An image combining orbital imagery with 3-D modeling shows flows that appear in spring and summer on a slope inside Mars' Newton crater. Image credit: NASA/JPL-Caltech/Univ. of Arizona
Observations from NASA's Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.
Dark, finger-like features that appear and extend down some Martian slopes during the warmest months of the Mars year may show activity of salty water on Mars. They fade in the winter, then recur the next spring.
Other explanations remain possible, but flows of liquid brine fit the features' characteristics better than alternative hypotheses. Saltiness lowers the temperature at which water freezes. Some sites with the dark flows get warm enough to keep water liquid if it is about as salty as Earth's oceans, but temperatures in those areas would not melt pure water ice.
Sites with liquid brines could be important to future studies of whether life exists on Mars and to understanding the history of water.
The features are only about 0.5 to 5 yards or meters wide, with lengths up to hundreds of meters. That is much narrower than previously reported gullies on Martian slopes. They have been seen in only about 1 percent as many locations as larger Mars gullies, but some of those locations display more than 1,000 individual flows. Also, while gullies are abundant on cold, pole-facing slopes, these dark flows are not.
The team first discovered the strange features after UA student Lujendra Ojha, at the time a junior majoring in geophysics, used a change detection algorithm capable of identifying subtle changes occurring on the Martian surface over time in image pairs during an independent study project.
"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."
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