Lurking inside a giant crater on the planet Mars, an immense dark spot is moving slowly, gaining momentum. Since its first observation around fifty years ago, scientists have wondered about the exact reason for the phenomenon, which has still not been precisely determined. Live Science, which took a close interest in the subject, reviews the details of this intriguing file.
This dark structure is an area covered in ash and volcanic rocks, such as olivine and pyroxene, from ancient eruptions that occurred millions of years ago, before Mars was considered geologically dead. It is located in Utopia Planitia, a plain about 3,300 kilometers wide in the northern hemisphere of Mars.
Two credible hypotheses
It was in 1976, shortly after their arrival on the red planet, that the probes viking from NASA photographed the blackened ground for the first time. Since then, several photos have shown that this formation extends over the surrounding landscape. We owe the most recent ones to the European Space Agency’s (ESA) Mars Express probe: they were taken in 2024 and published on April 15.
It is difficult to know exactly the extent of this gray area. However, according to the latest ESA images, portions of its southern boundary have moved south by at least 320 kilometers, suggesting that this dark terrain is expanding by about 6.5 kilometers per year. Some scientists are convinced that the movement of this dark spot is linked to Martian winds, known to sweep across the surface and kick up ash and dust, but much remains to be proven.
In a press release, ESA representatives explain that “the dispersion of the ashes over the past fifty years can be explained in two ways: either they were lifted and moved by Martian winds, or the ocher dust that previously covered the dark ashes was blown away by the wind”. For the moment, it is very difficult to determine which of the two hypotheses should be retained.
