By Hamish Johnston
Over the past few years, scientists have discovered more and more evidence that liquid water has shaped the surface of Mars.
However, there is also evidence that the average global temperature on the red planet has been well below the freezing point of water.
So how were those features formed?
Well, anyone who lives in a cold climate knows that adding salt to ice will cause it to melt at a lower temperature than pure water.
Now, an international team of scientists are saying that the same effect could be at work on Mars.
The researchers modelled the freezing and evaporation of Martian water, assuming that it contains the same minerals that had been detected by Martian landers.
They concluded that liquid could indeed flow on Mars at temperatures well below zero Celsius.
The study has just been published in Nature.