NASA's Mars rover Curiosity has discovered an expanse of medium-sized sand waves unlike any sand types discovered on Earth.
The newly discovered Bagnold Dunes are located in the northwestern flank of Mount Sharp.
The ripples found at Bagnold Dunes feature characteristics of both types of waves -- larger impact ripples with one side of each dune steeper than the other.
Lapotre says that wind-drag ripples aren't caused by the slow shaping that accumulates as dunes, nor by the the aerial acrobatics that create small ripples.
"The size of these ripples is related to the density of the fluid moving the grains, and that fluid is the Martian atmosphere," Mathieu Lapotre, a graduate student at Caltech and scientist on the Curiosity mission, said in a news release.
"We think Mars had a thicker atmosphere in the past that might have formed smaller wind-drag ripples or even have prevented their formation altogether," Lapotre continued. "Thus, the size of preserved wind-drag ripples, where found in Martian sandstones, may have recorded the thinning of the atmosphere."
Lapotre and his colleagues have already discovered a use for this new dune discovery. Dunes of all sizes can leave their fingerprint as they form sedimentary rock after eons.
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is often referred to as the "Red Planet". Mars can easily be seen from Earth with the naked eye, as can its reddish coloring.
