LOS ANGELES - A researcher has spotted lava flows shaped like coils of rope near the equator of Mars, the first time such features have been discovered on another planet.
These twisty volcanic patterns can be found on Hawaii's Big Island and in the Pacific seafloor. While evidence for lava flows is present in many places on Mars, none is shaped like this latest find.
"I was quite surprised and puzzled when I first saw the coils," Andrew Ryan, a graduate student at Arizona State University, said in an email. He reported the discovery in Friday's issue of the journal Science.
The biggest surprise? The largest Martian lava spiral measured 100 feet across - bigger than any on Earth. It is further evidence that Mars was volcanically active recently - geologically speaking, within the past 20 million years.
For more than a decade, scientists debated whether this maze of valleys near the Martian equator was sculpted by ice or volcanic processes.
As part of a class project last year, Ryan analyzed about 100 high-resolution photos of the region snapped by the Mars Reconnaissance Orbiter, which has been photographing the Martian surface since 2006. One evening, while taking a second look at the images, Ryan zoomed in and noticed the lava coils. He counted 269 spirals ranging from 16 feet to 100 feet across.
Ryan said he was not surprised the features were overlooked in the past since they blended in with the terrain. The coils looked strikingly similar to Hawaiian lava flows, leading Ryan to conclude that lava - not ice - was the driving force.
Planetary scientist David Paige of UCLA said the new work provides convincing evidence that the curious patterns were forged from volcanic activity.
This "illustrates just how complicated Mars' geologic history appears to really be," Paige wrote in an email. He was not part of the research team.
It's believed that rivers of lava flowed through the Martian valleys into a broad basin where they settled and formed the coil shapes. The spiral shapes were preserved as the lava cooled.
There are no clear signs that the region is volcanically active today. With more observations, Ryan said, it is possible lava coils may be found elsewhere on the red planet.