When Percival Lowell first looked at Mars through his telescope in the 1890s, he saw some remarkable patterns: connecting lines crisscrossing the surface, linking distant ends of the planet in a seemingly non-natural way. Lowell subscribed to Italian astronomer Giovanni Schiaparelli’s interpretation that the lines were canals deliberately constructed by intelligent beings to transport water. And he felt the need to spread the word, writing an increasingly bold trilogy as his convictions deepened: Mars, Mars and Its Canals, and Mars As the Abode of Life.
Several decades later, the Mariner 4 spacecraft flew past the Red Planet, snapping pictures like a speeding paparazzo. The results were disappointing: the grainy photographs showed craters frozen in time, evidence of a brutal bombardment in the planet’s past. And there certainly weren’t any well-constructed canals.
These two examples represent the stark extremes of our perception of Mars, from a world of actively changing surfaces to one of a static, frozen wasteland. Subsequent missions have pointed to a reality that is somewhere in between, but recent findings from NASA’s Mars Reconnaissance Orbiter mission offer unprecedented resolution on dynamic sand dune activity.
Software engineers and image analysts based at the California Institute of Technology, or Caltech, examined pictures from the High Resolution Imaging Science Experiment (HiRISE) camera. This camera is a 30 cm-per-pixel powerhouse that, ironically, is better than publically available images of our own planet. (According to Caltech, images of Earth-based targets taken at a similar resolution are classified information.)
The team looked at HiRISE images taken 105 days apart within the 300 square kilometer Nili Patera dune field and used an advanced processing program to detect subtle changes in dune shape and coverage. To their surprise, they saw movement – up to 4.5 meters – and not just in isolated cases. In fact, according to software engineer Francois Ayoub, who contributed to the study, “in the footprint covered by our analysis, all of the dunes imaged are active. No dune seems static.”
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