New findings from NASA's Mars Reconnaissance Orbiter (MRO) provide a strong evidence that liquid water flows intermittently on the present-day Mars. The findings were published in the journal Nature Geoscience on 28 September 2015.
The researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet using an imaging spectrometer on MRO.
These darkish streaks appear to fade 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 and disappear at colder times.
These downhill flows known as Recurring Slope Lineae (RSL), often have been described as possibly related to liquid water.
Garni crater on Mars
Dark narrow streaks called Recurring Slope Lineae originate out of the walls of Garni crater on Mars. The dark streaks here are up to few hundred meters in length. They are hypothesized to be formed by flow of briny liquid water on Mars.
The detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks. The spectrometer observations show signatures of hydrated salts at multiple RSL locations, but only when the dark features were relatively wide.
When the researchers looked at the same locations and RSL weren't as extensive, they detected no hydrated salt. The MRO's High Resolution Imaging Science Experiment (HiRISE) observations now have documented RSL at dozens of sites on Mars.
The scientists interpret that the spectral signatures were caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate.
Perchlorates have previously been seen on Mars.
There is a strong evidence for hydrated salts at all four locations in the seasons when recurring slope lineae are most extensive, which suggests that the source of hydration is recurring slope lineae activity. The findings strongly support the hypothesis that recurring slope lineae form as a result of contemporary water activity on Mars.
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What: Found by NASA scientists
When: 28 September 2015