Water on Mars Too Salty for Life

Water on Mars Too Salty for Life

I always know when our water purification system isn’t working right. All it takes is a gulp of water from the kitchen tap.

The intense salty taste followed by spewed water in the sink is a telltale sign that the system isn’t properly washing the column with the liquid from the brine tank.

Salty water is not good to drink—and it’s distasteful for life. Living organisms can tolerate only so much salt. In fact, because of its antimicrobial effects salt is used to cure and preserve meat. High salt in the milieu kills by drawing water out of the microbial cells through the process of osmosis.

New research indicates that salt may have acted as a preservative of sorts on Mars, preventing life from taking hold early in its history.

Astrobiologists focus a lot of attention on detecting life (and/or the remains of ancient life) on Mars. Many scientists argue that if life exists on Mars, particularly if it’s distinct from Earth life, then it validates the evolutionary paradigm. Unique Martian life-forms would seemingly imply that life had arisen twice, once on Earth and once on Mars.

Evidence for ancient life on Mars carries implications for the origin of life on Earth. As Hugh Ross and I discuss in Origins of Life life’s first appearance on Earth is enigmatic within the evolutionary paradigm. Instead of life emerging gradually over a vast period of time (several hundred million years), it appears suddenly as soon as the Earth can sustain it. And the first life on Earth is remarkably complex, metabolically speaking. This makes little sense from an evolutionary perspective, prompting some origin-of-life researchers to speculate that perhaps life originated on Mars very early in its history and was transported to Earth on Martian meteors. Accordingly, life’s first appearance on Earth about 3.8 billion years ago was not an origination event, but the arrival of life from Mars. If it was transported to Earth, it would seem as if it appeared suddenly in the geological record.

Support for this idea comes from the discovery that ancient Mars was a warm, wet planet. But just because Mars once harbored liquid water on its surface doesn’t necessarily mean that life existed on the Red Planet. Liquid water is only one requirement for life. The temperature, pH, and salinity of the water impact habitability.

Recently a team of astrobiologists from Harvard University determined that the salinity of the water on early Mars, as far back as 4 billion years ago, would have rendered the planet uninhabitable. The water on early Mars appears to have been much saltier than Earth’s sea water. In fact, the water on Mars must have been saltier than bodies of water that harbor halophiles, salt-loving microbes that thrive in high saline environments.

Previous work has demonstrated that high salt levels interfere with the assembly of RNA molecules on mineral surfaces, a central idea in the RNA World hypothesis for the origin of life. Large quantities of salt also frustrate the assembly of fatty acids into primitive cell membranes. These are two key stages in most origin-of-life pathways.

The idea that life existed or originated on Mars early in its history has just been spewed into the sink. The water is way too salty.