Because Mars is very cold it is not known how water could be flowing liquid form. However, it is believed that high salt content of the water may be inhibiting freezing. Another theory is that the water is being heated under ground and gushing up to the surface, where it flows before freezing.
Mars has been known for a long time to have polar ice caps but the latest photographic data is the first evidence that liquid water might exist on the planet.
Plans are underway to focus in on further studies of the area where the gullies have formed.