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Thousands of mysterious mounds March Preserve layers of evidence pointing towards old waters on the red planet which probably carved the imposing formations.
More than 15,000 mounds amount to the sky from the lowlands of the Mars Planitia Chrysum, located near a Line of demarcation between the southern and north hemispheres of the planet. The geological characteristics have long intrigued scientists, who so far did not know exactly what had created these mounds.
The training courses, which extend on an area as large as Texas, can be seen on the images taken by the NASA orbiters and the European Space Agency who revolve around the Red Planet. The unusual characteristics resemble the famous mounds and Mesas of Monument Valley, along the border between Arizona and Utah.
A new analysis of the images and data collected by the orbitors, published on January 20 in the journal Natural geosciencesHas highlighted the history of mounds. The results suggest why there could be such a marked difference between the north and southern hemispheres of the planet: the erosion caused by water 4 to 3.8 billion years ago.
The mounds act like temporal capsules that could help astronomers unravel the secrets of the past in March.
“Each mound consists of a series of layers, each of which is a recording of a past event,” said the main author of the study by email, Dr. Joe McNeil, planetologist and postdoctoral researcher at the Museum D ‘Natural history of London. “The oldest are at the bottom and are made up of rocks of around four billion years. For a geologist, watching these diapers is like looking at the pages of a book: each tells a story!
The mounds are located near the future landing site of the The Rover Exomars Rosalind Franklin de l’ESAwhose launch is planned in 2028. It is possible that the Rover is studying the mounds, which could reveal more about the history of water on the red planet and identify the resources for a future human exploration.
McNeil and his team used images collected by orbiters revolving around Mars to better understand the geology of mounds. Orbiters carry sensors, cameras and other scientific instruments that collect various data.
The mounds seemed like each other from afar, but the high resolution images captured by the orbiters allowed McNeil to zoom, revealing “an incredible variety in their structure”.
While the Valley monument mounds and mesas can reach up to 1,000 feet (300 meters) above the bottom of the valley and cover an area of 145 square miles, the Martian mounds reach 1,800 feet (550 meters) and Extend an area 2,000 times larger, said McNeil. . Martian mounds are also much older, since they have been around for billions of years rather than millions.
But McNeil’s analysis shows that Martian mounds are probably the last vestiges of old highlands which have been carried away and worn, formed in the same way as the elements of monument Valley by erosion.
“Our results reveal that water was present on the surface and in the subsoil of this region on geological time scales, between 4.0 (billion) and 3.8 billion years,” said declared McNeil. “The mounds were originally part of the highlands, made up of hundreds of meters of rocks rich in clay which were formed in the presence of liquid water. Their erosion over hundreds of kilometers shows that the highlands extended a lot (further) further north than today, offering new perspectives on the old geography and hydrology of March.
The rocky layers rich in clay inside the mounds suggest that an abundance of water was present on the surface of Mars, causing chemical reactions with the rocks. The water, in liquid or icy form, could have caused erosion by infiltrating the fractures of the rocks.
Although there is evidence demonstrating that raging rivers and lakes used to exist on Mars, it is difficult to say what type of body of water caused erosion, said McNeil.
“Most of the evidence has been eroded, and what remains – the mounds – are so old that they also underwent an additional 3.8 billion years of wind erosion in addition to what formed them at the start”, said McNeil.
“It’s like trying to understand the intrigue of a book with which most of the pages are missing and the others are torn and discolored. We can reconstruct a part of the story, but a large part is left to interpretation.
A question that McNeil and his colleagues explore in the study is whether a former Nordic Ocean on Mars could have caused erosion, but the idea is controversial and debated by scientists.
However, the robotic exploration of this region could determine whether the ocean has always been present – and if life could have existed there.
The mounds are found just north of what is called Martian dichotomy, a Frontier between the shallow plains of the northern hemisphere and the highlands of the southern hemisphere. The high lands in the south are strongly crafted with craters and rise on average up to 8 kilometers higher than the smooth and hilly plains of the bass lands above them.
But the researchers found it difficult to identify what created the border, which extends around the whole planet, which leads to one of the greatest mysteries in March, McNeil said. The appearance of this border varies through the planet, certain areas seeming to directly link the low lands to the highlands, while others contain steep cliffs.
Scientists have two main theories on the origins of the border.
“”Plates tectonics “Give the earth its continents and its ocean basins, but Mars does not have clean plates tectonics,” said McNeil. “This means that it is difficult to explain why the highlands in the south of March have a very thick and old crust, while the low lands of the North are very young and thin.
“Some models suggest that the north of March was struck by one or more giant impacts at the start of its history, thus creating the low lands of the North in the form of a large depression,” he explained. “Alternatively, this could be the result of processes induced by the mantle, similar to plates tectonics, but which ended quite early in the history of March. »»
There is evidence for and against the two theories, and the debate is raging, said McNeil.
A study published in the January 16 issue of the journal Geophysical research letters suggests that earthquakes, or tremors from March, detected by the current retired NASA Insight Mission underline convection in the Martian subsoil as the engine of the dichotomy.
Convection, or heat transfer from one point to another, probably took place in the mantle, or inner layer, from March billions of years ago, according to study authors. The coat is located between the crust and the core of the planet.
McNeil began to study the mounds of the Chryse Planitia region close to dichotomy in the context of his doctoral program while he was at Open University in England, because they think they constitute “a privileged location for Future missions on Mars ”.
The areas close to the mounds, such as Oxia Planum and Mawrth Vallis, interest scientists because they could preserve signs of life spent on Mars. The mounds extend over 500 kilometers between Mawrth Vallis and Oxia Planum, but the majority of the mounds in the study are closer to Mawrth Vallis, located in the bass lands in the north and west of the region.
Mawrth Vallis and Oxia Planum were candidates for the future landing site of Rover Rosalind Franklin. But the mission team determined Oxia Planum goes Provide a safer site to land and cross the land, according to the ESA.
The mounds studied in the study are hundreds of kilometers from Oxia Planum, but smaller mounds with the same composition to landing The site will be accessible to the rover To observe closely and to photograph.
“It is very exciting because it means that by exploring these plains, the rover will tell us a lot about the region as a whole, and possibly on the environments present there and if they were habitable,” said McNeil. “(The mounds) were the key to understanding how this March area is connected to each other.”
François Poulet, astronomer at the French Institute of Spatial Astrophysics which has studied the Mawrth Vallis regionsaid he thought that McNeil’s study provided more details and evidence on how the mounds have formed. Chicken was not involved in the new study.
“This study strengthens my feeling that Mawrth Vallis is truly a unique region and one of the best regions to be explored by a future robotic mission,” said Chicken.