hiddenApr 27, 2012 15:30:42 IST
A researcher at Arizona State University in the US claims to have spotted a new form of lava flow - shaped like coils of rope - near the equator of Mars.
Andrew Ryan says in the Science journal that such coiling spiral patterns of lava flows that resemble snail or nautilus shells have been found in a few locations on Earth, but never before on Mars.
"I was interested in Martian outflow channels and was particularly intrigued by Athabasca Valles and Cerberus Palus, both part of Elysium. Athabasca Valles has a very interesting history," Ryan said.
He added, "There's an extensive literature on the area, as well as an intriguing combination of seemingly fluvial and volcanic features."
Among the features are large slabs or plates that resemble broken floes of pack ice in the Arctic Ocean on Earth. In the past, a few scientists have argued that the plates in Elysium are in fact underlain by water ice.
Assessing those claims that ice was present today beneath the lava plates drove Ryan to study the area. "I examined probably 100 HiRISE images of the area," Ryan said, referring to the High Resolution Imaging Science Experiment camera on the Mars Reconnaissance Orbiter.
He added, "The coils become noticeable in the full-resolution HiRISE image only when you really zoom in. They also tend to blend in with the rest of the light-gray terrain - that is, until you stretch the contrast a bit."
On Earth, lava coils can be found on the Big Island of Hawaii, mainly on the surface of ropey pahoehoe lava flows.
They have also been seen in submarine lava flows near the Galapagos Rift on the Pacific Ocean floor.
Ryan said, "The coils form on flows where there's a shear stress - where flows move past each other at different speeds or in different directions. Pieces of rubbery and plastic lava crust can either be peeled away and physically coiled up - or wrinkles in the lava's thin crust can be twisted around."
The size of Martian lava coils came as a surprise. "On Mars the largest lava coil is 30 meters across - that's 100 feet. That's bigger than any lava coils on Earth.