Martian winds make rocks roll to form organized patterns

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Washington, Jan 10 (ANI): A new research has determined that rocks on Mars are on the move, rolling into the wind and forming organized patterns.

Images taken by the Mars Exploration Rover Spirit show small rocks regularly spaced about 5 to 7 centimeters apart on the intercrater plains between Lahontan Crater and the Columbia Hills.

The new finding counters the previous explanation of the evenly spaced arrangement of small rocks on Mars.

That explanation suggested that the rocks were picked up and carried downwind by extreme high-speed winds thought to occur on Mars in the past.

Although Mars is a windy planet, it would be difficult for the wind to carry the small rocks, which range in size from a quarter to a softball, according to Jon D. Pelletier, associate professor of geosciences at The University of Arizona in Tucson.

Pelletier and his colleagues suggest that wind blows sand away from the front of the rock, creating a pit, and then deposits that sand behind the rock, creating a hill. The rock then rolls forward into the pit, moving into the wind.

As long as the wind continues to blow, the process is repeated and the rocks move forward.

"You get this happening five, 10, 20 times then you start to really move these things around," said Pelletier. "They can move many times their diameter," he added.

The process is nearly the same with a cluster of rocks.

However, with a cluster of rocks, those in the front of the group shield those in the middle or on the edges from the wind, according to Pelletier.

Because the middle and outer rocks are not directly hit by the wind, the wind creates pits to the sides of those rocks.

Therefore, they roll to the side, not directly into the wind, and the cluster begins to spread out.

To investigate the regular patterns of the rocks on Mars, Pelletier combined three standard numerical computer models.

The first modeled air flow, the second modeled erosion and deposition of sand and the third modeled the rocks' movement.

He also conducted what is known as a Monte Carlo simulation, which applies his combination numerical model over and over to a random pattern of rocks to see how the rocks ultimately end up.

Pelletier ran the simulation 1,000 times. The rocks ended up into a regular pattern 90 percent of the time.

As an independent verification, he also compared the pattern predicted by the numerical model to the distances between each rock and its nearest neighbor in the Mars images.

The patterns of the Martian rocks matched what the model predicted. (ANI)

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