8 Things You Need To Know About NASA Finding Water On Mars

8. What Are These Dark Streaks?

The seasonal dark streaks on the surface of Mars have long been a cause of excitement amongst NASA scientists for a number of years now. Arguments pinged back and forth as to whether these Recurring Slope Lineae (RSL) were caused by running water or shifting sand.

Now, thanks to some spectral analysis by the Mars Reconnaissance Orbiter on the lines, we're pretty certain that these are caused by what is essentially seasonal melt water - but not as we know it.

Mars is generally speaking pretty cold, with lows of -60°C or so, but as Mars has an axial tilt similar to that of Earth's plus a more eccentric orbit, the surface temperature can vary greatly, with highs in the summer months reaching as much as 20°C near the equator.

It is thought that, during these summer months any water ice locked up in could be melting and vaporising and a type of hydrated salt in the soil known as perchlorates absorb the atmospheric water and lock it into their crystalline structure, allowing the water to exist in its liquid state at much lower temperatures.

It is thought that the streaks are basically left over salt deposits resulting from this process.