Early Mars was cold, wet and...

likely hospitable. This is the conclusion of a recent study of mineral solutions under environmental conditions that exist on Mars:

"Researchers found that solutions containing certain combinations of sulphur, silicon and other ions stay liquid even down to -28 °C – a much more plausible temperature for early Mars than one above 0 °C."

Link to technical abstract: Stability against freezing of aqueous solutions on early Mars.