NASA revealed "the strongest evidence yet that liquid water flows intermittently on present-day Mars" in a news conference Monday, September 28, 2015.

"Our quest on Mars has been to 'follow the water,' in our search for life in the universe, and now we have convincing science that validates what we've long suspected," John Grunsfeld, astronaut and associate administrator of NASA's Science Mission Directorate, said. "This is a significant development, as it appears to confirm that water -- albeit briny -- is flowing today on the surface of Mars."

Alfred McEwen, principal investigator with the University of Arizona, said instead they believe there are "thin layers of wet soil, not standing water," on Mars, but there is "significant volume" on the planet "if you add it all up."

While rain has not been detected, NASA has seen snow. "So there is evidence of a water cycle," a NASA scientist said at Monday's news conference.

Miss today's #MarsAnnouncement? Here's the highlights on evidence that liquid water flows on present-day Mars: https://t.co/sFKSJo7VqD

— NASA (@NASA) September 28, 2015

Watch NASA's Animation of Site of Seasonal Flows in Hale Crater on Mars:

Downhill flows, known as recurring slope lineae (RSL), are possibly related to liquid water on Mars, NASA said.
"The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly. Scientists say it's likely a shallow subsurface flow, with enough water wicking to the surface to explain the darkening."

"We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," said Lujendra Ojha of the Georgia Institute of Technology (Georgia Tech) in Atlanta, lead author of a report on these findings published Sept. 28 by Nature Geoscience.

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