In September last year, NASA scientists gave everyone hope of one day finding life on Mars, by presenting the best evidence yet of liquid water on the Red Planet: weird streaks called recurring slope lineae (RSL), which flow down high slopes in warmer seasons.
These RSLs are believed to be related to water because they contain perchlorates—hydrated salts that dramatically lower the freezing point of water, which would mean more rapid melting, and hence, salty flowing water during warm months.
But a new study in Geophysical Research Letters by Christopher Edwards and Sylvain Piqueux says these RSLs may not contain water at all.
Using a thermal imaging instrument on board the Mars Odyssey, Edwards and Piqueux found no significant temperature difference (only about 1 Kelvin) between RSLs and the soil around it, which suggests that they aren’t composed of liquid water at all.
Oddly enough, if the RSLs did contain liquid water, they wouldn’t be cooler than the soil around it, but warmer, because water would fill up interstitial gaps in the soil, and increase its ability to retain heat. Even the presence of ice would do the trick. But sadly, this wasn’t the case.
Best case scenario: the minute temperature difference could theoretically explain the presence of trace amounts of water in RSLs (about 3 percent), making it more like slightly damp sludge (but a very, very damp squib).
Edwards and Piqueux don’t exactly know why RSLs form, but are fairly sure it isn’t caused by flowing liquid water. But that doesn’t mean that there aren’t perchlorates in RSLs. Edwards told The Washington Post they could be present in minute amounts, and may not have necessarily gotten there by liquid water.
What wasn’t addressed in the study was the presence of another kind of salty flowing liquid, not on Mars, but over it: the world’s tears.