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Mars rover heads for active dunes

No Mars rover has yet visited a sand dune, as opposed to smaller sand ripples or drifts. Curiosity will visit actual Mars dunes in the next few days.

This Sept. 25, 2015, view from the Mast Camera on NASA's Curiosity Mars rover shows a dark sand dune in the middle distance.  Image credit: NASA/JPL-Caltech/MSSS

This September 25, 2015, view from the Mast Camera on NASA’s Curiosity Mars rover shows a dark sand dune in the middle distance. Image credit: NASA/JPL-Caltech/MSSS

NASA’s Curiosity rover will get a first close-up look at Martian sand dunes in the next few days, when it visits the dark dunes called the Bagnold Dunes. Mars rovers have visited smaller sand ripples or drifts, but no actual mobile sand dunes so far. One of the dunes Curiosity will investigate is as tall as a two-story building and as broad as a football field. As of November 16, 2015, Curiosity has about 200 yards or meters remaining to drive before reaching the first dune.

The Bagnold Dunes are active, or mobile. Images from orbit indicate some of them are migrating as much as about 3 feet (1 meter) per Earth-year. No active dunes have been visited anywhere in the solar system besides Earth.

This animation flips back and forth between views taken in 2010 and 2014 of a Martian sand dune at the edge of Mount Sharp, documenting dune activity. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

This animation flips back and forth between views taken in 2010 and 2014 of a Martian sand dune at the edge of Mount Sharp, documenting dune activity. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

The rover is already monitoring the area’s wind direction and speed each day and taking progressively closer images. At the dune, it will use its scoop to collect samples for the rover’s internal laboratory instruments, and it will use a wheel to scuff into the dune for comparison of the surface to the interior.

This map shows the route driven by NASA's Curiosity Mars rover from the location where it landed in August 2012 to its location in mid-November 2015, approaching examples of dunes in the

This map shows the route driven by NASA’s Curiosity Mars rover from the location where it landed in August 2012 to its location in mid-November 2015, approaching examples of dunes in the “Bagnold Dunes” dune field. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

Curiosity is on its way to higher layers of a mountain called Mount Sharp, where it is investigating how Mars’ ancient environment changed from wet conditions favorable for microbial life to harsher, drier conditions. The Bagnold Dunes skirt the northwestern flank of Mount Sharp
Curiosity has driven about 1,033 feet (315 meters) in the past three weeks, since departing an area where its drill sampled two rock targets just 18 days apart.

Before Curiosity’s landing, scientists used images from orbit to map the landing region’s terrain types in a grid of 140 square quadrants, each about 0.9 mile (1.5 kilometers) wide. Curiosity entered its eighth quadrant this month. It departed one called Arlee, after a geological district in Montana, and drove into one called Windhoek, for a geological district in Namibia. Throughout the mission, the rover team has informally named Martian rocks, hills and other features for locations in the quadrant’s namesake area on Earth.

The dark band in the lower portion of this Martian scene is part of the

The dark band in the lower portion of this Martian scene is part of the “Bagnold Dunes” dune field lining the northwestern edge of Mount Sharp. Image credit: NASA/JPL-Caltech/MSSS

What distinguishes actual dunes from windblown ripples of sand or dust, like those found at several sites visited previously by Mars rovers, is that dunes form a downwind face steep enough for sand to slide down. The effect of wind on motion of individual particles in dunes has been studied extensively on Earth, a field pioneered by British military engineer Ralph Bagnold (1896-1990). Curiosity’s campaign at the Martian dune field informally named for him will be the first in-place study of dune activity on a planet with lower gravity and less atmosphere.

Nathan Bridges of the Johns Hopkins University’s Applied Physics Laboratory, Laurel, Maryland, leads the Curiosity team’s planning for the dune campaign. Bridges said:

These dunes have a different texture from dunes on Earth. The ripples on them are much larger than ripples on top of dunes on Earth, and we don’t know why. We have models based on the lower air pressure. It takes a higher wind speed to get a particle moving. But now we’ll have the first opportunity to make detailed observations.

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Bottom line: NASA’s Curiosity rover will get its first close-up look at Martian sand dunes in the next few days, dark dunes called the Bagnold Dunes. No Mars rover has yet visited a sand dune, just smaller sand ripples or drifts so far. One dune Curiosity will investigate is as tall as a two-story building and as broad as a football field. As of yesterday, (November 16, 2015) Curiosity has about 200 yards or meters remaining to drive before reaching the first dune.

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