Just like Earth, Mars has vast expanses of rippled sand, but thanks to the tireless work of NASA's rover Curiosity, a new type of them has been discovered.
Said Mathieu Lapotre, one of the collaborators for the Curiosity mission, "Earth and Mars both have big sand dunes and small sand ripples, but on Mars, there's something in between that we don't have on Earth."
Such land formations, called impact ripples, generally occur as wind blows particles across the land, causing them to collide with one another and form peaks and rifts.
However, Lapotre noted, "As Curiosity was approaching the Bagnold Dunes, we started seeing that the crest lines of the...ripples are sinuous. That is not like impact ripples, but it is just like sand ripples that form under moving water on Earth."
That suggests Mars once had a much thicker atmosphere, and ripples hailing back to that time may provide insights into how it thinned over the eons.
RELATED: See photos of curiosity:
This image from Curiosity's Mastcam shows inclined beds of sandstone interpreted as the deposits of small deltas fed by rivers flowing down from the Gale Crater rim and building out into a lake where Mount Sharp is now. It was taken March 13, 2014, just north of the "Kimberley" waypoint.
This March 25, 2014, view from the Mastcam on NASA's Curiosity Mars rover looks southward at the Kimberley waypoint. In the foreground, multiple sandstone beds show systematic inclination to the south suggesting progressive build-out of delta sediments in that direction (toward Mount Sharp).
This image shows inclined beds characteristic of delta deposits where a stream entered a lake, but at a higher elevation and farther south than other delta deposits north of Mount Sharp. This suggests multiple episodes of delta growth building southward. It is from Curiosity's Mastcam.
This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover on Aug. 7, 2014, shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.
This image shows an example of a thin-laminated, evenly stratified rock type that occurs in the "Pahrump Hills" outcrop at the base of Mount Sharp on Mars. The Mastcam on NASA's Curiosity Mars rover acquired this view on Oct. 28, 2014. This type of rock can form under a lake.