Just when the world is abuzz about the possibility that the Mars Phoenix Lander will find evidence of liquid water and life-enabling conditions in the prehistoric Martian past, a new report throws a bucket of salty water on that enthusiasm. Researchers studied geochemical findings from the Mars rover Opportunity, and now say that even if liquid water did exist on Mars in a warmer era in the planet’s history, it was probably too salty to support life -- or at least, life as we know it. Martian waters were 10 to 100 times saltier than the Earth's typical seawater, according to the report in Science [subscription required], a salinity level which would kill all organisms that humans know of.
Here on Earth, life seems to have permeated every nook and cranny, from temperate oceans to million-year-old permafrost. But not every environment is hospitable. Curiously enough, it is the food industry that has explored these most extreme conditions. Cram the maximum amount of salt or sugar into a water solution--as in salting meat or making strawberry preserves--and microbes are hard-pressed to survive, much less grow. That's because the ions of dissolved salt hold on to so many water molecules that few are left to support microbial life [ScienceNow Daily News].
While scientists are continually surprised by the harsh conditions that so-called "extremophiles" can withstand, the paper's authors were not optimistic about the prospect of finding evidence of tough little bugs on Mars. "If there was any life on Mars, it would have needed to start off at high acidity and high salinity," said Nicholas Tosca, the paper's lead author and a postdoctoral researcher at Harvard. "[Life on Mars] would require biology that was completely different from any we know on Earth."
...Some microorganisms, known as halophiles (Latin translation: salt lovers), can live in water with [salinity levels as high] as those Tosca believes existed on Mars, but he drew a major distinction between what life could tolerate and what life could begin in. Halophiles on Earth have evolved from less salt-loving ancestors over millions of years, and they didn't originate in such harsh conditions [Wired News].
But some researchers wonder if the patches of dirt sampled by the Mars rover can be representative of the whole planet, and bring a more positive attitude to NASA's continuing quest to "follow the water." Ben Clark, a Mars expert at Lockheed Martin Corporation who was not involved in the study, said the area at the Martian equator sampled by the rovers for this work is already known to be unusual. The region, called Meridiani Planum, was chosen partly for its high content of hematite—an iron oxide mineral—which makes it chemically unique to begin with. Regardless, he said, no single place should be seen as a global representative of Mars's mineral composition.
"It is very difficult to simulate actual Martian conditions," he said. "Whether organisms could evolve to survive or propagate under near-saturated conditions of [salts] is difficult to fully evaluate" [National Geographic News].
Mars may be the main focus for mankind's extraterrestrial longings, but DISCOVER has reported that plenty of other researchers are directing their searches towards life-sustaining planets in other solar systems. The truth is out there -- somewhere. Images: NASA/JPL/Cornell/US Geological Survey
