Factors other than trapped ice limit dune movement on Mars

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Washington, July 8 (ANI): A study has determined that snow and ice trapped inside dunes on Mars does not entirely stop their movement, a finding which indicates that other factors are limiting the dune movement.

Planetary scientists have monitored some Martian sand dunes for more than 30 years, and the dunes have not moved during that time, leading scientists to question whether snow and ice trapped inside the dunes might be preventing movement.

However, a recent study, led by Mary Bourke, a senior research scientist at the Tucson-based Planetary Science Institute, shows that snow and ice are not enough in themselves to stop dune movement.

While trapped ice and snow impedes movement of sand dunes in polar climates, compared to their counterparts in warmer areas, this does not entirely stop dune movement, the study shows.

"This indicates that other factors are limiting dune movement," said Bourke.

Bourke also showed that two small dunes recently disappeared on Mars. The dunes, which were 20 meters wide (about 65 feet) and located in the north polar region of Mars, were completely eroded away over a period of 5.7 Earth years.

"This (dune disappearance) is fantastic new data, showing that sand is transported on Mars where and when the wind energy is available," Bourke said. "But the bigger, larger dunes on Mars are not moving, at least in the areas we studied," she added.

In the most recent study, Bourke and her colleagues used vertical aerial photos and LiDAR (Light Detection and Ranging) data to estimate dune migration rates in Antarctica's Victoria Valley dune field.

The photos, taken between 1961 and 2001, came from the USGS Antarctic Resource Center.

These dunes are known to be covered by seasonal snowfalls and have snow and ice layers trapped inside.

Bourke found that the dunes migrated about 1.5 meters (5 feet) per year, which is small compared to the distance covered by dunes in warm deserts, which can be as high as 30-70 meters (about 100 to 230 feet) a year.

Factors limiting dune movement on Mars would include the planet's thin atmosphere, which requires very high wind speeds to provide the force needed to move sand, and the water and carbon-dioxide frosts that cover dunes in Mars' polar regions for 70 percent of the year. (ANI)

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