Curiosity Rover's Sand Dunes Study Reveals Another Surprise

NASA's study reveals that some sand dunes found on the surface of Mars are not so different from that seen on Earth and their relationship to the thin Martian atmosphere can provide new clues about the history of Mar's atmosphere.

The wind-sculpted mid-size ripples are distinct from those observed by NASA's Curiosity Rover before. The "Bagnold Dunes" were the subject of the rover's study six months ago, located in the northwestern part of Mount Sharp.

"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," Mathieu Lapotre, a graduate student at Caltech and science team collaborator for the Curiosity mission said in a statement. His study on mid-size ripples was published in the journal Science on July 1.

Both the Earth and Mars have their own sand dunes, some were even larger than football fields, shaped by winds with downwind faces shaped by avalanches that are steeper than upwind faces. According to NASA, the Earth has the same ripples in rows less than a foot apart. Sand grains carried by the wind formed these sand dunes, the "impact ripples" corrugate the surfaces of sand dunes and beaches.

The Curiosity Rover has taken photographs of sand dunes, some at 10 feet apart. But the Bagnold Dunes proved that the ripples on Mars could be several times larger than the impact ripples on Earth.

"As Curiosity was approaching the Bagnold Dunes, we started seeing that the crest lines of the meter-scale ripples are sinuous," Lapotre said in a statement published by Phys.Org. "That is not like impact ripples, but it is just like sand ripples that form under moving water on Earth. And we saw that superimposed on the surfaces of these larger ripples were ripples the same size and shape as impact ripples on Earth."

Some other similarities of Martian sand dunes ripples and Earth's underwater ripples are the face of each ripple is steeper that the face on the other side and has sand flows, as in a dune. On Mars, researchers suggest that this is due to the Martian wind dragging sand particles the way flowing water drags sand particles on Earth. It's a different way of how the dunes and ripples form that experts call "wind-drag ripples."

Studying the new type of ripples found on the surface of Mars could provide historical clues on the evolution of the planet since the dunes can be preserved into rocks over time. "Because the size and wavelength of these ripples vary with the density of the atmosphere under which they form, we can search for preserved "fossil" wind-drag ripples in ancient sedimentary rocks on Mars, and constrain how thick the atmosphere was at the time of deposition of the rock," Lapotre said in a interview with DailyMail.