Flowing, salty water has been discovered on Mars during the planet's warmest season, NASA confirms.
For years, scientists had observed dark streaks on the surface of Mars form during the spring, grow through the summer and disappear in the fall. But they didn't have an explanation until using an imaging spectrometer aboard the Mars Reconnaissance Orbiter.
The instrument detected hydrated salts on slopes where mysterious streaks are seen. Scientists realized that the water was flowing down the slopes of formations like craters when temperatures are above minus 10 degrees Fahrenheit.
Salts lower the freezing temperature of the water, meaning it could flow as liquid even at that low temperature.
"The detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," said Lujendra Ojha, the lead author of the report published Monday in Nature Geoscience.
"Today's announcement of a really fascinating result about current water on Mars is one of the reasons why I feel its even more imperative that we send astrobiologists and planetary scientists to Mars to explore the question of, 'Is there current life on Mars?'" said John Grunsfeld, Associate Administrator of NASA Science Mission Directorate.
Grunsfeld said the surface of Mars was once like Earth, with warm, salty seas and freshwater lakes. He said it also probably had snowcapped peaks, clouds and a water cycle just like ours.
This discovery, Grunsfeld said, makes it possible that life could exist today on Mars to be discovered by a future rover or manned mission.
"Discovery is why we do science," Grunsfeld said. "We're trying to answer fundamental questions about our universe, about our home planet, about our solar system."
Jim Green, Planetary Science Division Director, said that three billion years ago the Martian ocean may have been up to one mile deep and could have covered two-thirds of the planet's northern hemisphere.
"But something happened, Mars suffered a major climate change and lost its surface water," Green said.
Still, he said the air on the planet has more humidity than expected and the soils are moist -- albeit briny.