NASA:
New findings from NASA’s Mars Reconnaissance Orbiter (MRO) provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.
Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet. These darkish streaks appear to ebb and flow over time. They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons. They appear in several locations on Mars when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius), and disappear at colder times.
This water is thought to be briny, which keeps the water from freezing at these low temperatures.
“Water on Mars” has been a story for some time now; while this is a new discovery, we’ve known of ice on the Red Planet for years. It’s unclear where this water is from, and it doesn’t make Mars more hospitable to human life, but it sure is fun to learn more about our neighbor Mars.