New types of sand ripples? A new understanding of Mars’ history.
Last week, a report about mid-size sand ripples was published in Science. Through evaluating sand features on Mars, researchers have learned more about the planet’s early atmosphere.
Earth and Mars both have large sand dune features which are generally bigger than a football field. On Earth, small sand ripples are usually less than a foot apart and appear in rows. These small ripples are called “impact ripples” and some appear on sand dunes and beach surfaces. They are formed as grains of sand are carried by the wind and impact other sand grains on the ground.
Before the Curiosity rover studied impact ripples on Mars up close six months ago, the best images we had of them came from orbit. Images showed ripples on the surface of dunes around 10 feet apart. The resolution of these images did not allow sand features on the scale of Earth’s small ripples to be seen. As a result, it was interpreted that Mars’ impact ripples could be several times bigger than Earth’s impact ripples.
NASA/JPL-Caltech/MSSS
When Curiosity approached the “Bagnold Dunes,” researchers did not see impact ripples but rather ripples that resembled those formed on Earth under moving water. These mid-size ripples also had one steeper face just like underwater ripples on Earth.
How were these meter-scale ripples formed? Researchers believe that sand particles were dragged by the wind on Mars just as sand particles on Earth are dragged by flowing water. The recent report refers to them as “wind-drag ripples.” Studying mid-size ripples of sand on Mars contributes to evidence that most of the planet’s original atmosphere was lost long ago in the planet’s early history.
The Curiosity rover is managed by NASA’s Jet Propulsion Laboratory as the Mars Science Laboratory evaluating the planet’s environment and whether it ever supported small life forms.