Washington, Dec 21 (IANS): Using NASA's Mars Reconnaissance Orbiter (MRO) data, researchers have detected cumulative growth of erosion-carved troughs that may be infant versions of larger features known as Martian "spiders," which are radially patterned channels found only in the south polar region of the Red Planet.

The troughs are resulting from the same thawing-carbon-dioxide process believed to form the spider-like features, the researchers said.

"We have seen for the first time these smaller features that survive and extend from year to year, and this is how the larger spiders get started," said Ganna Portyankina of the University of Colorado, Boulder.

The spiders range in size from tens to hundreds of yards (or meters). Multiple channels typically converge at a central pit, resembling the legs and body of a spider.

The scientists found the results exciting as for the past decade, they checked in vain with MRO's High Resolution Imaging Science Experiment (HiRISE) camera to see year-to-year changes in them.

"These are in sand-dune areas, so we don't know whether they will keep getting bigger or will disappear under moving sand," Portyankina noted.

Dunes appear to be a factor in how the baby spiders form, but they may also keep many from persisting through the centuries needed to become full-scale spiders.

The amount of erosion needed to sculpt a typical spider, at the rate determined from observing active growth of these smaller troughs, would require more than a thousand Martian years.

That is according to an estimate by Portyankina and co-authors in a recent paper published in the journal Icarus.

One Martian year lasts about 1.9 Earth years.

"'Spiders' are a uniquely Martian landform," co-author of the report Candice Hansen of the Planetary Science Institute, Tucson, Arizona, noted.