January 29, 2013
More Evidence Rolls In Of Ancient Riverbed On Mars
Lee Rannals for redOrbit.com — Your Universe Online
Brown University researchers found networks of narrow ridges in impact craters on Mars that appear to be fossilized remnants of underground cracks through which water once flowed.
The study adds more weight to the growing pile of evidence Mars once had an active hydrology and could be a good place to search for evidence of ancient life.
The ridges had been noted in previous research, but how they had formed was not known. Researchers decided they might once have been faults and fractures that formed underground when impact events rattled the planet.
Water, if present during the time, would have circulated through the cracks, slowly filling them with mineral deposits, which would have been harder than the surrounding rocks. Those surrounding rocks eroded away over millions of years and the seams of mineral-hardened material would remain in place.
In order to test their hypothesis, the team mapped over 4,000 ridges in two crater-rocked regions on Mars. They used high-resolution images from NASA's Mars Reconnaissance Orbiter, and noted the orientations of the ridges and composition of the surrounding rocks.
The data used was consistent with the idea the ridges started out as fractures formed by impact events. Another hypothesis suggests these structures have been sheets of volcanic magma intruding into the surrounding rock.
Orientations were similar to the alignments of large faults related to mega-scale impacts at another spot on Mars.
“This suggests that fracture formation resulted from the energy of localized impact events and are not associated with regional-scale volcanism,” Lee Saper, a recent Brown graduate, said in a statement.
The team also found the ridges exist exclusively in areas where the surrounding rock is rich in iron-magnesium clay, a mineral considered to be a sign water had once been present in the rocks.
“The association with these hydrated materials suggests there was a water source available,” Saper explained. “That water would have flowed along the path of least resistance, which in this case would have been these fracture conduits.”
The results suggest the ancient Martian subsurface and flowing water may have offered up a habitable environment on the Red Planet.
“This gives us a point of observation to say there was enough fracturing and fluid flow in the crust to sustain at least a regionally viable subsurface hydrology,” Saper said. “The overarching theme of NASA´s planetary exploration has been to follow the water. So if in fact these fractures that turned into these ridges were flowing with hydrothermal fluid, they could have been a viable biosphere.”
Currently, NASA's Curiosity rover is rolling around on Mars while trying to uncover some of the evidence of ancient life. Saper hopes this new tool will be able to shed more light on this rising research.
“In the site at Gale Crater, there are thought to be mineralized fractures that the rover will go up and touch,” Saper said in the statement. “These are very small and may not be exactly the same kind of feature we studied, but we´ll have the opportunity to crush them up and do chemical analysis on them. That could either bolster our hypothesis or tell us we need to explore other possibilities.”