Wind writing across the dunes

Sand Dunes and Ripples in Proctor Crater, Mars — NASA/JPL-Caltech/University of Arizona
Event image. Small ripples run across larger dune forms inside Proctor crater.
NASA/JPL image-use policy · credited mission imagery, resized to WebP
· Original image source · Image licence

Ripples, dune crests and repeated observations reveal movement.

World: Mars
Case date or period: Image archive · 2009–2017

Look closer

Mars has several overlapping scales of wind-shaped texture. Follow the large dune forms, then the much smaller ripples that run across them; the directions do not always agree.

Follow the evidence

The Nili Patera comparison documents ripple movement between observations. Other images show different dune fields and opposing wind patterns. Compare form and scale without treating separate sites as a single time sequence.

From shifting ripples to moving dunes

The 2012 Nili Patera study compared HiRISE observations from 2007 and 2010. Its image-correlation measurements found faster ripple movement higher on the dunes; connecting displacement with position supported movement of whole dunes and estimates of transported sand volume. This went beyond noticing a changing outline. The accompanying 105-day ripple comparison was adjusted to an overhead view and aligned using fixed bedrock features, so lighting differences should not be mistaken for sand movement.

An independent image-processing comparison

Amelia Carolina Sparavigna’s 2013 preprint compared a 1999 Mars Global Surveyor image with a 2007 HiRISE view of Nili Patera. Brightness adjustment and a Sobel edge filter made a dune’s displacement against ground landmarks easier to see. The paper notes the cameras’ differing resolution and orientation. This is a processed comparison of existing observations, not new footage; its estimated movement of one dune should not be substituted for the mission study’s broader sand-flux measurements.

Stand beside a dune, then look down from orbit

The Namib mosaic lets you inspect fine ripples and tongues of sand on a steep slip face from rover height. Its exposures were taken in December 2015, and its colour was white-balanced for an Earth-daylight appearance. The Nili Patera view provides a separate orbital scale. Compare the textures across those scales, while keeping the sites distinct: the Namib photograph is not a later frame of the Nili Patera change study.