Images snapped by a NASA satellite point to the possibility of seasonal liquid water on the Red Planet’s surface -- water on Mars, the space agency announced Thursday.
Observations by the High Resolution Imaging Science Experiment (HiRISE) camera aboard the orbiting Mars Reconnaissance Orbiter (MRO) have captured recurring features on several steep slopes in Mars’ southern hemisphere, which researchers believe could be evidence of water.
"This is water today, not in the past," study co-author Alfred McEwen, a planetary scientist at the University of Arizona, told SPACE.com.
“The best explanation we have for these observations so far is flow of briny water,” said McEwen, who was quick to clarify that "this study does not prove that." The scientist is the principal investigator for the orbiter's HiRISE camera and the lead author of a report about the recurring flows published on August 5 by the journal Science.
The substance is far from the ice known to exist on Mars or ordinary liquid water, however.
"It's more like a syrup in how it flows," McEwen explained. "We really don't know how salty it is from these observations." Or if it's water at all: The evidence so far is by no means definitive proof but scientists are hard-pressed to find meaningful alternative theories.
“By comparison with Earth, it's hard to imagine they are formed by anything other than fluid seeping down slopes,” said MRO project scientist Richard Zurek of NASA's Jet Propulsion Laboratory, in Pasadena, Calif. “The question is whether this is happening on Mars and, if so, why just in these particular places.”
While frozen water has been detected underground, these recurring dark flows could be the first known Martian ground with liquid water, according to researchers.
"NASA's Mars Exploration Program keeps bringing us closer to determining whether the Red Planet could harbor life in some form," said NASA Administrator Charles Bolden. "And it reaffirms Mars as an important future destination for human exploration."
The potentially groundbreaking study was first discovered by University of Arizona student Lujendra Ojha, then a junior majoring in geophysics. Ojha was studying subtle changes on the planet’s surface as an independent study project when he noticed the strange seasonal features.
“I was baffled when I first saw those features in the images after I had run them through my algorithm,” said Ojha, who is a co-author on the Science publication. “We soon realized they were different from slope streaks that had been observed before. These are highly seasonal, and we observed some of them had grown by more than 200 meters in a matter of just two Earth months.”
For the team, this is just the beginning. When the researchers checked the flow-marked slopes with the orbiter’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), it detected no signs of water.
But that doesn’t rule out the possibility that any liquid may quickly dry on the surface, or that these are actually shallow subsurface flows.
“The flows are not dark because of being wet,” McEwen said. “A flow initiated by briny water could rearrange grains or change surface roughness in a way that darkens the appearance. How the features brighten again when temperatures drop is harder to explain.”
“It's a mystery now, but I think it's a solvable mystery with further observations and experiments,” he said.