We are very interested in the possibility of water on Mars because where there is water there is the potential for life. But a new study throws a bit of a damp ceiling (pun intended) on this tantalizing possibility. Unfortunately, it looks like even the salty brine can only exist on the surface of Mars for a few hours.
Water is a very difficult thing to keep in a liquid state. Despite the fact that it is the most common molecule in the universe, it is almost always frozen as ice or evaporated into a gas.
Usually, liquid water needs something to keep it in the correct pressure and temperature range. On Earth we have a thick atmosphere and some moons in the outer solar system have thick ice shells.
But Mars doesn't have either, and although there was abundant water on its surface billions of years ago, there is likely nothing left. Even so, astronomers have looked for signs of moisture on the surface, particularly in the form of saline solutions: super-saline solutions that, despite the extremely low pressure and cold temperatures, contain enough chemicals to keep the water in a liquid state.
While those searches were inconclusive, Earthbound scientists have been looking for ways to test the possibility: building Mars simulation chambers like the one at the University of Arkansas.
The researchers combined data from these simulations and maps of all the sunlight on Mars and delivered some dire news: brines don't like it on the red planet either.
Taking into account all possible phase changes of water, including freezing, melting, and evaporation, the researchers found that previous studies consistently overestimated the stability of saline solutions. Even in the middle latitudes, where the chances are highest, brines can survive on the surface for a maximum of 12 hours.
It's not even a full day. If there's life on Mars, it's not having a good time.