Unusual Mars on Mars could help solve one of the greatest mysteries on the red planet

CNN
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Thousands of mysterious mounds on Mars preserve layers of evidence that point to the existence of ancient water on the red planet, which probably sculpted these imposing formations.

More than 15,000 mounds rise to heaven from the lowlands of Chryse plan on Mars, located near a natural dividing line between the southern and northern hemispheres of the planet. These geological characteristics have intrigued scientists for a long time, who until now were not sure what the mounds created.

The formations, which cover an area as large as Texas, can be seen in images taken by NASA orbiters and the European Space Agency (ESA) that revolve around the red planet. The unusual characteristics resemble the famous hills and plateaus of the Valley of the Monuments along the border between Arizona and Utah.

A new analysis of the images and data collected by the orbiters, published on January 20 in the journal Nature Geoscience, has shed light on the history of the mounds. The findings suggest why there could be such a marked difference between the northern and southern hemispheres of the planet: the erosion caused by water 4,000 to 3.8 billion years ago.

The mounds act as time capsules that could help astronomers unravel the secrets of Mars.

“Each mound is composed of a series of layers, each of which is a record of a past event,” said the main author of the study, Dr. Joe McNeil, planetary scientist and postdoctoral researcher at the Natural History Museum of London, by email. “The oldest are at the bottom and are composed of rock that has about 4,000 million years. For a geologist, looking at these layers is like looking at the pages of a book: Each account a story! ”

The mounds are close to the future landing site of the exomars rose Water on the red planet and point out resources for future human exploration.

Investigating Mars from space

McNeil and his team used images collected by the orbiters surrounding Mars to obtain information on the geology of the mounds. Orbiters carry sensors, cameras and other scientific instruments that collect a variety of data.

The mounds seemed similar to each other from a distance, but the high -resolution images captured by the orbitators allowed McNeil to approach, revealing an “incredible variety in their structure.”

While the hills and plateaus of the Valley of the Monuments can reach up to 1,000 feet (300 meters) on the floor of the valley and cover an area of ​​375 square meters, the Martian mounds reach 1,800 feet (550 meters) and extend through an area 2,000 times bigger, McNeil said. Martian mounds are also much older, existing for billions of years, instead of millions.

However, McNeil’s analysis shows that Martian mounds are probably the last remains of old highlands that were razed and worn out, formed very similar to the characteristics of the valley of monuments through erosion.

“Our findings reveal that the water was present both on the surface and in the subsoil of this region during geological time scales, between 4,000 million and 3.8 billion years ago,” McNeil said. “The mounds were originally part of the highlands, composed of hundreds of roca rich in clay that formed in the presence of liquid water. Its erosion along hundreds of kilometers shows that the highlands extended much more north than they do today, providing new ideas about the ancient geography and hydrology of Mars. ”

The layers of rich in clay inside the mounds suggest that there was an abundance of water on the surface of Mars, forming chemical reactions with the rocks. Water, either in liquid or ice form, could have caused erosion by infiltrating the rock fractures.

Although there is evidence that shows that rivers and caudalous lakes ever existed on Mars, it is difficult to say what type of aquatic characteristic caused erosion, McNeil said.

“Most of the evidence has been eroded, and what remains, the mounds, are so old that they have also had 3.8 billion additional years of wind erosion, in addition to what made them mounds first,” McNeil said.

“It’s like trying to understand the plot of a book where most pages are missing, and the remaining ones are torn and discolored. We can join part of the story, but much remains to the interpretation. ”

A question that McNeil and his colleagues explore in the study is whether an old North Ocean on Mars could have caused erosion, but the idea is controversial and discussed by scientists.

However, the robotic exploration of this region could determine if the ocean was ever present and if life could have existed in it.

Exploring a Martian mystery

The mounds are just north of what is known as the Martian dichotomy, a natural border between the shallow plains of the northern hemisphere and the highlands of the southern hemisphere. The highlands of the South are marked by craters and rise to 5 miles (8 kilometers) higher on average than the soft and undulating plains of the lowlands on them.

However, researchers have had difficulty identifying what the border created, which extends around the entire planet, resulting in one of Mars’s greatest mysteries, McNeil said. The appearance of this border varies around the planet, with some areas that seem to directly link the lowlands with the highlands, while others contain steep cliffs.

Scientists have two main theories about the origins of the border.

“Plate tectonics gives the earth its ocean continents and basins, but Mars does not have its own plaque tectonics,” McNeil said. “This means that it is difficult to explain why the highlands of southern Mars have a very thick and old cortex, while the lowlands of the north are very young and thin.”

“Some models have suggested that northern Mars was beaten by one or more giant impacts at the beginning of their history, effectively creating the lowlands of the north as a great depression,” he explained. “Alternatively, it could be the result of mantle processes similar to plaque tectonics, but ended quite early in the history of Mars.”

There is evidence for and against both theories, and the debate continues, McNeil said.

A study published in the January 16 edition of Geophysical Research Letters magazine suggests that Marsquakes, Or tremors inside Mars, detected by the now withdrawal Mission Insight of the NASA, they point to convection within the Martian subsoil as a driver of the dichotomy.

The convection, or the heat transfer from one place to another, probably took place in the mantle, or inner layer, from Mars billions of years ago, the authors of the study said. The mantle is between the cortex and the nucleus of the planet.

Approaching the mounds

McNeil began investigating the mounds of the Chryse region planning near the dichotomy as part of his doctoral program at Open University in England because he believes they are “an ideal place for future missions to Mars”.

Areas near the mounds, such as Oxia Planum and Mawth Vallis, are of interest to scientists because they can preserve past signs of life on Mars. The mounds cover the 310 miles (500 kilometers) between Mawth Vallis and Oxia Planum, but most of the mounds in the study are closer to Mawth Vallis, located in the lowlands to the north and west of the area.

Both Mawth Vallis and Oxia Planum were candidates for the future landing site of Rover Rosalind Franklin. However, the mission team has determined that Oxia Planum will provide a safer place to land and cross the land, according to ESA.

The mounds investigated in the study are hundreds of kilometers of Oxia Planum, but smaller mounds with the same composition on the landing site will be accessible so that the rover will observe them closely and photograph them.

“This is very exciting because it means that by exploring these plains, the rover will tell us a lot about the largest region and possibly about the environments that were present there and if they were habitable,” McNeil said. “(The mounds) were the key to understanding how all Mars area is connected.”

François Poulet, astronomer of the French Institute of Space Astrophysics that has studied the Mawth Vallis region, said he believes that McNeil’s study provides more details and evidence on how the mounds were formed. Poulet did not participate in the new study.

“This study reinforces my feeling that Mawth Vallis is really a unique region and one of the best regions to be explored by a future robotic mission,” Poulet said.