April 27, 2012
Lava Flows On Mars Resemble Patterns On Earth
Lee Rannals for RedOrbit.com
The lava flows reveal coiling spiral patterns that resemble snail or nautilus shells, according to research published in the scientific journal Science on Friday.
On Earth, lava coils can be found on the Big Island of Hawaii, mainly on the surface of ropey pahoehoe lava flows. They can also be seen in submarine lava flows near the Galapagos Rift on the Pacific Ocean floor.
"The coils form on flows where there's a shear stress – where flows move past each other at different speeds or in different directions," Arizona State University graduate student Andrew Ryan, who made the discovery, said in a press release. "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."
He said that scientists have similarly documented the formation of rotated pieces of oceanic crust and mid-ocean ridge spreading centers.
"Since the surface of active lava lakes, such as those on Hawaii, can have crustal activity like spreading centers do, it's conceivable that lava coils may form there in a similar way, but at a smaller scale," Ryan said.
The size of the Martian lava coil came as a surprise. According to Ryan, the largest lava coil on the Red Planet is about 100-feet across, which is bigger than any known lava coils on Earth.
The researchers have documented nearly 200 lava coils in the Cerberus Palus region alone.
"Lava coils may be present in other Martian volcanic provinces or in outflow channels mantled by volcanic features," Ryan said. "I expect that we'll find quite a few more in Elysium as the HiRISE image coverage grows over time."
The discovery came out of research into possible interactions of lava flows and floods of water in the Elysium volcanic province of Mars.
"I was interested in Martian outflow channels and was particularly intrigued by Athabasca Valles and Cerberus Palus, both part of Elysium," Ryan said. "Athabasca Valles has a very interesting history. There's an extensive literature on the area, as well as an intriguing combination of seemingly fluvial and volcanic features."
Among the features Ryan observed were large slabs or plates that resemble broken floes of park ice in the Arctic Ocean on Earth. Some scientists have argued before that the plates in Elysium are actually underlain by water ice.
Ryan said it was these claims that led him to study this year, but he became fascinated by the terrain lying between the plates after taking infrared temperatures.
"One evening," Ryan said, "I was making a second pass over the HiRISE images when I first noticed puzzling spiral patterns in an image near the southern margin of Cerberus Palus.
He said he almost overlooked this frame because he thought it might not be too useful because it was so far away from the main study area.
"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," he said in the press release.
"I don't find it surprising that these were overlooked in the past. I nearly missed them too."
Image 1: Cooling lava on Mars can form patterns like snail shells when the lava is pulled in two directions at once. Such patterns, rare on Earth, have never before been seen on Mars. This image, with more than a dozen lava coils visible, shows an area in a volcanic region named Cerberus Palus that is about 500 meters (1640 feet) wide. Photo by: NASA/JPL-Caltech/UA
Image 2: Newer lava lying between two older plates of rough, hardened lava was still hot and plastic enough to form coils and spirals when the plates slid past one another. This image shows an area about 360 meters (1200 feet) wide in Cerberus Palus. Photo by: NASA/JPL-Caltech/UA