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Ripples in Endurance Crater. Credit: NASA/Space Science Institute/Opportunity Rover

 

Nov 06, 2008
Martian Ripples

An analysis of Mars Orbiter Camera images suggests an explanation for the ripples that cover large areas of Mars.

Recently, NASA investigators announced that the "strange ripples of sand" covering thousands of square kilometers on Mars might have been created by wind. However, information from the Mars Rovers Spirit and Opportunity, as well as older mission catalogs, casts doubt on that conclusion.

The ripples are known as Transverse Aeolian Ridges (TAR) and were seen on the Martian surface as long ago as November 1971 when Mariner 9 (the first spacecraft to enter orbit around another planet and for which the giant chasm Valles Marineris was named) returned what were, for its day, high resolution images of the surface. Now, after analyzing thousands of images taken by the Mars Orbiter Camera, the TARs appear to be more prevalent in the southern latitudes, although they tend to cluster 30 degrees north and south of the equator. One other interesting aspect is that they occur under two conditions: near extremely large barchan-type dunes composed of dark, grainy material, often found in conjunction with tightly layered topography, and in the bottoms of craters, regardless of size.

It is assumed that sand dunes on Earth form because wind and rain tear apart the rocks over eons of time, thus providing that large volume of sedimentary dust particles necessary for deserts like those in Namibia, or Egypt, or anywhere else, to form. Next, high winds are needed to lift and carry the small bits of sediment and eventually pile them up in drifts. Sand dunes on Earth are normally seen to move across the landscape in that way, through wind action. Enormous volumes of soil, in the millions of tons, are transported around the planet every year because of common weather patterns.

When planetary scientists find sand ripples or dunes on other planets, the natural assumption is that similar activity created what look to be similar formations. Although the environment that currently exists on Mars is not conducive to Earth-like erosion, the landforms are so much alike that the conclusion is that Mars was once capable of sustaining winds and rain. However, is projecting what we see on Earth onto other worlds be the right way to go? Or should we be using the evidence accumulated from other worlds as a guide for what might have happened here?

Sand dunes and ripples do not move around Mars, at least as far as any observations can demonstrate. From the time of the Viking orbiter until the HiRise camera system, no dunes have been seen to move at all despite several planet-wide dust storms. Some research has suggested that a small dune on Mars might take more than a thousand years to move a meter. This is due to the low pressure of the Martian atmosphere—not enough force needed to push the particles can be generated by the speed of the wind if the atmosphere in which it blows is close to a vacuum.

Since the Mars Rovers have been unable to "feel" any wind even during the storms, support for the electric dust storm model advocated by Electric Universe proponents gains ground and Earth-based models of weathering on Mars breaks down. In fact, some dune formations on Mars appear to be frozen in place with a crusty surface that looks as if it has been eroded. Electrical theorists predict that the more scientists learn about these formations the less plausible the traditional explanations will become.

False color images of dune formations in Rabe crater from the THEMIS camera, for example, provide important information about the relative hardness of different surface areas. "Hardness" is deduced from overnight surface temperatures, the warmer temperatures indicated in red, and the cooler ones indicated in blue. Considering that criteria, the crests of the so-called “dunes” are significantly harder than the valleys between them. Such a revelation is certainly counterintuitive if they are windblown features.

Most formative processes on Mars seem to bear little actual resemblance to textbook geology. The lack of movement and the hardness of the dunes (and the ripples) suggests that they were solidified and have remained in place since they were initially formed. In other words, they were glassified and fused together into immobile structures while retaining the appearance of loosely piled sand. Cathode sputtering and subsequent electrical deposition of the finely divided material onto oppositely charged regions across the surface could explain the ersatz dunes.

There is also the fractal-like reduction in scale when considering ripples and dunes. Even small dune "tendrils" have smaller ripples. Dune crests like those in Rabe crater can be 200 meters high, while the tendrils are no more than ten centimeters but with the same morphology. What aeolian process can account for this progressive fractal reduction in scale? In electrical terms this is no anomaly since plasma discharges are scalar across many orders of magnitude.

NASA scientists often refer to what they find on Mars as "mysterious" or "puzzling" with long years of research and contemplation ahead of them. We predict that the reason for the confusion is the problem of reverse application. Earth should not be used to explain the solar system. The geological patterns found elsewhere deserve alternative viewpoints. The entire issue of Martian ripples is a case in point.

By Stephen Smith

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