After finding strong evidence supporting the presence of lake, river and glacier once upon a time on Mars, scientists have now found indirect evidence to support the presence of transient liquid water brine (very salty water) on Mars.
The brine is likely to be present in the uppermost 5 cm of the Mars soil from sunset to sunrise during winter and for shorter windows of time during other seasons.
At night, some of the water vapour in the atmosphere condenses as frost. Calcium perchlorate salt, which is globally present on Mars, absorbs the frost and forms brine by reducing the freezing temperature of water.
The inference of transient liquid water on the red planet was based on the analysis of relative humidity, air temperature, and ground temperature data collected by Curiosity from the Gale Crater over one full Martian year. The results were published on April 13, 2015 in the journal Nature Geoscience .
Too low to support lifeThe authors state that the water activity and temperature are “probably low” to support any form of terrestrial life. Also, the transient nature of water is not conducive for the replication and metabolism of terrestrial micro-organisms.
Since the data collected by Curiosity is from the equator, the driest and warmest region of the red planet, the possibility of abundant brines in other regions of the planet is high due to greater atmospheric water content in the form of humidity and lower temperature.
The presence of brine also affects the solubility of other salts in the uppermost 15 cm of soil.
Data collected by Curiosity suggest a two-layer model — a drier uppermost layer “several centimetres thick” and a wetter layer beneath. The average depth of the transition from a dry uppermost layer to a wet layer beneath it is 17 cm.
