It's a flow chart from another world. NASA's Mars Reconnaissance Orbiter has found the best evidence yet that liquid water streams along the planet's surface during warm seasons. Recurring slope lineae (RSL) -dark streaks that appear, grow and then fade each Martian year - were discovered in 2011, and appeared to signify flowing water. Now data from the orbiter"s spectrometer, which can help identify surface minerals, would appear to back that idea. Spectral measurements from four RSL sites reveal the presence of hydrated salts - probably magnesium perchlorate, magnesium chlorate and sodium perchlorate - that can absorb water from the atmosphere and lower its freezing point, letting it stay liquid even in Mars's cold climate (Nature Ceoscience, doi.org/7xw).
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