Washington, September 17 : A new research has suggested that surface water may have existed in some parts of the Martian landscape a billion years longer than previous studies have shown.
Catherine Weitz, a senior scientist with the Planetary Science Institute, along with her team, led the research.
This presents strong evidence that sustained and large-scale processes associated with precipitation and flowing water likely occurred on the plains surrounding Valles Marineris during the Hesperian Epoch, 3 to 3.7 billion years ago.
Valles Marineris is a huge canyon system that runs nearly a quarter of the way around the planet at its equator.
According to many studies, runoff from precipitation ceased by the end of the Noachian Epoch, which spanned the first billion years of Martian history.
But, after studying HiRISE images of light-toned layered deposits on the plains surrounding Valles Marineris, Weitz and her co-authors concluded that equatorial regions may have remained wet for a much longer period.
Scientists have studied the light-toned layered deposits inside Valles Marineris since the Mariner flybys in the early 1970s, but the HiRISE camera flying aboard the Mars Reconnaissance Orbiter has now given them an unparalleled, close-up view of the planet's features.
HiRISE can resolve objects as small as three feet in diameter.
Weitz questioned whether the light-toned layered deposits on the plains surrounding Valles Marineris were different from those inside Valles Marineris. Two years ago, she began aiming the HiRISE camera to photograph these layered deposits.
"What we found was that these light-toned layered deposits on the plains are very different from those within Valles Marineris," Weitz said.
"There are a lot of variations in brightness, color, and erosional properties that we don't see for light-toned deposits inside Valles Marineris. This suggests that the processes that created the deposits outside Valles Marineris were different from those operating inside," she added.
Weitz found light-toned layered deposits associated with valley systems and inverted channels in two locations near Valles Marineris.
Weitz and her colleagues also have found valley systems that probably were created by running water in two other areas of light-toned layered deposits adjacent to Valles Marineris.
All of these phenomena point toward what geologists call fluvial processes - those associated with running water.
"This was a big surprise because no one thought we'd be seeing these extensive fluvial systems in the plains all around Valles Marineris that were formed during the Hesperian Era," Weitz said. "Everyone thought that by then the climate had pretty much dried out," she added.
"What we're seeing tells us that this light-toned layering on the plains was associated with fluvial activity that wasn't occurring just in little pockets over very brief episodes, but rather on a much larger scale for sustained time periods," said Weitz.