Scientists baffled by polygon mystery on Mars

May 28th, 2008 - 1:28 pm ICT by admin  

London, May 28 (ANI): Images received from the Mars Phoenix mission have surprisingly indicated that the polygons, which are typical features on the surface of the Red Planet, are smaller than previously believed.

According to a report in New Scientist, these images have left scientists baffled because of an unexpected difference between what they thought they would see and what Phoenix is now showing them.

Since landing on the surface of Mars on May 26, NASAs Phoenix has been relaying images and data back to Earth via the Mars Odyssey orbiter, which periodically passes over the landing site.

Among the most spectacular images so far is a colour mosaic of the terrain looking out from the northward side of the lander. It clearly shows the so-called polygons that are typical features of this region.

Polygons are produced by seasonal expansion and contraction of ground ice. When the ice is very cold, it contracts and fractures in geometric patterns, much like mud cracks in the desert.

But, the problem is that the Phoenix images have shown the polygons on Mars are too small.

According to principal investigator Peter Smith of the University of Arizona, Tucson, US, preliminary estimates suggest the polygons in the foreground of the image are about 1.5 to 2.5 metres across.

This is much smaller than scientists estimated based on overhead views from the Mars Reconnaissance Orbiter and on models of the Martian climate.

I think it means that there are polygons within polygons within polygons, said Smith. At different climate times, there may have been big polygons and at other times there may be small polygons, and it just may go back and forth over time, he added.

The potential for using polygon sizes to investigate the Martian climate is something that mission scientists have been preparing for since long before Phoenix was launched.

We knew they would be there, but we didn’t know what they would look like, said Michael Mellon, a Phoenix mission team member at the University of Colorado.

According to Mellon, the size of these polygons should be affected by the thickness of the soil layer above the ground ice and also by the climate itself.

In general, the nearer ground ice is to the surface, the more it is subjected to temperature extremes and the more fractured it becomes, which leads to smaller polygons.

The simplest explanation about the small polygons is that the first images sent back by Phoenix show a collection of atypically small polygons. A view in another direction may well show the 5-metre polygons that Mellon and other scientists were expecting. (ANI)

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