When the news broke out that Mars have liquid water, I was often asked by my colleagues(from the non-scientific community) on what the ramification is. Well, it is the fact that liquid water is an amniotic fluid for life. But let me start by accounting the physics behind it.
Liquid water on Mars was thought to be unlikely existing(at least that is how it goes for the last 3 billion years). And as far we see, considering the two culprits,1) thin atmosphere 2) extremely cold temperature and varies similarly extremely over similarly extremely short span of time, makes the liquid water impossible to exist for more than few hours.
Not only that the atmospheric pressure to be less than 0.7% than that of Earth, the Martian dunes are frozen, and gets immediately dried up, bypassing liquid phase. On Earth, the atmospheric pressure is high enough such hat water will be in a liquid state under 270- 370 Kelvin(Earth's typical average temperature range), so water is abundant. But on Mars, the atmospheric pressure is somewhere between 0.6% and 1.0% than that of Earth, or between 100 and 150 times smaller. Mars is also much colder than Earth, so that these two factors combined means that there’s either never liquid water on Mars, and it goes from solid ice straight to water vapor when it gets warm (and back again when it gets cold), or it can be liquid water for a very narrow temperature range that only occurs very infrequently on Mars.
But the question is, has Mars ever possess that temperature in its entire existence? Perhaps not, but while the average temperature of Mars may have been different in the past, there was never a larger atmosphere and the temperature was never stable. So we infer, to some point, that Mars could never have had a stable ocean, river stream or any body of water for that instance; the best it could have was an ice-bed that melts during the day, and lucky enough not to boil, and suddenly evaporate.
So it was a twist of thought process when NASA(from the Mars Reconnaissance Orbiter data) announced(and confirmed) the discovery of liquid water on Mars. Not only did the red planet has a watery past, leaving us with a number of distinctive features that could only arise from liquid flowing on its surface, including dried-up riverbeds, martian spherules, dozens of layers of sedimentary rock, canyons that show evidence of being formed by water-based erosion, and frozen lakes, icecaps, and sub-surface ice.
But we have already had a previous understanding to explain the physics of its planetary condition, so what could be the smoking gun for its trace mount of moisture and liquid water indications? Since there are hints of flowing water, could life have once sustained(or is currently sustained in the form of microbes) in Mars? But how come it has liquid water. The answer maybe staring us in the face. An antifreeze that is a common household ingredient, "salt". It's this briny substrate that will hold moisture in otherwise barren environment.
So let's keep abreast and see where the probe will lead us.
Photos used in these articles are merely grabbed from the internet