For the first time, an international team of planetary scientists, including David Vaz, from the Earth and Space Research Center at the University of Coimbra (CITEUC), observed the movement of giant sand waves, called megaripples (“megaondulations”), on the planet Mars.
This discovery, the result of about a decade of observations (between 2007 and 2016), is of particular relevance, since, until now, it was thought that these structures – because they are made up of thicker sand particles – would not be active (the wind would not currently be able to move these particles).
“As there was no evidence that they were moving, it was believed that they would be ‘relics’ of the strongest wind activity that would have existed in the past on Mars. However, our observations are quite conclusive and contradict this view, that is, the megaripples on Mars are definitely active”, explains David Vaz.
In order to reach this conclusion, that “megaondulations” are moving around the red planet, albeit slowly (about 10 centimeters per year), the team led by Simone Silvestro, from INAF-Osservatorio Astronomico di Capodimonte (Italy), analyzed more than a thousand of these sedimentary structures, using high-resolution images acquired by NASA’s Mars Reconnaissance Orbiter, in two regions of Mars: McLaughlin crater and Nili Fossae.
The participation of the CITEUC researcher in this discovery was centered on the “processing of the surface images obtained by the probe and the application of various techniques, developed previously, that allow to measure with great precision the sediment flows (transport speed and quantity of sediments transported by wind) on the surface of Mars”.
“In this study it was particularly important to measure the speed and the way in which megaripples, a specific type of ripples that are formed by the transport of sediments due to the action of the wind, moved over a period of time of almost 10 earth years”, he underlines.
David Vaz also contributed with a set of measurements of migration velocity and sedimentary flows to dunes from other regions of Mars, “which served to frame and explain the observations made in the two areas in which the study focuses”, having also participated in the work that took place in the Moroccan desert in 2017 and 2019, where “terrestrial megaripples” were studied. This work, in essence, served as a preparation and inspiration for the discoveries that we later made on Mars”. This is because the phenomenon observed on Mars is also registered on Earth, although at very different scales and speeds.
Also according to David Vaz, PhD in Geology from the Faculty of Science and Technology of the University of Coimbra (FCTUC), this study “is important because it demonstrates, for the first time, that these sedimentary structures (megaripples) are active, and that the wind on the Martian surface it will be strong enough to move larger particles, that is, this discovery confirms that Mars is a very active planet from a geological point of view, even at much lower speeds than on Earth, geological processes continue to shape the planet’s surface”.
The team, which also includes scientists from Università degli Studi “Gabriele d’Annunzio” (Italy), Lunar and Planetary Laboratory, University of Arizona (USA), Planetary Science Institute (USA) and Ben ‐ Gurion University of the Negev (Israel), now intends to extend the investigation of megaripples to the entire planet Mars.