Dramatic Wind Action Detailed On Mars

[n2doc]

ScienceDaily (Jan. 28, 2008) — Mars has an ethereal, tenuous atmosphere with less than one-percent the surface pressure of Earth, which challenges scientists to explain complex, wind-sculpted landforms seen with unprecedented detail in images from NASA's Mars Reconnaissance Orbiter.

f the main questions has been if winds on present-day Mars are strong enough to form and change geological features, or if wind-constructed formations were made in the past, perhaps when winds speeds and atmospheric pressures were higher.

The eye-opening new views of wind-driven Mars geology come from the University of Arizona's High Resolution Imaging Science Experiment camera (HiRISE). As the orbiter flies at about 3,400 meters per second (7,500 mph) between 250 and 315 kilometers (155 to 196 miles) above the Martian surface, this camera can see features as small as half a meter (20 inches).

"We're seeing what look like smaller sand bedforms on the tops of larger dunes, and, when we zoom in more, a third set of bedforms topping those," said HiRISE co-investigator Nathan Bridges of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "On Earth, small bedforms can form and change on time scales as short as a day."

There are two kinds of "bedforms," or wind-deposited landforms. They can be sand dunes, which are typically larger and have distinct shapes. Or they can be ripples, in which sand is mixed with coarser particles. Ripples are typically smaller and more linear.

more:

http://www.sciencedaily.com/releases/2008/01/080124191716.htm

This is what they are looking at:

Dust-devils are vortices of wind that form when air rising from a warm surface encounters shear in the above atmosphere. Martian dust devils can attain gargantuan proportions, reaching the size of terrestrial tornadoes with plumes that tower up to 9 kilometers above the surface. Dust-devils play an important role in sustaining the aerosols that make up Mars’ red sky and in cleaning the Martian surface after a dust storm.

This observation shows a region near the Martian equator that is a perfect tablet for the scribblings of dust-devils. This region is made up of dark bedrock that is thinly blanketed by bright dust. Dark tracks form when dust-devils scour the surface, exposing the darker substrate. The tracks tend to cluster together, as dust-devils repeatedly form over terrain that has been previously scoured and is consequently darker and warmer than the surrounding surface.

Once lofted by a dust-devil, the fine dust can be transported great distances before it settles again onto the surface.

[1620rock]

1. Wow, beautiful photo. It's reminiscent of a frozen snow scoured field on earth.