Strange, difficult-to-explain circular structures were recorded by the HiRISE camera mounted on NASA’s Mars Reconnaissance Orbiter (MRO).

According to NASA, the images were taken in a sand field at latitude 42.505 degrees and longitude 67.076 degrees, showing almost perfectly circular structures, looking like flying saucers or carefully strung tents, evenly on sand.

MRO captured the breathtaking view while flying about 300 km above the surface of Mars, so the mysterious circular structures would be huge if you stood looking at the red planet’s surface.

NASA says these structures are sand dunes and not something created by aliens. If you look closely, you will see a slight asymmetry in these “near perfect” circles, indicating that their slopes face south, meaning the sand is blown south.

According to Space, this new collection of MRO images aims to track the process of frost receding and melting on the surface of Mars, as the red planet ends its winter. The image with the nearly black sand dunes is when the frost has gradually receded, while an earlier image with rounder “sand flying saucers” is when the frost still covered the surface of Mars.

NASA did not give a specific explanation for how the dunes were formed in their strange shape, but said that in addition to this place, they also monitor 90 other locations with HiRISE.

Collecting repeated observations of sand dunes allows planetary scientists to capture their speed of movement. This revealed that Martian equatorial magnetic dunes are moving toward the poles at a rate of 1 meter per year.

MRO has recorded many other strangely shaped sand dunes, revealing many details about the red planet’s weather. This is a long-standing Mars reconnaissance ship, which ended its 5.5-year main mission on December 21, 2010. However, so far it is still working well and continues to contribute to NASA.