MARS Nili Patera: Sandblasting winds shift Mars' sand dunes

Migration orientation of sand ripples laying on top of Martian dunes in the Nili Patera area.

Sand ripple migration is tracked from the comparison of satellite images of the dune field acquired at different time. 

Credit: Francois Ayoub, Caltech

High winds are a near-daily force on the surface of Mars, carving out a landscape of shifting dunes and posing a challenge to exploration, scientists said Tuesday.

Wind has long been known to be a factor in the Red Planet's topography and climate, creating dust storms that can be visible to astronomers on Earth.

But data about the strength, frequency and origin of winds has been sketchy, and many specialists had expected that gusts strong enough to move sand would be rare on a planet with such a thin atmosphere.

"We observed that martian sand dunes are currently migrating and that their migration speed varies with the season, which is at odds with the common view of a static martian landscape and very rare sand-moving winds," study co-author Francois Ayoub of the California Institute of Technology's planetary sciences division told AFP.

Ayoub and a joint US-British team of scientists measured the displacement of sand ripples on a dozen satellite images taken of a 40-square-kilometre (15-square-mile) area in the Nili Patera dune field over one Mars Year.

"From these measurements, we estimated the sand flux and its seasonal variability," said Ayoub.

Next, they calculated the wind speed and strength required to move the sand, and the frequency.

"Winds on Mars can be strong and can reach hurricane speed (more than 120 kilometres per hour or 75 miles per hour)," Ayoub said.

"In our study area, sand-moving wind occurs almost daily" throughout much of the year, he added.

Understanding the characteristics of Mars' winds would allow scientists to make predictions about the rate of erosion of the landscape and about the martian climate, which is heavily influenced by dust in the atmosphere, and the data may aid future rover missions from Earth.

"An accurate prediction of the wind and sand load is important to avoid the rover to be 'sandblasted' without being prepared for it," explained Ayoub.

"The (NASA) rover Curiosity, which is about to cross an active dune field in Gale crater will most probably have to sustain sand blows."

"From a scientific point of view, these findings could indicate areas on Mars deserving more attention from observation orbiters for their peculiar wind/sand/erosion behaviours."

The study was published in the journal Nature Communications.

More information: Threshold for sand mobility on Mars calibrated from seasonal variations of sand flux, Nature Communications 5, Article number: 5096, dx.doi.org/10.1038/ncomms6096

ESA Earth Observation: Richat structure in the Sahara desert, Mauritania

Pictured here in this satellite image is the Richat structure, a giant, geological wonder in the Sahara Desert of Mauritania.

Credit: JAXA /ESA

The 40 km-diameter circular Richat structure is one of the geological features that is easier to observe from space than from down on the ground, and has been a familiar landmark to astronauts since the earliest missions.

Once thought to be the result of a meteor impact, researchers now believe it was caused by a large dome of molten rock uplifting and, once at the surface, being shaped by wind and water into what we see today.

Concentric bands of resistant quartzite rocks form ridges, with valleys of less-resistant rock between them.


The dark area on the left is part of the Adrar plateau of sedimentary rock standing some 200 m above the surrounding desert sands.

A large area covered by sand dunes (an erg) can be seen in the lower-right part of the image, and sand is encroaching into the structure’s southern side.

Zooming in on the southern side of the bullseye, we can see individual trees and bushes as tiny dots.

These follow a river-like structure that appears to have been dry when this image was acquired, a few weeks after the rainy season.

Some areas to the south and east of the Richat appear to be covered with temporary lakes, which are dry for most of the year.

NASA Mars HiRise Image: MRO Captures Dark Sand Cascades

They might look like trees on Mars, but they're not.

Groups of dark brown streaks have been photographed by the Mars Reconnaissance Orbiter on melting pinkish sand dunes covered with light frost.

The above image was taken near the North Pole of Mars.

At that time, dark sand on the interior of Martian sand dunes became more and more visible as the spring Sun melted the lighter carbon dioxide ice.

When occurring near the top of a dune, dark sand may cascade down the dune leaving dark surface streaks -- streaks that might appear at first to be trees standing in front of the lighter regions, but cast no shadows.

Objects about 25 centimeters across are resolved on this image spanning about one kilometer.

Close ups of some parts of this image show billowing plumes indicating that the sand slides were occurring even when the image was being taken.

Cassini radar sees sand dunes on Saturn's giant moon Titan

Image credit: NASA/JPL (upper photo); NASA/JSC (lower photo)

Cassini radar sees sand dunes on Saturn's giant moon Titan (upper photo) that are sculpted like Namibian sand dunes on Earth (lower photo).

The bright features in the upper radar photo are not clouds but topographic features among the dunes.

The answer to the mystery of dune patterns on Saturn's moon Titan did turn out to be blowing in the wind. It just wasn't from the direction many scientists expected.

Basic principles describing the rotation of planetary atmospheres and data from the European Space Agency's Huygens probe led to circulation models that showed surface winds streaming generally east-to-west around Titan's equatorial belt.

But when NASA's Cassini spacecraft obtained the first images of dunes on Titan in 2005, the dunes' orientation suggested the sands - and therefore the winds - were moving from the opposite direction, or west to east.

A new paper by Tetsuya Tokano in press with the journal Aeolian Research seeks to explain the paradox. It explains that seasonal changes appear to reverse wind patterns on Titan for a short period. These gusts, which occur intermittently for perhaps two years, sweep west to east and are so strong they do a better job of transporting sand than the usual east-to-west surface winds.

Those east-to-west winds do not appear to gather enough strength to move significant amounts of sand.

A related perspective article about Tokano's work by Cassini radar scientist Ralph Lorenz, the lead author on a 2009 paper mapping the dunes, appears in this week's issue of the journal Science.

"It was hard to believe that there would be permanent west-to-east winds, as suggested by the dune appearance," said Tokano, of the University of Cologne, Germany. "The dramatic, monsoon-type wind reversal around equinox turns out to be the key."

The dunes track across the vast sand seas of Titan only in latitudes within 30 degrees of the equator. They are about a kilometer (half a mile) wide and tens to hundreds of kilometers (miles) long. They can rise more than 100 meters (300 feet) high.

The sands that make up the dunes appear to be made of organic, hydrocarbon particles. The dunes' ridges generally run west-to-east, as wind here generally sheds sand along lines parallel to the equator.

Scientists predicted winds in the low latitudes around Titan's equator would blow east-to-west because at higher latitudes the average wind blows west-to-east. The wind forces should balance out, based on basic principles of rotating atmospheres.