A cluster of unusual dunes is observed on the planet Mars by the Mars Reconnaissance Orbiter (MRO), which flies at an altitude of 300 kilometers above the surface of the Red Planet.

Planetary scientists have observed near-perfectly round dunes, a rare occurrence on Mars where the dunes are chaotic and irregular.

Their slight asymmetry shows that their steep sides face south, which is a subtle imprint of winds blowing in the same direction.

The photo was taken by a HiRise high-resolution camera operated by scientists at the University of Arizona.

With these images, the researchers track how the ice on the surface of Mars retreats and melts as winter approaches. An earlier image of the same dunes shows dunes covered with ice.

This is just one of 60 sites on Mars controlled by HiRise MRO. The high-definition camera has been in orbit around the Red Planet since 2006, when the MRO reached Mars.

Repeated observations of the dunes during the Martian year, which lasts 687 Earth days, allowed planetologists to fix the speed of the dunes. From the equator to the poles, these structures move one meter per Martian year.

The main MRO mission ended on December 21, 2010, five years and six months after its launch from Earth on August 12, 2005. This new image shows that even 12 years after the end of the mission, the spacecraft and HiRise still provide valuable data for scientists.

Source: NASA, Space.com.