NASA’s latest spacecraft to visit Mars, the Mars Reconnaissance Orbiter, has made some stunning observations that show the possibility of flowing water on the red planet. Intriguingly,  repeated observations of the same regions over several Martian seasons show visible changes attributable to some kind of dynamic flow.

[div class=attrib]From NASA / JPL:[end-div]

Observations from NASA’s Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.

“NASA’s Mars Exploration Program keeps bringing us closer to determining whether the Red Planet could harbor life in some form,” NASA Administrator Charles Bolden said, “and it reaffirms Mars as an important future destination for human exploration.”

Dark, finger-like features appear and extend down some Martian slopes during late spring through summer, fade in winter, and return during the next spring. Repeated observations have tracked the seasonal changes in these recurring features on several steep slopes in the middle latitudes of Mars’ southern hemisphere.

“The best explanation for these observations so far is the flow of briny water,” said Alfred McEwen of the University of Arizona, Tucson. McEwen is the principal investigator for the orbiter’s High Resolution Imaging Science Experiment (HiRISE) and lead author of a report about the recurring flows published in Thursday’s edition of the journal Science.

Some aspects of the observations still puzzle researchers, but flows of liquid brine fit the features’ characteristics better than alternate hypotheses. Saltiness lowers the freezing temperature of water. Sites with active flows get warm enough, even in the shallow subsurface, to sustain liquid water that is about as salty as Earth’s oceans, while pure water would freeze at the observed temperatures.

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