle of its existence.

article by laurent sacco, published 21 August 2012

This is the arrival of the probe into orbit around Mars Mariner 9 In 1971 who discovered Wallace Marineris. Images from this and subsequent spacecraft around the Red Planet showed that it was a massive system of canyons located nearEquator of this planet and extends for about 3,770 km. It is generally believed that this is a huge gapcollapsingWidened by erosion until reaching a width of 600 km at the local level. But it must be said that the origin of such a structure has remained a mystery for almost 40 years.

University planetary scientist An YinUCLA The recent unexpected in California has provided a new room for debate. binder The existence of Wallace Marineris in comparison to plate tectonics Mars planetMILF in a sea serpent Geology Inhabitant of Mars. For at least a decade, few published studies have suggested the presence of at least one tectonic plates In Mars’ past, the latter had then largely lost its heat reserves, one of the engines of the plates’ motion.

Presently, the presence of Volcano on its surface Olympus Mons clearly shows a priori that is no longer on Mars tectonic plates Like Earth for a long time. We can actually compare the formation of this volcano to the volcano of the islands airy on the earth. periodic growth of plums matter Intersects a peaceful plate moving on the hot earth. This is why many small volcanic islands are formed over time rather than a single volcano that rises continuously. On Mars, due to low gravity and the absence of plate tectonics more recently in its history, surface eruptions increased the height of Olympus Mons to 27 km.

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ESA’s European probe, in orbit of Mars, Mars Express, provides impressive images of its surface. one in this video flyover The vast Martian canyon, Valles Marineris, was reconstructedcomputer From test images. © Asa / DLR / Gerhard Neukum / YouTube

For some time, a yin was studying the images provided by the Themis instrument (Thermal Emission Imaging System) Mars Odyssey Probe and Hirise (high resolution imaging science experiment) aboard the Mars Reconnaissance Orbiter(MRO), is one of the tools that enables the creation of google mars.

Wallace Marineris, the boundary between the plates on Mars?

On Earth, Yin is well acquainted with the geomorphology and fault systems present in the Himalayas and Tibet. Unsurprisingly, a dozen images of Mars out of the hundred he was analyzing began to make connections with these fault systems associated with plate tectonics on Earth, and more precisely with the boundaries between plates.

Its original purpose was not to prove the existence of plate tectonics on Mars. But looking at the images of Wallace Marineris, it seemed clear to him that he was undergoing a horizontal sliding movement in the presence of a boundary between the two plates. Thus he discovered an impact crater located on either side of two plates, which were cut in two, which had slipped. We can see it well in the image below Google March. Sliding movement along the Valles Marineris valley has shifted these two parts by about 150 km.

According to Yin, Valles Marineris may therefore well be the boundary between two plates that are still moving but much slower than Earth. These movements would have occurred not every day but over a period of fault activity, perhaps every million years. on these occasions Earthquake Crucial end on Mars, for yin,” NS tectonic plates Mars is in the early stages. This gives us a glimpse of what Earth would have looked like and could help us understand the formation of tectonic plates on Earth. ».

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